text: /*-------------------------------------------------------------------------
   *
   * allpaths.c
   *	  Routines to find possible search paths for processing a query
   *
   * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  src/backend/optimizer/path/allpaths.c
   *
   *-------------------------------------------------------------------------
   */
  
  #include "postgres.h"
  
  #include <limits.h>
  #include <math.h>
  
  #include "access/sysattr.h"
  #include "access/tsmapi.h"
  #include "catalog/pg_class.h"
  #include "catalog/pg_operator.h"
  #include "catalog/pg_proc.h"
  #include "foreign/fdwapi.h"
  #include "miscadmin.h"
  #include "nodes/makefuncs.h"
  #include "nodes/nodeFuncs.h"
  #ifdef OPTIMIZER_DEBUG
  #include "nodes/print.h"
  #endif
  #include "optimizer/clauses.h"
  #include "optimizer/cost.h"
  #include "optimizer/geqo.h"
  #include "optimizer/pathnode.h"
  #include "optimizer/paths.h"
  #include "optimizer/plancat.h"
  #include "optimizer/planner.h"
  #include "optimizer/prep.h"
  #include "optimizer/restrictinfo.h"
  #include "optimizer/tlist.h"
  #include "optimizer/var.h"
  #include "parser/parse_clause.h"
  #include "parser/parsetree.h"
  #include "rewrite/rewriteManip.h"
  #include "utils/lsyscache.h"
  
  
  /* results of subquery_is_pushdown_safe */
  typedef struct pushdown_safety_info
  {
  	bool	   *unsafeColumns;	/* which output columns are unsafe to use */
  	bool		unsafeVolatile; /* don't push down volatile quals */
  	bool		unsafeLeaky;	/* don't push down leaky quals */
  } pushdown_safety_info;
  
  /* These parameters are set by GUC */
  bool		enable_geqo = false;	/* just in case GUC doesn't set it */
  int			geqo_threshold;
  int			min_parallel_table_scan_size;
  int			min_parallel_index_scan_size;
  
  /* Hook for plugins to get control in set_rel_pathlist() */
  set_rel_pathlist_hook_type set_rel_pathlist_hook = NULL;
  
  /* Hook for plugins to replace standard_join_search() */
  join_search_hook_type join_search_hook = NULL;
  
  
  static void set_base_rel_consider_startup(PlannerInfo *root);
  static void set_base_rel_sizes(PlannerInfo *root);
  static void set_base_rel_pathlists(PlannerInfo *root);
  static void set_rel_size(PlannerInfo *root, RelOptInfo *rel,
  			 Index rti, RangeTblEntry *rte);
  static void set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
  				 Index rti, RangeTblEntry *rte);
  static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
  				   RangeTblEntry *rte);
  static void create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel);
  static void set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
  						  RangeTblEntry *rte);
  static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
  					   RangeTblEntry *rte);
  static void set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel,
  						 RangeTblEntry *rte);
  static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
  							 RangeTblEntry *rte);
  static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
  				 RangeTblEntry *rte);
  static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
  					 RangeTblEntry *rte);
  static void set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
  					Index rti, RangeTblEntry *rte);
  static void set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
  						Index rti, RangeTblEntry *rte);
  static void generate_mergeappend_paths(PlannerInfo *root, RelOptInfo *rel,
  						   List *live_childrels,
  						   List *all_child_pathkeys,
  						   List *partitioned_rels);
  static Path *get_cheapest_parameterized_child_path(PlannerInfo *root,
  									  RelOptInfo *rel,
  									  Relids required_outer);
  static List *accumulate_append_subpath(List *subpaths, Path *path);
  static void set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
  					  Index rti, RangeTblEntry *rte);
  static void set_function_pathlist(PlannerInfo *root, RelOptInfo *rel,
  					  RangeTblEntry *rte);
  static void set_values_pathlist(PlannerInfo *root, RelOptInfo *rel,
  					RangeTblEntry *rte);
  static void set_tablefunc_pathlist(PlannerInfo *root, RelOptInfo *rel,
  					   RangeTblEntry *rte);
  static void set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel,
  				 RangeTblEntry *rte);
  static void set_namedtuplestore_pathlist(PlannerInfo *root, RelOptInfo *rel,
  							 RangeTblEntry *rte);
  static void set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel,
  					   RangeTblEntry *rte);
  static RelOptInfo *make_rel_from_joinlist(PlannerInfo *root, List *joinlist);
  static bool subquery_is_pushdown_safe(Query *subquery, Query *topquery,
  						  pushdown_safety_info *safetyInfo);
  static bool recurse_pushdown_safe(Node *setOp, Query *topquery,
  					  pushdown_safety_info *safetyInfo);
  static void check_output_expressions(Query *subquery,
  						 pushdown_safety_info *safetyInfo);
  static void compare_tlist_datatypes(List *tlist, List *colTypes,
  						pushdown_safety_info *safetyInfo);
  static bool targetIsInAllPartitionLists(TargetEntry *tle, Query *query);
  static bool qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
  					  pushdown_safety_info *safetyInfo);
  static void subquery_push_qual(Query *subquery,
  				   RangeTblEntry *rte, Index rti, Node *qual);
  static void recurse_push_qual(Node *setOp, Query *topquery,
  				  RangeTblEntry *rte, Index rti, Node *qual);
  static void remove_unused_subquery_outputs(Query *subquery, RelOptInfo *rel);
  static void add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
  						List *live_childrels);
  
  
  /*
   * make_one_rel
   *	  Finds all possible access paths for executing a query, returning a
   *	  single rel that represents the join of all base rels in the query.
   */
  RelOptInfo *
  make_one_rel(PlannerInfo *root, List *joinlist)
  {
  	RelOptInfo *rel;
  	Index		rti;
  
  	/*
  	 * Construct the all_baserels Relids set.
  	 */
  	root->all_baserels = NULL;
  	for (rti = 1; rti < root->simple_rel_array_size; rti++)
  	{
  		RelOptInfo *brel = root->simple_rel_array[rti];
  
  		/* there may be empty slots corresponding to non-baserel RTEs */
  		if (brel == NULL)
  			continue;
  
  		Assert(brel->relid == rti); /* sanity check on array */
  
  		/* ignore RTEs that are "other rels" */
  		if (brel->reloptkind != RELOPT_BASEREL)
  			continue;
  
  		root->all_baserels = bms_add_member(root->all_baserels, brel->relid);
  	}
  
  	/* Mark base rels as to whether we care about fast-start plans */
  	set_base_rel_consider_startup(root);
  
  	/*
  	 * Compute size estimates and consider_parallel flags for each base rel,
  	 * then generate access paths.
  	 */
  	set_base_rel_sizes(root);
  	set_base_rel_pathlists(root);
  
  	/*
  	 * Generate access paths for the entire join tree.
  	 */
  	rel = make_rel_from_joinlist(root, joinlist);
  
  	/*
  	 * The result should join all and only the query's base rels.
  	 */
  	Assert(bms_equal(rel->relids, root->all_baserels));
  
  	return rel;
  }
  
  /*
   * set_base_rel_consider_startup
   *	  Set the consider_[param_]startup flags for each base-relation entry.
   *
   * For the moment, we only deal with consider_param_startup here; because the
   * logic for consider_startup is pretty trivial and is the same for every base
   * relation, we just let build_simple_rel() initialize that flag correctly to
   * start with.  If that logic ever gets more complicated it would probably
   * be better to move it here.
   */
  static void
  set_base_rel_consider_startup(PlannerInfo *root)
  {
  	/*
  	 * Since parameterized paths can only be used on the inside of a nestloop
  	 * join plan, there is usually little value in considering fast-start
  	 * plans for them.  However, for relations that are on the RHS of a SEMI
  	 * or ANTI join, a fast-start plan can be useful because we're only going
  	 * to care about fetching one tuple anyway.
  	 *
  	 * To minimize growth of planning time, we currently restrict this to
  	 * cases where the RHS is a single base relation, not a join; there is no
  	 * provision for consider_param_startup to get set at all on joinrels.
  	 * Also we don't worry about appendrels.  costsize.c's costing rules for
  	 * nestloop semi/antijoins don't consider such cases either.
  	 */
  	ListCell   *lc;
  
  	foreach(lc, root->join_info_list)
  	{
  		SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
  		int			varno;
  
  		if ((sjinfo->jointype == JOIN_SEMI || sjinfo->jointype == JOIN_ANTI) &&
  			bms_get_singleton_member(sjinfo->syn_righthand, &varno))
  		{
  			RelOptInfo *rel = find_base_rel(root, varno);
  
  			rel->consider_param_startup = true;
  		}
  	}
  }
  
  /*
   * set_base_rel_sizes
   *	  Set the size estimates (rows and widths) for each base-relation entry.
   *	  Also determine whether to consider parallel paths for base relations.
   *
   * We do this in a separate pass over the base rels so that rowcount
   * estimates are available for parameterized path generation, and also so
   * that each rel's consider_parallel flag is set correctly before we begin to
   * generate paths.
   */
  static void
  set_base_rel_sizes(PlannerInfo *root)
  {
  	Index		rti;
  
  	for (rti = 1; rti < root->simple_rel_array_size; rti++)
  	{
  		RelOptInfo *rel = root->simple_rel_array[rti];
  		RangeTblEntry *rte;
  
  		/* there may be empty slots corresponding to non-baserel RTEs */
  		if (rel == NULL)
  			continue;
  
  		Assert(rel->relid == rti);	/* sanity check on array */
  
  		/* ignore RTEs that are "other rels" */
  		if (rel->reloptkind != RELOPT_BASEREL)
  			continue;
  
  		rte = root->simple_rte_array[rti];
  
  		/*
  		 * If parallelism is allowable for this query in general, see whether
  		 * it's allowable for this rel in particular.  We have to do this
  		 * before set_rel_size(), because (a) if this rel is an inheritance
  		 * parent, set_append_rel_size() will use and perhaps change the rel's
  		 * consider_parallel flag, and (b) for some RTE types, set_rel_size()
  		 * goes ahead and makes paths immediately.
  		 */
  		if (root->glob->parallelModeOK)
  			set_rel_consider_parallel(root, rel, rte);
  
  		set_rel_size(root, rel, rti, rte);
  	}
  }
  
  /*
   * set_base_rel_pathlists
   *	  Finds all paths available for scanning each base-relation entry.
   *	  Sequential scan and any available indices are considered.
   *	  Each useful path is attached to its relation's 'pathlist' field.
   */
  static void
  set_base_rel_pathlists(PlannerInfo *root)
  {
  	Index		rti;
  
  	for (rti = 1; rti < root->simple_rel_array_size; rti++)
  	{
  		RelOptInfo *rel = root->simple_rel_array[rti];
  
  		/* there may be empty slots corresponding to non-baserel RTEs */
  		if (rel == NULL)
  			continue;
  
  		Assert(rel->relid == rti);	/* sanity check on array */
  
  		/* ignore RTEs that are "other rels" */
  		if (rel->reloptkind != RELOPT_BASEREL)
  			continue;
  
  		set_rel_pathlist(root, rel, rti, root->simple_rte_array[rti]);
  	}
  }
  
  /*
   * set_rel_size
   *	  Set size estimates for a base relation
   */
  static void
  set_rel_size(PlannerInfo *root, RelOptInfo *rel,
  			 Index rti, RangeTblEntry *rte)
  {
  	if (rel->reloptkind == RELOPT_BASEREL &&
  		relation_excluded_by_constraints(root, rel, rte))
  	{
  		/*
  		 * We proved we don't need to scan the rel via constraint exclusion,
  		 * so set up a single dummy path for it.  Here we only check this for
  		 * regular baserels; if it's an otherrel, CE was already checked in
  		 * set_append_rel_size().
  		 *
  		 * In this case, we go ahead and set up the relation's path right away
  		 * instead of leaving it for set_rel_pathlist to do.  This is because
  		 * we don't have a convention for marking a rel as dummy except by
  		 * assigning a dummy path to it.
  		 */
  		set_dummy_rel_pathlist(rel);
  	}
  	else if (rte->inh)
  	{
  		/* It's an "append relation", process accordingly */
  		set_append_rel_size(root, rel, rti, rte);
  	}
  	else
  	{
  		switch (rel->rtekind)
  		{
  			case RTE_RELATION:
  				if (rte->relkind == RELKIND_FOREIGN_TABLE)
  				{
  					/* Foreign table */
  					set_foreign_size(root, rel, rte);
  				}
  				else if (rte->relkind == RELKIND_PARTITIONED_TABLE)
  				{
  					/*
  					 * A partitioned table without any partitions is marked as
  					 * a dummy rel.
  					 */
  					set_dummy_rel_pathlist(rel);
  				}
  				else if (rte->tablesample != NULL)
  				{
  					/* Sampled relation */
  					set_tablesample_rel_size(root, rel, rte);
  				}
  				else
  				{
  					/* Plain relation */
  					set_plain_rel_size(root, rel, rte);
  				}
  				break;
  			case RTE_SUBQUERY:
  
  				/*
  				 * Subqueries don't support making a choice between
  				 * parameterized and unparameterized paths, so just go ahead
  				 * and build their paths immediately.
  				 */
  				set_subquery_pathlist(root, rel, rti, rte);
  				break;
  			case RTE_FUNCTION:
  				set_function_size_estimates(root, rel);
  				break;
  			case RTE_TABLEFUNC:
  				set_tablefunc_size_estimates(root, rel);
  				break;
  			case RTE_VALUES:
  				set_values_size_estimates(root, rel);
  				break;
  			case RTE_CTE:
  
  				/*
  				 * CTEs don't support making a choice between parameterized
  				 * and unparameterized paths, so just go ahead and build their
  				 * paths immediately.
  				 */
  				if (rte->self_reference)
  					set_worktable_pathlist(root, rel, rte);
  				else
  					set_cte_pathlist(root, rel, rte);
  				break;
  			case RTE_NAMEDTUPLESTORE:
  				set_namedtuplestore_pathlist(root, rel, rte);
  				break;
  			default:
  				elog(ERROR, "unexpected rtekind: %d", (int) rel->rtekind);
  				break;
  		}
  	}
  
  	/*
  	 * We insist that all non-dummy rels have a nonzero rowcount estimate.
  	 */
  	Assert(rel->rows > 0 || IS_DUMMY_REL(rel));
  }
  
  /*
   * set_rel_pathlist
   *	  Build access paths for a base relation
   */
  static void
  set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
  				 Index rti, RangeTblEntry *rte)
  {
  	if (IS_DUMMY_REL(rel))
  	{
  		/* We already proved the relation empty, so nothing more to do */
  	}
  	else if (rte->inh)
  	{
  		/* It's an "append relation", process accordingly */
  		set_append_rel_pathlist(root, rel, rti, rte);
  	}
  	else
  	{
  		switch (rel->rtekind)
  		{
  			case RTE_RELATION:
  				if (rte->relkind == RELKIND_FOREIGN_TABLE)
  				{
  					/* Foreign table */
  					set_foreign_pathlist(root, rel, rte);
  				}
  				else if (rte->tablesample != NULL)
  				{
  					/* Sampled relation */
  					set_tablesample_rel_pathlist(root, rel, rte);
  				}
  				else
  				{
  					/* Plain relation */
  					set_plain_rel_pathlist(root, rel, rte);
  				}
  				break;
  			case RTE_SUBQUERY:
  				/* Subquery --- fully handled during set_rel_size */
  				break;
  			case RTE_FUNCTION:
  				/* RangeFunction */
  				set_function_pathlist(root, rel, rte);
  				break;
  			case RTE_TABLEFUNC:
  				/* Table Function */
  				set_tablefunc_pathlist(root, rel, rte);
  				break;
  			case RTE_VALUES:
  				/* Values list */
  				set_values_pathlist(root, rel, rte);
  				break;
  			case RTE_CTE:
  				/* CTE reference --- fully handled during set_rel_size */
  				break;
  			case RTE_NAMEDTUPLESTORE:
  				/* tuplestore reference --- fully handled during set_rel_size */
  				break;
  			default:
  				elog(ERROR, "unexpected rtekind: %d", (int) rel->rtekind);
  				break;
  		}
  	}
  
  	/*
  	 * If this is a baserel, consider gathering any partial paths we may have
  	 * created for it.  (If we tried to gather inheritance children, we could
  	 * end up with a very large number of gather nodes, each trying to grab
  	 * its own pool of workers, so don't do this for otherrels.  Instead,
  	 * we'll consider gathering partial paths for the parent appendrel.)
  	 */
  	if (rel->reloptkind == RELOPT_BASEREL)
  		generate_gather_paths(root, rel);
  
  	/*
  	 * Allow a plugin to editorialize on the set of Paths for this base
  	 * relation.  It could add new paths (such as CustomPaths) by calling
  	 * add_path(), or delete or modify paths added by the core code.
  	 */
  	if (set_rel_pathlist_hook)
  		(*set_rel_pathlist_hook) (root, rel, rti, rte);
  
  	/* Now find the cheapest of the paths for this rel */
  	set_cheapest(rel);
  
  #ifdef OPTIMIZER_DEBUG
  	debug_print_rel(root, rel);
  #endif
  }
  
  /*
   * set_plain_rel_size
   *	  Set size estimates for a plain relation (no subquery, no inheritance)
   */
  static void
  set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
  	/*
  	 * Test any partial indexes of rel for applicability.  We must do this
  	 * first since partial unique indexes can affect size estimates.
  	 */
  	check_index_predicates(root, rel);
  
  	/* Mark rel with estimated output rows, width, etc */
  	set_baserel_size_estimates(root, rel);
  }
  
  /*
   * If this relation could possibly be scanned from within a worker, then set
   * its consider_parallel flag.
   */
  static void
  set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
  						  RangeTblEntry *rte)
  {
  	/*
  	 * The flag has previously been initialized to false, so we can just
  	 * return if it becomes clear that we can't safely set it.
  	 */
  	Assert(!rel->consider_parallel);
  
  	/* Don't call this if parallelism is disallowed for the entire query. */
  	Assert(root->glob->parallelModeOK);
  
  	/* This should only be called for baserels and appendrel children. */
  	Assert(IS_SIMPLE_REL(rel));
  
  	/* Assorted checks based on rtekind. */
  	switch (rte->rtekind)
  	{
  		case RTE_RELATION:
  
  			/*
  			 * Currently, parallel workers can't access the leader's temporary
  			 * tables.  We could possibly relax this if the wrote all of its
  			 * local buffers at the start of the query and made no changes
  			 * thereafter (maybe we could allow hint bit changes), and if we
  			 * taught the workers to read them.  Writing a large number of
  			 * temporary buffers could be expensive, though, and we don't have
  			 * the rest of the necessary infrastructure right now anyway.  So
  			 * for now, bail out if we see a temporary table.
  			 */
  			if (get_rel_persistence(rte->relid) == RELPERSISTENCE_TEMP)
  				return;
  
  			/*
  			 * Table sampling can be pushed down to workers if the sample
  			 * function and its arguments are safe.
  			 */
  			if (rte->tablesample != NULL)
  			{
  				char		proparallel = func_parallel(rte->tablesample->tsmhandler);
  
  				if (proparallel != PROPARALLEL_SAFE)
  					return;
  				if (!is_parallel_safe(root, (Node *) rte->tablesample->args))
  					return;
  			}
  
  			/*
  			 * Ask FDWs whether they can support performing a ForeignScan
  			 * within a worker.  Most often, the answer will be no.  For
  			 * example, if the nature of the FDW is such that it opens a TCP
  			 * connection with a remote server, each parallel worker would end
  			 * up with a separate connection, and these connections might not
  			 * be appropriately coordinated between workers and the leader.
  			 */
  			if (rte->relkind == RELKIND_FOREIGN_TABLE)
  			{
  				Assert(rel->fdwroutine);
  				if (!rel->fdwroutine->IsForeignScanParallelSafe)
  					return;
  				if (!rel->fdwroutine->IsForeignScanParallelSafe(root, rel, rte))
  					return;
  			}
  
  			/*
  			 * There are additional considerations for appendrels, which we'll
  			 * deal with in set_append_rel_size and set_append_rel_pathlist.
  			 * For now, just set consider_parallel based on the rel's own
  			 * quals and targetlist.
  			 */
  			break;
  
  		case RTE_SUBQUERY:
  
  			/*
  			 * There's no intrinsic problem with scanning a subquery-in-FROM
  			 * (as distinct from a SubPlan or InitPlan) in a parallel worker.
  			 * If the subquery doesn't happen to have any parallel-safe paths,
  			 * then flagging it as consider_parallel won't change anything,
  			 * but that's true for plain tables, too.  We must set
  			 * consider_parallel based on the rel's own quals and targetlist,
  			 * so that if a subquery path is parallel-safe but the quals and
  			 * projection we're sticking onto it are not, we correctly mark
  			 * the SubqueryScanPath as not parallel-safe.  (Note that
  			 * set_subquery_pathlist() might push some of these quals down
  			 * into the subquery itself, but that doesn't change anything.)
  			 */
  			break;
  
  		case RTE_JOIN:
  			/* Shouldn't happen; we're only considering baserels here. */
  			Assert(false);
  			return;
  
  		case RTE_FUNCTION:
  			/* Check for parallel-restricted functions. */
  			if (!is_parallel_safe(root, (Node *) rte->functions))
  				return;
  			break;
  
  		case RTE_TABLEFUNC:
  			/* not parallel safe */
  			return;
  
  		case RTE_VALUES:
  			/* Check for parallel-restricted functions. */
  			if (!is_parallel_safe(root, (Node *) rte->values_lists))
  				return;
  			break;
  
  		case RTE_CTE:
  
  			/*
  			 * CTE tuplestores aren't shared among parallel workers, so we
  			 * force all CTE scans to happen in the leader.  Also, populating
  			 * the CTE would require executing a subplan that's not available
  			 * in the worker, might be parallel-restricted, and must get
  			 * executed only once.
  			 */
  			return;
  
  		case RTE_NAMEDTUPLESTORE:
  
  			/*
  			 * tuplestore cannot be shared, at least without more
  			 * infrastructure to support that.
  			 */
  			return;
  	}
  
  	/*
  	 * If there's anything in baserestrictinfo that's parallel-restricted, we
  	 * give up on parallelizing access to this relation.  We could consider
  	 * instead postponing application of the restricted quals until we're
  	 * above all the parallelism in the plan tree, but it's not clear that
  	 * that would be a win in very many cases, and it might be tricky to make
  	 * outer join clauses work correctly.  It would likely break equivalence
  	 * classes, too.
  	 */
  	if (!is_parallel_safe(root, (Node *) rel->baserestrictinfo))
  		return;
  
  	/*
  	 * Likewise, if the relation's outputs are not parallel-safe, give up.
  	 * (Usually, they're just Vars, but sometimes they're not.)
  	 */
  	if (!is_parallel_safe(root, (Node *) rel->reltarget->exprs))
  		return;
  
  	/* We have a winner. */
  	rel->consider_parallel = true;
  }
  
  /*
   * set_plain_rel_pathlist
   *	  Build access paths for a plain relation (no subquery, no inheritance)
   */
  static void
  set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
  	Relids		required_outer;
  
  	/*
  	 * We don't support pushing join clauses into the quals of a seqscan, but
  	 * it could still have required parameterization due to LATERAL refs in
  	 * its tlist.
  	 */
  	required_outer = rel->lateral_relids;
  
  	/* Consider sequential scan */
  	add_path(rel, create_seqscan_path(root, rel, required_outer, 0));
  
  	/* If appropriate, consider parallel sequential scan */
  	if (rel->consider_parallel && required_outer == NULL)
  		create_plain_partial_paths(root, rel);
  
  	/* Consider index scans */
  	create_index_paths(root, rel);
  
  	/* Consider TID scans */
  	create_tidscan_paths(root, rel);
  }
  
  /*
   * create_plain_partial_paths
   *	  Build partial access paths for parallel scan of a plain relation
   */
  static void
  create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel)
  {
  	int			parallel_workers;
  
  	parallel_workers = compute_parallel_worker(rel, rel->pages, -1);
  
  	/* If any limit was set to zero, the user doesn't want a parallel scan. */
  	if (parallel_workers <= 0)
  		return;
  
  	/* Add an unordered partial path based on a parallel sequential scan. */
  	add_partial_path(rel, create_seqscan_path(root, rel, NULL, parallel_workers));
  }
  
  /*
   * set_tablesample_rel_size
   *	  Set size estimates for a sampled relation
   */
  static void
  set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
  	TableSampleClause *tsc = rte->tablesample;
  	TsmRoutine *tsm;
  	BlockNumber pages;
  	double		tuples;
  
  	/*
  	 * Test any partial indexes of rel for applicability.  We must do this
  	 * first since partial unique indexes can affect size estimates.
  	 */
  	check_index_predicates(root, rel);
  
  	/*
  	 * Call the sampling method's estimation function to estimate the number
  	 * of pages it will read and the number of tuples it will return.  (Note:
  	 * we assume the function returns sane values.)
  	 */
  	tsm = GetTsmRoutine(tsc->tsmhandler);
  	tsm->SampleScanGetSampleSize(root, rel, tsc->args,
  								 &pages, &tuples);
  
  	/*
  	 * For the moment, because we will only consider a SampleScan path for the
  	 * rel, it's okay to just overwrite the pages and tuples estimates for the
  	 * whole relation.  If we ever consider multiple path types for sampled
  	 * rels, we'll need more complication.
  	 */
  	rel->pages = pages;
  	rel->tuples = tuples;
  
  	/* Mark rel with estimated output rows, width, etc */
  	set_baserel_size_estimates(root, rel);
  }
  
  /*
   * set_tablesample_rel_pathlist
   *	  Build access paths for a sampled relation
   */
  static void
  set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
  	Relids		required_outer;
  	Path	   *path;
  
  	/*
  	 * We don't support pushing join clauses into the quals of a samplescan,
  	 * but it could still have required parameterization due to LATERAL refs
  	 * in its tlist or TABLESAMPLE arguments.
  	 */
  	required_outer = rel->lateral_relids;
  
  	/* Consider sampled scan */
  	path = create_samplescan_path(root, rel, required_outer);
  
  	/*
  	 * If the sampling method does not support repeatable scans, we must avoid
  	 * plans that would scan the rel multiple times.  Ideally, we'd simply
  	 * avoid putting the rel on the inside of a nestloop join; but adding such
  	 * a consideration to the planner seems like a great deal of complication
  	 * to support an uncommon usage of second-rate sampling methods.  Instead,
  	 * if there is a risk that the query might perform an unsafe join, just
  	 * wrap the SampleScan in a Materialize node.  We can check for joins by
  	 * counting the membership of all_baserels (note that this correctly
  	 * counts inheritance trees as single rels).  If we're inside a subquery,
  	 * we can't easily check whether a join might occur in the outer query, so
  	 * just assume one is possible.
  	 *
  	 * GetTsmRoutine is relatively expensive compared to the other tests here,
  	 * so check repeatable_across_scans last, even though that's a bit odd.
  	 */
  	if ((root->query_level > 1 ||
  		 bms_membership(root->all_baserels) != BMS_SINGLETON) &&
  		!(GetTsmRoutine(rte->tablesample->tsmhandler)->repeatable_across_scans))
  	{
  		path = (Path *) create_material_path(rel, path);
  	}
  
  	add_path(rel, path);
  
  	/* For the moment, at least, there are no other paths to consider */
  }
  
  /*
   * set_foreign_size
   *		Set size estimates for a foreign table RTE
   */
  static void
  set_foreign_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
  	/* Mark rel with estimated output rows, width, etc */
  	set_foreign_size_estimates(root, rel);
  
  	/* Let FDW adjust the size estimates, if it can */
  	rel->fdwroutine->GetForeignRelSize(root, rel, rte->relid);
  
  	/* ... but do not let it set the rows estimate to zero */
  	rel->rows = clamp_row_est(rel->rows);
  }
  
  /*
   * set_foreign_pathlist
   *		Build access paths for a foreign table RTE
   */
  static void
  set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
  	/* Call the FDW's GetForeignPaths function to generate path(s) */
  	rel->fdwroutine->GetForeignPaths(root, rel, rte->relid);
  }
  
  /*
   * set_append_rel_size
   *	  Set size estimates for a simple "append relation"
   *
   * The passed-in rel and RTE represent the entire append relation.  The
   * relation's contents are computed by appending together the output of the
   * individual member relations.  Note that in the non-partitioned inheritance
   * case, the first member relation is actually the same table as is mentioned
   * in the parent RTE ... but it has a different RTE and RelOptInfo.  This is
   * a good thing because their outputs are not the same size.
   */
  static void
  set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
  					Index rti, RangeTblEntry *rte)
  {
  	int			parentRTindex = rti;
  	bool		has_live_children;
  	double		parent_rows;
  	double		parent_size;
  	double	   *parent_attrsizes;
  	int			nattrs;
  	ListCell   *l;
  
  	/* Guard against stack overflow due to overly deep inheritance tree. */
  	check_stack_depth();
  
  	Assert(IS_SIMPLE_REL(rel));
  
  	/*
  	 * Initialize to compute size estimates for whole append relation.
  	 *
  	 * We handle width estimates by weighting the widths of different child
  	 * rels proportionally to their number of rows.  This is sensible because
  	 * the use of width estimates is mainly to compute the total relation
  	 * "footprint" if we have to sort or hash it.  To do this, we sum the
  	 * total equivalent size (in "double" arithmetic) and then divide by the
  	 * total rowcount estimate.  This is done separately for the total rel
  	 * width and each attribute.
  	 *
  	 * Note: if you consider changing this logic, beware that child rels could
  	 * have zero rows and/or width, if they were excluded by constraints.
  	 */
  	has_live_children = false;
  	parent_rows = 0;
  	parent_size = 0;
  	nattrs = rel->max_attr - rel->min_attr + 1;
  	parent_attrsizes = (double *) palloc0(nattrs * sizeof(double));
  
  	foreach(l, root->append_rel_list)
  	{
  		AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
  		int			childRTindex;
  		RangeTblEntry *childRTE;
  		RelOptInfo *childrel;
  		List	   *childquals;
  		Index		cq_min_security;
  		bool		have_const_false_cq;
  		ListCell   *parentvars;
  		ListCell   *childvars;
  		ListCell   *lc;
  
  		/* append_rel_list contains all append rels; ignore others */
  		if (appinfo->parent_relid != parentRTindex)
  			continue;
  
  		childRTindex = appinfo->child_relid;
  		childRTE = root->simple_rte_array[childRTindex];
  
  		/*
  		 * The child rel's RelOptInfo was already created during
  		 * add_base_rels_to_query.
  		 */
  		childrel = find_base_rel(root, childRTindex);
  		Assert(childrel->reloptkind == RELOPT_OTHER_MEMBER_REL);
  
  		if (rel->part_scheme)
  		{
  			AttrNumber	attno;
  
  			/*
  			 * We need attr_needed data for building targetlist of a join
  			 * relation representing join between matching partitions for
  			 * partition-wise join. A given attribute of a child will be
  			 * needed in the same highest joinrel where the corresponding
  			 * attribute of parent is needed. Hence it suffices to use the
  			 * same Relids set for parent and child.
  			 */
  			for (attno = rel->min_attr; attno <= rel->max_attr; attno++)
  			{
  				int			index = attno - rel->min_attr;
  				Relids		attr_needed = rel->attr_needed[index];
  
  				/* System attributes do not need translation. */
  				if (attno <= 0)
  				{
  					Assert(rel->min_attr == childrel->min_attr);
  					childrel->attr_needed[index] = attr_needed;
  				}
  				else
  				{
  					Var		   *var = list_nth_node(Var,
  													appinfo->translated_vars,
  													attno - 1);
  					int			child_index;
  
  					/*
  					 * Ignore any column dropped from the parent.
  					 * Corresponding Var won't have any translation. It won't
  					 * have attr_needed information, since it can not be
  					 * referenced in the query.
  					 */
  					if (var == NULL)
  					{
  						Assert(attr_needed == NULL);
  						continue;
  					}
  
  					child_index = var->varattno - childrel->min_attr;
  					childrel->attr_needed[child_index] = attr_needed;
  				}
  			}
  		}
  
  		/*
  		 * Copy/Modify targetlist. Even if this child is deemed empty, we need
  		 * its targetlist in case it falls on nullable side in a child-join
  		 * because of partition-wise join.
  		 *
  		 * NB: the resulting childrel->reltarget->exprs may contain arbitrary
  		 * expressions, which otherwise would not occur in a rel's targetlist.
  		 * Code that might be looking at an appendrel child must cope with
  		 * such.  (Normally, a rel's targetlist would only include Vars and
  		 * PlaceHolderVars.)  XXX we do not bother to update the cost or width
  		 * fields of childrel->reltarget; not clear if that would be useful.
  		 */
  		childrel->reltarget->exprs = (List *)
  			adjust_appendrel_attrs(root,
  								   (Node *) rel->reltarget->exprs,
  								   1, &appinfo);
  
  		/*
  		 * We have to make child entries in the EquivalenceClass data
  		 * structures as well.  This is needed either if the parent
  		 * participates in some eclass joins (because we will want to consider
  		 * inner-indexscan joins on the individual children) or if the parent
  		 * has useful pathkeys (because we should try to build MergeAppend
  		 * paths that produce those sort orderings). Even if this child is
  		 * deemed dummy, it may fall on nullable side in a child-join, which
  		 * in turn may participate in a MergeAppend, where we will need the
  		 * EquivalenceClass data structures.
  		 */
  		if (rel->has_eclass_joins || has_useful_pathkeys(root, rel))
  			add_child_rel_equivalences(root, appinfo, rel, childrel);
  		childrel->has_eclass_joins = rel->has_eclass_joins;
  
  		/*
  		 * We have to copy the parent's quals to the child, with appropriate
  		 * substitution of variables.  However, only the baserestrictinfo
  		 * quals are needed before we can check for constraint exclusion; so
  		 * do that first and then check to see if we can disregard this child.
  		 *
  		 * The child rel's targetlist might contain non-Var expressions, which
  		 * means that substitution into the quals could produce opportunities
  		 * for const-simplification, and perhaps even pseudoconstant quals.
  		 * Therefore, transform each RestrictInfo separately to see if it
  		 * reduces to a constant or pseudoconstant.  (We must process them
  		 * separately to keep track of the security level of each qual.)
  		 */
  		childquals = NIL;
  		cq_min_security = UINT_MAX;
  		have_const_false_cq = false;
  		foreach(lc, rel->baserestrictinfo)
  		{
  			RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
  			Node	   *childqual;
  			ListCell   *lc2;
  
  			Assert(IsA(rinfo, RestrictInfo));
  			childqual = adjust_appendrel_attrs(root,
  											   (Node *) rinfo->clause,
  											   1, &appinfo);
  			childqual = eval_const_expressions(root, childqual);
  			/* check for flat-out constant */
  			if (childqual && IsA(childqual, Const))
  			{
  				if (((Const *) childqual)->constisnull ||
  					!DatumGetBool(((Const *) childqual)->constvalue))
  				{
  					/* Restriction reduces to constant FALSE or NULL */
  					have_const_false_cq = true;
  					break;
  				}
  				/* Restriction reduces to constant TRUE, so drop it */
  				continue;
  			}
  			/* might have gotten an AND clause, if so flatten it */
  			foreach(lc2, make_ands_implicit((Expr *) childqual))
  			{
  				Node	   *onecq = (Node *) lfirst(lc2);
  				bool		pseudoconstant;
  
  				/* check for pseudoconstant (no Vars or volatile functions) */
  				pseudoconstant =
  					!contain_vars_of_level(onecq, 0) &&
  					!contain_volatile_functions(onecq);
  				if (pseudoconstant)
  				{
  					/* tell createplan.c to check for gating quals */
  					root->hasPseudoConstantQuals = true;
  				}
  				/* reconstitute RestrictInfo with appropriate properties */
  				childquals = lappend(childquals,
  									 make_restrictinfo((Expr *) onecq,
  													   rinfo->is_pushed_down,
  													   rinfo->outerjoin_delayed,
  													   pseudoconstant,
  													   rinfo->security_level,
  													   NULL, NULL, NULL));
  				/* track minimum security level among child quals */
  				cq_min_security = Min(cq_min_security, rinfo->security_level);
  			}
  		}
  
  		/*
  		 * In addition to the quals inherited from the parent, we might have
  		 * securityQuals associated with this particular child node.
  		 * (Currently this can only happen in appendrels originating from
  		 * UNION ALL; inheritance child tables don't have their own
  		 * securityQuals, see expand_inherited_rtentry().)	Pull any such
  		 * securityQuals up into the baserestrictinfo for the child.  This is
  		 * similar to process_security_barrier_quals() for the parent rel,
  		 * except that we can't make any general deductions from such quals,
  		 * since they don't hold for the whole appendrel.
  		 */
  		if (childRTE->securityQuals)
  		{
  			Index		security_level = 0;
  
  			foreach(lc, childRTE->securityQuals)
  			{
  				List	   *qualset = (List *) lfirst(lc);
  				ListCell   *lc2;
  
  				foreach(lc2, qualset)
  				{
  					Expr	   *qual = (Expr *) lfirst(lc2);
  
  					/* not likely that we'd see constants here, so no check */
  					childquals = lappend(childquals,
  										 make_restrictinfo(qual,
  														   true, false, false,
  														   security_level,
  														   NULL, NULL, NULL));
  					cq_min_security = Min(cq_min_security, security_level);
  				}
  				security_level++;
  			}
  			Assert(security_level <= root->qual_security_level);
  		}
  
  		/*
  		 * OK, we've got all the baserestrictinfo quals for this child.
  		 */
  		childrel->baserestrictinfo = childquals;
  		childrel->baserestrict_min_security = cq_min_security;
  
  		if (have_const_false_cq)
  		{
  			/*
  			 * Some restriction clause reduced to constant FALSE or NULL after
  			 * substitution, so this child need not be scanned.
  			 */
  			set_dummy_rel_pathlist(childrel);
  			continue;
  		}
  
  		if (relation_excluded_by_constraints(root, childrel, childRTE))
  		{
  			/*
  			 * This child need not be scanned, so we can omit it from the
  			 * appendrel.
  			 */
  			set_dummy_rel_pathlist(childrel);
  			continue;
  		}
  
  		/* CE failed, so finish copying/modifying join quals. */
  		childrel->joininfo = (List *)
  			adjust_appendrel_attrs(root,
  								   (Node *) rel->joininfo,
  								   1, &appinfo);
  
  		/*
  		 * If parallelism is allowable for this query in general, see whether
  		 * it's allowable for this childrel in particular.  But if we've
  		 * already decided the appendrel is not parallel-safe as a whole,
  		 * there's no point in considering parallelism for this child.  For
  		 * consistency, do this before calling set_rel_size() for the child.
  		 */
  		if (root->glob->parallelModeOK && rel->consider_parallel)
  			set_rel_consider_parallel(root, childrel, childRTE);
  
  		/*
  		 * Compute the child's size.
  		 */
  		set_rel_size(root, childrel, childRTindex, childRTE);
  
  		/*
  		 * It is possible that constraint exclusion detected a contradiction
  		 * within a child subquery, even though we didn't prove one above. If
  		 * so, we can skip this child.
  		 */
  		if (IS_DUMMY_REL(childrel))
  			continue;
  
  		/* We have at least one live child. */
  		has_live_children = true;
  
  		/*
  		 * If any live child is not parallel-safe, treat the whole appendrel
  		 * as not parallel-safe.  In future we might be able to generate plans
  		 * in which some children are farmed out to workers while others are
  		 * not; but we don't have that today, so it's a waste to consider
  		 * partial paths anywhere in the appendrel unless it's all safe.
  		 * (Child rels visited before this one will be unmarked in
  		 * set_append_rel_pathlist().)
  		 */
  		if (!childrel->consider_parallel)
  			rel->consider_parallel = false;
  
  		/*
  		 * Accumulate size information from each live child.
  		 */
  		Assert(childrel->rows > 0);
  
  		parent_rows += childrel->rows;
  		parent_size += childrel->reltarget->width * childrel->rows;
  
  		/*
  		 * Accumulate per-column estimates too.  We need not do anything for
  		 * PlaceHolderVars in the parent list.  If child expression isn't a
  		 * Var, or we didn't record a width estimate for it, we have to fall
  		 * back on a datatype-based estimate.
  		 *
  		 * By construction, child's targetlist is 1-to-1 with parent's.
  		 */
  		forboth(parentvars, rel->reltarget->exprs,
  				childvars, childrel->reltarget->exprs)
  		{
  			Var		   *parentvar = (Var *) lfirst(parentvars);
  			Node	   *childvar = (Node *) lfirst(childvars);
  
  			if (IsA(parentvar, Var))
  			{
  				int			pndx = parentvar->varattno - rel->min_attr;
  				int32		child_width = 0;
  
  				if (IsA(childvar, Var) &&
  					((Var *) childvar)->varno == childrel->relid)
  				{
  					int			cndx = ((Var *) childvar)->varattno - childrel->min_attr;
  
  					child_width = childrel->attr_widths[cndx];
  				}
  				if (child_width <= 0)
  					child_width = get_typavgwidth(exprType(childvar),
  												  exprTypmod(childvar));
  				Assert(child_width > 0);
  				parent_attrsizes[pndx] += child_width * childrel->rows;
  			}
  		}
  	}
  
  	if (has_live_children)
  	{
  		/*
  		 * Save the finished size estimates.
  		 */
  		int			i;
  
  		Assert(parent_rows > 0);
  		rel->rows = parent_rows;
  		rel->reltarget->width = rint(parent_size / parent_rows);
  		for (i = 0; i < nattrs; i++)
  			rel->attr_widths[i] = rint(parent_attrsizes[i] / parent_rows);
  
  		/*
  		 * Set "raw tuples" count equal to "rows" for the appendrel; needed
  		 * because some places assume rel->tuples is valid for any baserel.
  		 */
  		rel->tuples = parent_rows;
  	}
  	else
  	{
  		/*
  		 * All children were excluded by constraints, so mark the whole
  		 * appendrel dummy.  We must do this in this phase so that the rel's
  		 * dummy-ness is visible when we generate paths for other rels.
  		 */
  		set_dummy_rel_pathlist(rel);
  	}
  
  	pfree(parent_attrsizes);
  }
  
  /*
   * set_append_rel_pathlist
   *	  Build access paths for an "append relation"
   */
  static void
  set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
  						Index rti, RangeTblEntry *rte)
  {
  	int			parentRTindex = rti;
  	List	   *live_childrels = NIL;
  	ListCell   *l;
  
  	/*
  	 * Generate access paths for each member relation, and remember the
  	 * non-dummy children.
  	 */
  	foreach(l, root->append_rel_list)
  	{
  		AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
  		int			childRTindex;
  		RangeTblEntry *childRTE;
  		RelOptInfo *childrel;
  
  		/* append_rel_list contains all append rels; ignore others */
  		if (appinfo->parent_relid != parentRTindex)
  			continue;
  
  		/* Re-locate the child RTE and RelOptInfo */
  		childRTindex = appinfo->child_relid;
  		childRTE = root->simple_rte_array[childRTindex];
  		childrel = root->simple_rel_array[childRTindex];
  
  		/*
  		 * If set_append_rel_size() decided the parent appendrel was
  		 * parallel-unsafe at some point after visiting this child rel, we
  		 * need to propagate the unsafety marking down to the child, so that
  		 * we don't generate useless partial paths for it.
  		 */
  		if (!rel->consider_parallel)
  			childrel->consider_parallel = false;
  
  		/*
  		 * Compute the child's access paths.
  		 */
  		set_rel_pathlist(root, childrel, childRTindex, childRTE);
  
  		/*
  		 * If child is dummy, ignore it.
  		 */
  		if (IS_DUMMY_REL(childrel))
  			continue;
  
  		/*
  		 * Child is live, so add it to the live_childrels list for use below.
  		 */
  		live_childrels = lappend(live_childrels, childrel);
  	}
  
  	/* Add paths to the append relation. */
  	add_paths_to_append_rel(root, rel, live_childrels);
  }
  
  
  /*
   * add_paths_to_append_rel
   *		Generate paths for the given append relation given the set of non-dummy
   *		child rels.
   *
   * The function collects all parameterizations and orderings supported by the
   * non-dummy children. For every such parameterization or ordering, it creates
   * an append path collecting one path from each non-dummy child with given
   * parameterization or ordering. Similarly it collects partial paths from
   * non-dummy children to create partial append paths.
   */
  static void
  add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
  						List *live_childrels)
  {
  	List	   *subpaths = NIL;
  	bool		subpaths_valid = true;
  	List	   *partial_subpaths = NIL;
  	bool		partial_subpaths_valid = true;
  	List	   *all_child_pathkeys = NIL;
  	List	   *all_child_outers = NIL;
  	ListCell   *l;
  	List	   *partitioned_rels = NIL;
  	RangeTblEntry *rte;
  	bool		build_partitioned_rels = false;
  
  	if (IS_SIMPLE_REL(rel))
  	{
  		/*
  		 * A root partition will already have a PartitionedChildRelInfo, and a
  		 * non-root partitioned table doesn't need one, because its Append
  		 * paths will get flattened into the parent anyway.  For a subquery
  		 * RTE, no PartitionedChildRelInfo exists; we collect all
  		 * partitioned_rels associated with any child.  (This assumes that we
  		 * don't need to look through multiple levels of subquery RTEs; if we
  		 * ever do, we could create a PartitionedChildRelInfo with the
  		 * accumulated list of partitioned_rels which would then be found when
  		 * populated our parent rel with paths.  For the present, that appears
  		 * to be unnecessary.)
  		 */
  		rte = planner_rt_fetch(rel->relid, root);
  		switch (rte->rtekind)
  		{
  			case RTE_RELATION:
  				if (rte->relkind == RELKIND_PARTITIONED_TABLE)
  					partitioned_rels =
  						get_partitioned_child_rels(root, rel->relid);
  				break;
  			case RTE_SUBQUERY:
  				build_partitioned_rels = true;
  				break;
  			default:
  				elog(ERROR, "unexpected rtekind: %d", (int) rte->rtekind);
  		}
  	}
  	else if (rel->reloptkind == RELOPT_JOINREL && rel->part_scheme)
  	{
  		/*
  		 * Associate PartitionedChildRelInfo of the root partitioned tables
  		 * being joined with the root partitioned join (indicated by
  		 * RELOPT_JOINREL).
  		 */
  		partitioned_rels = get_partitioned_child_rels_for_join(root,
  															   rel->relids);
  	}
  
  	/*
  	 * For every non-dummy child, remember the cheapest path.  Also, identify
  	 * all pathkeys (orderings) and parameterizations (required_outer sets)
  	 * available for the non-dummy member relations.
  	 */
  	foreach(l, live_childrels)
  	{
  		RelOptInfo *childrel = lfirst(l);
  		ListCell   *lcp;
  
  		/*
  		 * If we need to build partitioned_rels, accumulate the partitioned
  		 * rels for this child.
  		 */
  		if (build_partitioned_rels)
  		{
  			List	   *cprels;
  
  			cprels = get_partitioned_child_rels(root, childrel->relid);
  			partitioned_rels = list_concat(partitioned_rels,
  										   list_copy(cprels));
  		}
  
  		/*
  		 * If child has an unparameterized cheapest-total path, add that to
  		 * the unparameterized Append path we are constructing for the parent.
  		 * If not, there's no workable unparameterized path.
  		 */
  		if (childrel->cheapest_total_path->param_info == NULL)
  			subpaths = accumulate_append_subpath(subpaths,
  												 childrel->cheapest_total_path);
  		else
  			subpaths_valid = false;
  
  		/* Same idea, but for a partial plan. */
  		if (childrel->partial_pathlist != NIL)
  			partial_subpaths = accumulate_append_subpath(partial_subpaths,
  														 linitial(childrel->partial_pathlist));
  		else
  			partial_subpaths_valid = false;
  
  		/*
  		 * Collect lists of all the available path orderings and
  		 * parameterizations for all the children.  We use these as a
  		 * heuristic to indicate which sort orderings and parameterizations we
  		 * should build Append and MergeAppend paths for.
  		 */
  		foreach(lcp, childrel->pathlist)
  		{
  			Path	   *childpath = (Path *) lfirst(lcp);
  			List	   *childkeys = childpath->pathkeys;
  			Relids		childouter = PATH_REQ_OUTER(childpath);
  
  			/* Unsorted paths don't contribute to pathkey list */
  			if (childkeys != NIL)
  			{
  				ListCell   *lpk;
  				bool		found = false;
  
  				/* Have we already seen this ordering? */
  				foreach(lpk, all_child_pathkeys)
  				{
  					List	   *existing_pathkeys = (List *) lfirst(lpk);
  
  					if (compare_pathkeys(existing_pathkeys,
  										 childkeys) == PATHKEYS_EQUAL)
  					{
  						found = true;
  						break;
  					}
  				}
  				if (!found)
  				{
  					/* No, so add it to all_child_pathkeys */
  					all_child_pathkeys = lappend(all_child_pathkeys,
  												 childkeys);
  				}
  			}
  
  			/* Unparameterized paths don't contribute to param-set list */
  			if (childouter)
  			{
  				ListCell   *lco;
  				bool		found = false;
  
  				/* Have we already seen this param set? */
  				foreach(lco, all_child_outers)
  				{
  					Relids		existing_outers = (Relids) lfirst(lco);
  
  					if (bms_equal(existing_outers, childouter))
  					{
  						found = true;
  						break;
  					}
  				}
  				if (!found)
  				{
  					/* No, so add it to all_child_outers */
  					all_child_outers = lappend(all_child_outers,
  											   childouter);
  				}
  			}
  		}
  	}
  
  	/*
  	 * If we found unparameterized paths for all children, build an unordered,
  	 * unparameterized Append path for the rel.  (Note: this is correct even
  	 * if we have zero or one live subpath due to constraint exclusion.)
  	 */
  	if (subpaths_valid)
  		add_path(rel, (Path *) create_append_path(rel, subpaths, NULL, 0,
  												  partitioned_rels));
  
  	/*
  	 * Consider an append of partial unordered, unparameterized partial paths.
  	 */
  	if (partial_subpaths_valid)
  	{
  		AppendPath *appendpath;
  		ListCell   *lc;
  		int			parallel_workers = 0;
  
  		/*
  		 * Decide on the number of workers to request for this append path.
  		 * For now, we just use the maximum value from among the members.  It
  		 * might be useful to use a higher number if the Append node were
  		 * smart enough to spread out the workers, but it currently isn't.
  		 */
  		foreach(lc, partial_subpaths)
  		{
  			Path	   *path = lfirst(lc);
  
  			parallel_workers = Max(parallel_workers, path->parallel_workers);
  		}
  		Assert(parallel_workers > 0);
  
  		/* Generate a partial append path. */
  		appendpath = create_append_path(rel, partial_subpaths, NULL,
  										parallel_workers, partitioned_rels);
  		add_partial_path(rel, (Path *) appendpath);
  	}
  
  	/*
  	 * Also build unparameterized MergeAppend paths based on the collected
  	 * list of child pathkeys.
  	 */
  	if (subpaths_valid)
  		generate_mergeappend_paths(root, rel, live_childrels,
  								   all_child_pathkeys,
  								   partitioned_rels);
  
  	/*
  	 * Build Append paths for each parameterization seen among the child rels.
  	 * (This may look pretty expensive, but in most cases of practical
  	 * interest, the child rels will expose mostly the same parameterizations,
  	 * so that not that many cases actually get considered here.)
  	 *
  	 * The Append node itself cannot enforce quals, so all qual checking must
  	 * be done in the child paths.  This means that to have a parameterized
  	 * Append path, we must have the exact same parameterization for each
  	 * child path; otherwise some children might be failing to check the
  	 * moved-down quals.  To make them match up, we can try to increase the
  	 * parameterization of lesser-parameterized paths.
  	 */
  	foreach(l, all_child_outers)
  	{
  		Relids		required_outer = (Relids) lfirst(l);
  		ListCell   *lcr;
  
  		/* Select the child paths for an Append with this parameterization */
  		subpaths = NIL;
  		subpaths_valid = true;
  		foreach(lcr, live_childrels)
  		{
  			RelOptInfo *childrel = (RelOptInfo *) lfirst(lcr);
  			Path	   *subpath;
  
  			subpath = get_cheapest_parameterized_child_path(root,
  															childrel,
  															required_outer);
  			if (subpath == NULL)
  			{
  				/* failed to make a suitable path for this child */
  				subpaths_valid = false;
  				break;
  			}
  			subpaths = accumulate_append_subpath(subpaths, subpath);
  		}
  
  		if (subpaths_valid)
  			add_path(rel, (Path *)
  					 create_append_path(rel, subpaths, required_outer, 0,
  										partitioned_rels));
  	}
  }
  
  /*
   * generate_mergeappend_paths
   *		Generate MergeAppend paths for an append relation
   *
   * Generate a path for each ordering (pathkey list) appearing in
   * all_child_pathkeys.
   *
   * We consider both cheapest-startup and cheapest-total cases, ie, for each
   * interesting ordering, collect all the cheapest startup subpaths and all the
   * cheapest total paths, and build a MergeAppend path for each case.
   *
   * We don't currently generate any parameterized MergeAppend paths.  While
   * it would not take much more code here to do so, it's very unclear that it
   * is worth the planning cycles to investigate such paths: there's little
   * use for an ordered path on the inside of a nestloop.  In fact, it's likely
   * that the current coding of add_path would reject such paths out of hand,
   * because add_path gives no credit for sort ordering of parameterized paths,
   * and a parameterized MergeAppend is going to be more expensive than the
   * corresponding parameterized Append path.  If we ever try harder to support
   * parameterized mergejoin plans, it might be worth adding support for
   * parameterized MergeAppends to feed such joins.  (See notes in
   * optimizer/README for why that might not ever happen, though.)
   */
  static void
  generate_mergeappend_paths(PlannerInfo *root, RelOptInfo *rel,
  						   List *live_childrels,
  						   List *all_child_pathkeys,
  						   List *partitioned_rels)
  {
  	ListCell   *lcp;
  
  	foreach(lcp, all_child_pathkeys)
  	{
  		List	   *pathkeys = (List *) lfirst(lcp);
  		List	   *startup_subpaths = NIL;
  		List	   *total_subpaths = NIL;
  		bool		startup_neq_total = false;
  		ListCell   *lcr;
  
  		/* Select the child paths for this ordering... */
  		foreach(lcr, live_childrels)
  		{
  			RelOptInfo *childrel = (RelOptInfo *) lfirst(lcr);
  			Path	   *cheapest_startup,
  					   *cheapest_total;
  
  			/* Locate the right paths, if they are available. */
  			cheapest_startup =
  				get_cheapest_path_for_pathkeys(childrel->pathlist,
  											   pathkeys,
  											   NULL,
  											   STARTUP_COST,
  											   false);
  			cheapest_total =
  				get_cheapest_path_for_pathkeys(childrel->pathlist,
  											   pathkeys,
  											   NULL,
  											   TOTAL_COST,
  											   false);
  
  			/*
  			 * If we can't find any paths with the right order just use the
  			 * cheapest-total path; we'll have to sort it later.
  			 */
  			if (cheapest_startup == NULL || cheapest_total == NULL)
  			{
  				cheapest_startup = cheapest_total =
  					childrel->cheapest_total_path;
  				/* Assert we do have an unparameterized path for this child */
  				Assert(cheapest_total->param_info == NULL);
  			}
  
  			/*
  			 * Notice whether we actually have different paths for the
  			 * "cheapest" and "total" cases; frequently there will be no point
  			 * in two create_merge_append_path() calls.
  			 */
  			if (cheapest_startup != cheapest_total)
  				startup_neq_total = true;
  
  			startup_subpaths =
  				accumulate_append_subpath(startup_subpaths, cheapest_startup);
  			total_subpaths =
  				accumulate_append_subpath(total_subpaths, cheapest_total);
  		}
  
  		/* ... and build the MergeAppend paths */
  		add_path(rel, (Path *) create_merge_append_path(root,
  														rel,
  														startup_subpaths,
  														pathkeys,
  														NULL,
  														partitioned_rels));
  		if (startup_neq_total)
  			add_path(rel, (Path *) create_merge_append_path(root,
  															rel,
  															total_subpaths,
  															pathkeys,
  															NULL,
  															partitioned_rels));
  	}
  }
  
  /*
   * get_cheapest_parameterized_child_path
   *		Get cheapest path for this relation that has exactly the requested
   *		parameterization.
   *
   * Returns NULL if unable to create such a path.
   */
  static Path *
  get_cheapest_parameterized_child_path(PlannerInfo *root, RelOptInfo *rel,
  									  Relids required_outer)
  {
  	Path	   *cheapest;
  	ListCell   *lc;
  
  	/*
  	 * Look up the cheapest existing path with no more than the needed
  	 * parameterization.  If it has exactly the needed parameterization, we're
  	 * done.
  	 */
  	cheapest = get_cheapest_path_for_pathkeys(rel->pathlist,
  											  NIL,
  											  required_outer,
  											  TOTAL_COST,
  											  false);
  	Assert(cheapest != NULL);
  	if (bms_equal(PATH_REQ_OUTER(cheapest), required_outer))
  		return cheapest;
  
  	/*
  	 * Otherwise, we can "reparameterize" an existing path to match the given
  	 * parameterization, which effectively means pushing down additional
  	 * joinquals to be checked within the path's scan.  However, some existing
  	 * paths might check the available joinquals already while others don't;
  	 * therefore, it's not clear which existing path will be cheapest after
  	 * reparameterization.  We have to go through them all and find out.
  	 */
  	cheapest = NULL;
  	foreach(lc, rel->pathlist)
  	{
  		Path	   *path = (Path *) lfirst(lc);
  
  		/* Can't use it if it needs more than requested parameterization */
  		if (!bms_is_subset(PATH_REQ_OUTER(path), required_outer))
  			continue;
  
  		/*
  		 * Reparameterization can only increase the path's cost, so if it's
  		 * already more expensive than the current cheapest, forget it.
  		 */
  		if (cheapest != NULL &&
  			compare_path_costs(cheapest, path, TOTAL_COST) <= 0)
  			continue;
  
  		/* Reparameterize if needed, then recheck cost */
  		if (!bms_equal(PATH_REQ_OUTER(path), required_outer))
  		{
  			path = reparameterize_path(root, path, required_outer, 1.0);
  			if (path == NULL)
  				continue;		/* failed to reparameterize this one */
  			Assert(bms_equal(PATH_REQ_OUTER(path), required_outer));
  
  			if (cheapest != NULL &&
  				compare_path_costs(cheapest, path, TOTAL_COST) <= 0)
  				continue;
  		}
  
  		/* We have a new best path */
  		cheapest = path;
  	}
  
  	/* Return the best path, or NULL if we found no suitable candidate */
  	return cheapest;
  }
  
  /*
   * accumulate_append_subpath
   *		Add a subpath to the list being built for an Append or MergeAppend
   *
   * It's possible that the child is itself an Append or MergeAppend path, in
   * which case we can "cut out the middleman" and just add its child paths to
   * our own list.  (We don't try to do this earlier because we need to apply
   * both levels of transformation to the quals.)
   *
   * Note that if we omit a child MergeAppend in this way, we are effectively
   * omitting a sort step, which seems fine: if the parent is to be an Append,
   * its result would be unsorted anyway, while if the parent is to be a
   * MergeAppend, there's no point in a separate sort on a child.
   */
  static List *
  accumulate_append_subpath(List *subpaths, Path *path)
  {
  	if (IsA(path, AppendPath))
  	{
  		AppendPath *apath = (AppendPath *) path;
  
  		/* list_copy is important here to avoid sharing list substructure */
  		return list_concat(subpaths, list_copy(apath->subpaths));
  	}
  	else if (IsA(path, MergeAppendPath))
  	{
  		MergeAppendPath *mpath = (MergeAppendPath *) path;
  
  		/* list_copy is important here to avoid sharing list substructure */
  		return list_concat(subpaths, list_copy(mpath->subpaths));
  	}
  	else
  		return lappend(subpaths, path);
  }
  
  /*
   * set_dummy_rel_pathlist
   *	  Build a dummy path for a relation that's been excluded by constraints
   *
   * Rather than inventing a special "dummy" path type, we represent this as an
   * AppendPath with no members (see also IS_DUMMY_PATH/IS_DUMMY_REL macros).
   *
   * This is exported because inheritance_planner() has need for it.
   */
  void
  set_dummy_rel_pathlist(RelOptInfo *rel)
  {
  	/* Set dummy size estimates --- we leave attr_widths[] as zeroes */
  	rel->rows = 0;
  	rel->reltarget->width = 0;
  
  	/* Discard any pre-existing paths; no further need for them */
  	rel->pathlist = NIL;
  	rel->partial_pathlist = NIL;
  
  	add_path(rel, (Path *) create_append_path(rel, NIL, NULL, 0, NIL));
  
  	/*
  	 * We set the cheapest path immediately, to ensure that IS_DUMMY_REL()
  	 * will recognize the relation as dummy if anyone asks.  This is redundant
  	 * when we're called from set_rel_size(), but not when called from
  	 * elsewhere, and doing it twice is harmless anyway.
  	 */
  	set_cheapest(rel);
  }
  
  /* quick-and-dirty test to see if any joining is needed */
  static bool
  has_multiple_baserels(PlannerInfo *root)
  {
  	int			num_base_rels = 0;
  	Index		rti;
  
  	for (rti = 1; rti < root->simple_rel_array_size; rti++)
  	{
  		RelOptInfo *brel = root->simple_rel_array[rti];
  
  		if (brel == NULL)
  			continue;
  
  		/* ignore RTEs that are "other rels" */
  		if (brel->reloptkind == RELOPT_BASEREL)
  			if (++num_base_rels > 1)
  				return true;
  	}
  	return false;
  }
  
  /*
   * set_subquery_pathlist
   *		Generate SubqueryScan access paths for a subquery RTE
   *
   * We don't currently support generating parameterized paths for subqueries
   * by pushing join clauses down into them; it seems too expensive to re-plan
   * the subquery multiple times to consider different alternatives.
   * (XXX that could stand to be reconsidered, now that we use Paths.)
   * So the paths made here will be parameterized if the subquery contains
   * LATERAL references, otherwise not.  As long as that's true, there's no need
   * for a separate set_subquery_size phase: just make the paths right away.
   */
  static void
  set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
  					  Index rti, RangeTblEntry *rte)
  {
  	Query	   *parse = root->parse;
  	Query	   *subquery = rte->subquery;
  	Relids		required_outer;
  	pushdown_safety_info safetyInfo;
  	double		tuple_fraction;
  	RelOptInfo *sub_final_rel;
  	ListCell   *lc;
  
  	/*
  	 * Must copy the Query so that planning doesn't mess up the RTE contents
  	 * (really really need to fix the planner to not scribble on its input,
  	 * someday ... but see remove_unused_subquery_outputs to start with).
  	 */
  	subquery = copyObject(subquery);
  
  	/*
  	 * If it's a LATERAL subquery, it might contain some Vars of the current
  	 * query level, requiring it to be treated as parameterized, even though
  	 * we don't support pushing down join quals into subqueries.
  	 */
  	required_outer = rel->lateral_relids;
  
  	/*
  	 * Zero out result area for subquery_is_pushdown_safe, so that it can set
  	 * flags as needed while recursing.  In particular, we need a workspace
  	 * for keeping track of unsafe-to-reference columns.  unsafeColumns[i]
  	 * will be set true if we find that output column i of the subquery is
  	 * unsafe to use in a pushed-down qual.
  	 */
  	memset(&safetyInfo, 0, sizeof(safetyInfo));
  	safetyInfo.unsafeColumns = (bool *)
  		palloc0((list_length(subquery->targetList) + 1) * sizeof(bool));
  
  	/*
  	 * If the subquery has the "security_barrier" flag, it means the subquery
  	 * originated from a view that must enforce row level security.  Then we
  	 * must not push down quals that contain leaky functions.  (Ideally this
  	 * would be checked inside subquery_is_pushdown_safe, but since we don't
  	 * currently pass the RTE to that function, we must do it here.)
  	 */
  	safetyInfo.unsafeLeaky = rte->security_barrier;
  
  	/*
  	 * If there are any restriction clauses that have been attached to the
  	 * subquery relation, consider pushing them down to become WHERE or HAVING
  	 * quals of the subquery itself.  This transformation is useful because it
  	 * may allow us to generate a better plan for the subquery than evaluating
  	 * all the subquery output rows and then filtering them.
  	 *
  	 * There are several cases where we cannot push down clauses. Restrictions
  	 * involving the subquery are checked by subquery_is_pushdown_safe().
  	 * Restrictions on individual clauses are checked by
  	 * qual_is_pushdown_safe().  Also, we don't want to push down
  	 * pseudoconstant clauses; better to have the gating node above the
  	 * subquery.
  	 *
  	 * Non-pushed-down clauses will get evaluated as qpquals of the
  	 * SubqueryScan node.
  	 *
  	 * XXX Are there any cases where we want to make a policy decision not to
  	 * push down a pushable qual, because it'd result in a worse plan?
  	 */
  	if (rel->baserestrictinfo != NIL &&
  		subquery_is_pushdown_safe(subquery, subquery, &safetyInfo))
  	{
  		/* OK to consider pushing down individual quals */
  		List	   *upperrestrictlist = NIL;
  		ListCell   *l;
  
  		foreach(l, rel->baserestrictinfo)
  		{
  			RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
  			Node	   *clause = (Node *) rinfo->clause;
  
  			if (!rinfo->pseudoconstant &&
  				qual_is_pushdown_safe(subquery, rti, clause, &safetyInfo))
  			{
  				/* Push it down */
  				subquery_push_qual(subquery, rte, rti, clause);
  			}
  			else
  			{
  				/* Keep it in the upper query */
  				upperrestrictlist = lappend(upperrestrictlist, rinfo);
  			}
  		}
  		rel->baserestrictinfo = upperrestrictlist;
  		/* We don't bother recomputing baserestrict_min_security */
  	}
  
  	pfree(safetyInfo.unsafeColumns);
  
  	/*
  	 * The upper query might not use all the subquery's output columns; if
  	 * not, we can simplify.
  	 */
  	remove_unused_subquery_outputs(subquery, rel);
  
  	/*
  	 * We can safely pass the outer tuple_fraction down to the subquery if the
  	 * outer level has no joining, aggregation, or sorting to do. Otherwise
  	 * we'd better tell the subquery to plan for full retrieval. (XXX This
  	 * could probably be made more intelligent ...)
  	 */
  	if (parse->hasAggs ||
  		parse->groupClause ||
  		parse->groupingSets ||
  		parse->havingQual ||
  		parse->distinctClause ||
  		parse->sortClause ||
  		has_multiple_baserels(root))
  		tuple_fraction = 0.0;	/* default case */
  	else
  		tuple_fraction = root->tuple_fraction;
  
  	/* plan_params should not be in use in current query level */
  	Assert(root->plan_params == NIL);
  
  	/* Generate a subroot and Paths for the subquery */
  	rel->subroot = subquery_planner(root->glob, subquery,
  									root,
  									false, tuple_fraction);
  
  	/* Isolate the params needed by this specific subplan */
  	rel->subplan_params = root->plan_params;
  	root->plan_params = NIL;
  
  	/*
  	 * It's possible that constraint exclusion proved the subquery empty. If
  	 * so, it's desirable to produce an unadorned dummy path so that we will
  	 * recognize appropriate optimizations at this query level.
  	 */
  	sub_final_rel = fetch_upper_rel(rel->subroot, UPPERREL_FINAL, NULL);
  
  	if (IS_DUMMY_REL(sub_final_rel))
  	{
  		set_dummy_rel_pathlist(rel);
  		return;
  	}
  
  	/*
  	 * Mark rel with estimated output rows, width, etc.  Note that we have to
  	 * do this before generating outer-query paths, else cost_subqueryscan is
  	 * not happy.
  	 */
  	set_subquery_size_estimates(root, rel);
  
  	/*
  	 * For each Path that subquery_planner produced, make a SubqueryScanPath
  	 * in the outer query.
  	 */
  	foreach(lc, sub_final_rel->pathlist)
  	{
  		Path	   *subpath = (Path *) lfirst(lc);
  		List	   *pathkeys;
  
  		/* Convert subpath's pathkeys to outer representation */
  		pathkeys = convert_subquery_pathkeys(root,
  											 rel,
  											 subpath->pathkeys,
  											 make_tlist_from_pathtarget(subpath->pathtarget));
  
  		/* Generate outer path using this subpath */
  		add_path(rel, (Path *)
  				 create_subqueryscan_path(root, rel, subpath,
  										  pathkeys, required_outer));
  	}
  }
  
  /*
   * set_function_pathlist
   *		Build the (single) access path for a function RTE
   */
  static void
  set_function_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
  	Relids		required_outer;
  	List	   *pathkeys = NIL;
  
  	/*
  	 * We don't support pushing join clauses into the quals of a function
  	 * scan, but it could still have required parameterization due to LATERAL
  	 * refs in the function expression.
  	 */
  	required_outer = rel->lateral_relids;
  
  	/*
  	 * The result is considered unordered unless ORDINALITY was used, in which
  	 * case it is ordered by the ordinal column (the last one).  See if we
  	 * care, by checking for uses of that Var in equivalence classes.
  	 */
  	if (rte->funcordinality)
  	{
  		AttrNumber	ordattno = rel->max_attr;
  		Var		   *var = NULL;
  		ListCell   *lc;
  
  		/*
  		 * Is there a Var for it in rel's targetlist?  If not, the query did
  		 * not reference the ordinality column, or at least not in any way
  		 * that would be interesting for sorting.
  		 */
  		foreach(lc, rel->reltarget->exprs)
  		{
  			Var		   *node = (Var *) lfirst(lc);
  
  			/* checking varno/varlevelsup is just paranoia */
  			if (IsA(node, Var) &&
  				node->varattno == ordattno &&
  				node->varno == rel->relid &&
  				node->varlevelsup == 0)
  			{
  				var = node;
  				break;
  			}
  		}
  
  		/*
  		 * Try to build pathkeys for this Var with int8 sorting.  We tell
  		 * build_expression_pathkey not to build any new equivalence class; if
  		 * the Var isn't already mentioned in some EC, it means that nothing
  		 * cares about the ordering.
  		 */
  		if (var)
  			pathkeys = build_expression_pathkey(root,
  												(Expr *) var,
  												NULL,	/* below outer joins */
  												Int8LessOperator,
  												rel->relids,
  												false);
  	}
  
  	/* Generate appropriate path */
  	add_path(rel, create_functionscan_path(root, rel,
  										   pathkeys, required_outer));
  }
  
  /*
   * set_values_pathlist
   *		Build the (single) access path for a VALUES RTE
   */
  static void
  set_values_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
  	Relids		required_outer;
  
  	/*
  	 * We don't support pushing join clauses into the quals of a values scan,
  	 * but it could still have required parameterization due to LATERAL refs
  	 * in the values expressions.
  	 */
  	required_outer = rel->lateral_relids;
  
  	/* Generate appropriate path */
  	add_path(rel, create_valuesscan_path(root, rel, required_outer));
  }
  
  /*
   * set_tablefunc_pathlist
   *		Build the (single) access path for a table func RTE
   */
  static void
  set_tablefunc_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
  	Relids		required_outer;
  
  	/*
  	 * We don't support pushing join clauses into the quals of a tablefunc
  	 * scan, but it could still have required parameterization due to LATERAL
  	 * refs in the function expression.
  	 */
  	required_outer = rel->lateral_relids;
  
  	/* Generate appropriate path */
  	add_path(rel, create_tablefuncscan_path(root, rel,
  											required_outer));
  }
  
  /*
   * set_cte_pathlist
   *		Build the (single) access path for a non-self-reference CTE RTE
   *
   * There's no need for a separate set_cte_size phase, since we don't
   * support join-qual-parameterized paths for CTEs.
   */
  static void
  set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
  	Plan	   *cteplan;
  	PlannerInfo *cteroot;
  	Index		levelsup;
  	int			ndx;
  	ListCell   *lc;
  	int			plan_id;
  	Relids		required_outer;
  
  	/*
  	 * Find the referenced CTE, and locate the plan previously made for it.
  	 */
  	levelsup = rte->ctelevelsup;
  	cteroot = root;
  	while (levelsup-- > 0)
  	{
  		cteroot = cteroot->parent_root;
  		if (!cteroot)			/* shouldn't happen */
  			elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
  	}
  
  	/*
  	 * Note: cte_plan_ids can be shorter than cteList, if we are still working
  	 * on planning the CTEs (ie, this is a side-reference from another CTE).
  	 * So we mustn't use forboth here.
  	 */
  	ndx = 0;
  	foreach(lc, cteroot->parse->cteList)
  	{
  		CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);
  
  		if (strcmp(cte->ctename, rte->ctename) == 0)
  			break;
  		ndx++;
  	}
  	if (lc == NULL)				/* shouldn't happen */
  		elog(ERROR, "could not find CTE \"%s\"", rte->ctename);
  	if (ndx >= list_length(cteroot->cte_plan_ids))
  		elog(ERROR, "could not find plan for CTE \"%s\"", rte->ctename);
  	plan_id = list_nth_int(cteroot->cte_plan_ids, ndx);
  	Assert(plan_id > 0);
  	cteplan = (Plan *) list_nth(root->glob->subplans, plan_id - 1);
  
  	/* Mark rel with estimated output rows, width, etc */
  	set_cte_size_estimates(root, rel, cteplan->plan_rows);
  
  	/*
  	 * We don't support pushing join clauses into the quals of a CTE scan, but
  	 * it could still have required parameterization due to LATERAL refs in
  	 * its tlist.
  	 */
  	required_outer = rel->lateral_relids;
  
  	/* Generate appropriate path */
  	add_path(rel, create_ctescan_path(root, rel, required_outer));
  }
  
  /*
   * set_namedtuplestore_pathlist
   *		Build the (single) access path for a named tuplestore RTE
   *
   * There's no need for a separate set_namedtuplestore_size phase, since we
   * don't support join-qual-parameterized paths for tuplestores.
   */
  static void
  set_namedtuplestore_pathlist(PlannerInfo *root, RelOptInfo *rel,
  							 RangeTblEntry *rte)
  {
  	Relids		required_outer;
  
  	/* Mark rel with estimated output rows, width, etc */
  	set_namedtuplestore_size_estimates(root, rel);
  
  	/*
  	 * We don't support pushing join clauses into the quals of a tuplestore
  	 * scan, but it could still have required parameterization due to LATERAL
  	 * refs in its tlist.
  	 */
  	required_outer = rel->lateral_relids;
  
  	/* Generate appropriate path */
  	add_path(rel, create_namedtuplestorescan_path(root, rel, required_outer));
  
  	/* Select cheapest path (pretty easy in this case...) */
  	set_cheapest(rel);
  }
  
  /*
   * set_worktable_pathlist
   *		Build the (single) access path for a self-reference CTE RTE
   *
   * There's no need for a separate set_worktable_size phase, since we don't
   * support join-qual-parameterized paths for CTEs.
   */
  static void
  set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
  {
  	Path	   *ctepath;
  	PlannerInfo *cteroot;
  	Index		levelsup;
  	Relids		required_outer;
  
  	/*
  	 * We need to find the non-recursive term's path, which is in the plan
  	 * level that's processing the recursive UNION, which is one level *below*
  	 * where the CTE comes from.
  	 */
  	levelsup = rte->ctelevelsup;
  	if (levelsup == 0)			/* shouldn't happen */
  		elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
  	levelsup--;
  	cteroot = root;
  	while (levelsup-- > 0)
  	{
  		cteroot = cteroot->parent_root;
  		if (!cteroot)			/* shouldn't happen */
  			elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
  	}
  	ctepath = cteroot->non_recursive_path;
  	if (!ctepath)				/* shouldn't happen */
  		elog(ERROR, "could not find path for CTE \"%s\"", rte->ctename);
  
  	/* Mark rel with estimated output rows, width, etc */
  	set_cte_size_estimates(root, rel, ctepath->rows);
  
  	/*
  	 * We don't support pushing join clauses into the quals of a worktable
  	 * scan, but it could still have required parameterization due to LATERAL
  	 * refs in its tlist.  (I'm not sure this is actually possible given the
  	 * restrictions on recursive references, but it's easy enough to support.)
  	 */
  	required_outer = rel->lateral_relids;
  
  	/* Generate appropriate path */
  	add_path(rel, create_worktablescan_path(root, rel, required_outer));
  }
  
  /*
   * generate_gather_paths
   *		Generate parallel access paths for a relation by pushing a Gather or
   *		Gather Merge on top of a partial path.
   *
   * This must not be called until after we're done creating all partial paths
   * for the specified relation.  (Otherwise, add_partial_path might delete a
   * path that some GatherPath or GatherMergePath has a reference to.)
   */
  void
  generate_gather_paths(PlannerInfo *root, RelOptInfo *rel)
  {
  	Path	   *cheapest_partial_path;
  	Path	   *simple_gather_path;
  	ListCell   *lc;
  
  	/* If there are no partial paths, there's nothing to do here. */
  	if (rel->partial_pathlist == NIL)
  		return;
  
  	/*
  	 * The output of Gather is always unsorted, so there's only one partial
  	 * path of interest: the cheapest one.  That will be the one at the front
  	 * of partial_pathlist because of the way add_partial_path works.
  	 */
  	cheapest_partial_path = linitial(rel->partial_pathlist);
  	simple_gather_path = (Path *)
  		create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
  						   NULL, NULL);
  	add_path(rel, simple_gather_path);
  
  	/*
  	 * For each useful ordering, we can consider an order-preserving Gather
  	 * Merge.
  	 */
  	foreach(lc, rel->partial_pathlist)
  	{
  		Path	   *subpath = (Path *) lfirst(lc);
  		GatherMergePath *path;
  
  		if (subpath->pathkeys == NIL)
  			continue;
  
  		path = create_gather_merge_path(root, rel, subpath, rel->reltarget,
  										subpath->pathkeys, NULL, NULL);
  		add_path(rel, &path->path);
  	}
  }
  
  /*
   * make_rel_from_joinlist
   *	  Build access paths using a "joinlist" to guide the join path search.
   *
   * See comments for deconstruct_jointree() for definition of the joinlist
   * data structure.
   */
  static RelOptInfo *
  make_rel_from_joinlist(PlannerInfo *root, List *joinlist)
  {
  	int			levels_needed;
  	List	   *initial_rels;
  	ListCell   *jl;
  
  	/*
  	 * Count the number of child joinlist nodes.  This is the depth of the
  	 * dynamic-programming algorithm we must employ to consider all ways of
  	 * joining the child nodes.
  	 */
  	levels_needed = list_length(joinlist);
  
  	if (levels_needed <= 0)
  		return NULL;			/* nothing to do? */
  
  	/*
  	 * Construct a list of rels corresponding to the child joinlist nodes.
  	 * This may contain both base rels and rels constructed according to
  	 * sub-joinlists.
  	 */
  	initial_rels = NIL;
  	foreach(jl, joinlist)
  	{
  		Node	   *jlnode = (Node *) lfirst(jl);
  		RelOptInfo *thisrel;
  
  		if (IsA(jlnode, RangeTblRef))
  		{
  			int			varno = ((RangeTblRef *) jlnode)->rtindex;
  
  			thisrel = find_base_rel(root, varno);
  		}
  		else if (IsA(jlnode, List))
  		{
  			/* Recurse to handle subproblem */
  			thisrel = make_rel_from_joinlist(root, (List *) jlnode);
  		}
  		else
  		{
  			elog(ERROR, "unrecognized joinlist node type: %d",
  				 (int) nodeTag(jlnode));
  			thisrel = NULL;		/* keep compiler quiet */
  		}
  
  		initial_rels = lappend(initial_rels, thisrel);
  	}
  
  	if (levels_needed == 1)
  	{
  		/*
  		 * Single joinlist node, so we're done.
  		 */
  		return (RelOptInfo *) linitial(initial_rels);
  	}
  	else
  	{
  		/*
  		 * Consider the different orders in which we could join the rels,
  		 * using a plugin, GEQO, or the regular join search code.
  		 *
  		 * We put the initial_rels list into a PlannerInfo field because
  		 * has_legal_joinclause() needs to look at it (ugly :-().
  		 */
  		root->initial_rels = initial_rels;
  
  		if (join_search_hook)
  			return (*join_search_hook) (root, levels_needed, initial_rels);
  		else if (enable_geqo && levels_needed >= geqo_threshold)
  			return geqo(root, levels_needed, initial_rels);
  		else
  			return standard_join_search(root, levels_needed, initial_rels);
  	}
  }
  
  /*
   * standard_join_search
   *	  Find possible joinpaths for a query by successively finding ways
   *	  to join component relations into join relations.
   *
   * 'levels_needed' is the number of iterations needed, ie, the number of
   *		independent jointree items in the query.  This is > 1.
   *
   * 'initial_rels' is a list of RelOptInfo nodes for each independent
   *		jointree item.  These are the components to be joined together.
   *		Note that levels_needed == list_length(initial_rels).
   *
   * Returns the final level of join relations, i.e., the relation that is
   * the result of joining all the original relations together.
   * At least one implementation path must be provided for this relation and
   * all required sub-relations.
   *
   * To support loadable plugins that modify planner behavior by changing the
   * join searching algorithm, we provide a hook variable that lets a plugin
   * replace or supplement this function.  Any such hook must return the same
   * final join relation as the standard code would, but it might have a
   * different set of implementation paths attached, and only the sub-joinrels
   * needed for these paths need have been instantiated.
   *
   * Note to plugin authors: the functions invoked during standard_join_search()
   * modify root->join_rel_list and root->join_rel_hash.  If you want to do more
   * than one join-order search, you'll probably need to save and restore the
   * original states of those data structures.  See geqo_eval() for an example.
   */
  RelOptInfo *
  standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
  {
  	int			lev;
  	RelOptInfo *rel;
  
  	/*
  	 * This function cannot be invoked recursively within any one planning
  	 * problem, so join_rel_level[] can't be in use already.
  	 */
  	Assert(root->join_rel_level == NULL);
  
  	/*
  	 * We employ a simple "dynamic programming" algorithm: we first find all
  	 * ways to build joins of two jointree items, then all ways to build joins
  	 * of three items (from two-item joins and single items), then four-item
  	 * joins, and so on until we have considered all ways to join all the
  	 * items into one rel.
  	 *
  	 * root->join_rel_level[j] is a list of all the j-item rels.  Initially we
  	 * set root->join_rel_level[1] to represent all the single-jointree-item
  	 * relations.
  	 */
  	root->join_rel_level = (List **) palloc0((levels_needed + 1) * sizeof(List *));
  
  	root->join_rel_level[1] = initial_rels;
  
  	for (lev = 2; lev <= levels_needed; lev++)
  	{
  		ListCell   *lc;
  
  		/*
  		 * Determine all possible pairs of relations to be joined at this
  		 * level, and build paths for making each one from every available
  		 * pair of lower-level relations.
  		 */
  		join_search_one_level(root, lev);
  
  		/*
  		 * Run generate_partition_wise_join_paths() and
  		 * generate_gather_paths() for each just-processed joinrel.  We could
  		 * not do this earlier because both regular and partial paths can get
  		 * added to a particular joinrel at multiple times within
  		 * join_search_one_level.
  		 *
  		 * After that, we're done creating paths for the joinrel, so run
  		 * set_cheapest().
  		 */
  		foreach(lc, root->join_rel_level[lev])
  		{
  			rel = (RelOptInfo *) lfirst(lc);
  
  			/* Create paths for partition-wise joins. */
  			generate_partition_wise_join_paths(root, rel);
  
  			/* Create GatherPaths for any useful partial paths for rel */
  			generate_gather_paths(root, rel);
  
  			/* Find and save the cheapest paths for this rel */
  			set_cheapest(rel);
  
  #ifdef OPTIMIZER_DEBUG
  			debug_print_rel(root, rel);
  #endif
  		}
  	}
  
  	/*
  	 * We should have a single rel at the final level.
  	 */
  	if (root->join_rel_level[levels_needed] == NIL)
  		elog(ERROR, "failed to build any %d-way joins", levels_needed);
  	Assert(list_length(root->join_rel_level[levels_needed]) == 1);
  
  	rel = (RelOptInfo *) linitial(root->join_rel_level[levels_needed]);
  
  	root->join_rel_level = NULL;
  
  	return rel;
  }
  
  /*****************************************************************************
   *			PUSHING QUALS DOWN INTO SUBQUERIES
   *****************************************************************************/
  
  /*
   * subquery_is_pushdown_safe - is a subquery safe for pushing down quals?
   *
   * subquery is the particular component query being checked.  topquery
   * is the top component of a set-operations tree (the same Query if no
   * set-op is involved).
   *
   * Conditions checked here:
   *
   * 1. If the subquery has a LIMIT clause, we must not push down any quals,
   * since that could change the set of rows returned.
   *
   * 2. If the subquery contains EXCEPT or EXCEPT ALL set ops we cannot push
   * quals into it, because that could change the results.
   *
   * 3. If the subquery uses DISTINCT, we cannot push volatile quals into it.
   * This is because upper-level quals should semantically be evaluated only
   * once per distinct row, not once per original row, and if the qual is
   * volatile then extra evaluations could change the results.  (This issue
   * does not apply to other forms of aggregation such as GROUP BY, because
   * when those are present we push into HAVING not WHERE, so that the quals
   * are still applied after aggregation.)
   *
   * 4. If the subquery contains window functions, we cannot push volatile quals
   * into it.  The issue here is a bit different from DISTINCT: a volatile qual
   * might succeed for some rows of a window partition and fail for others,
   * thereby changing the partition contents and thus the window functions'
   * results for rows that remain.
   *
   * 5. If the subquery contains any set-returning functions in its targetlist,
   * we cannot push volatile quals into it.  That would push them below the SRFs
   * and thereby change the number of times they are evaluated.  Also, a
   * volatile qual could succeed for some SRF output rows and fail for others,
   * a behavior that cannot occur if it's evaluated before SRF expansion.
   *
   * In addition, we make several checks on the subquery's output columns to see
   * if it is safe to reference them in pushed-down quals.  If output column k
   * is found to be unsafe to reference, we set safetyInfo->unsafeColumns[k]
   * to true, but we don't reject the subquery overall since column k might not
   * be referenced by some/all quals.  The unsafeColumns[] array will be
   * consulted later by qual_is_pushdown_safe().  It's better to do it this way
   * than to make the checks directly in qual_is_pushdown_safe(), because when
   * the subquery involves set operations we have to check the output
   * expressions in each arm of the set op.
   *
   * Note: pushing quals into a DISTINCT subquery is theoretically dubious:
   * we're effectively assuming that the quals cannot distinguish values that
   * the DISTINCT's equality operator sees as equal, yet there are many
   * counterexamples to that assumption.  However use of such a qual with a
   * DISTINCT subquery would be unsafe anyway, since there's no guarantee which
   * "equal" value will be chosen as the output value by the DISTINCT operation.
   * So we don't worry too much about that.  Another objection is that if the
   * qual is expensive to evaluate, running it for each original row might cost
   * more than we save by eliminating rows before the DISTINCT step.  But it
   * would be very hard to estimate that at this stage, and in practice pushdown
   * seldom seems to make things worse, so we ignore that problem too.
   *
   * Note: likewise, pushing quals into a subquery with window functions is a
   * bit dubious: the quals might remove some rows of a window partition while
   * leaving others, causing changes in the window functions' results for the
   * surviving rows.  We insist that such a qual reference only partitioning
   * columns, but again that only protects us if the qual does not distinguish
   * values that the partitioning equality operator sees as equal.  The risks
   * here are perhaps larger than for DISTINCT, since no de-duplication of rows
   * occurs and thus there is no theoretical problem with such a qual.  But
   * we'll do this anyway because the potential performance benefits are very
   * large, and we've seen no field complaints about the longstanding comparable
   * behavior with DISTINCT.
   */
  static bool
  subquery_is_pushdown_safe(Query *subquery, Query *topquery,
  						  pushdown_safety_info *safetyInfo)
  {
  	SetOperationStmt *topop;
  
  	/* Check point 1 */
  	if (subquery->limitOffset != NULL || subquery->limitCount != NULL)
  		return false;
  
  	/* Check points 3, 4, and 5 */
  	if (subquery->distinctClause ||
  		subquery->hasWindowFuncs ||
  		subquery->hasTargetSRFs)
  		safetyInfo->unsafeVolatile = true;
  
  	/*
  	 * If we're at a leaf query, check for unsafe expressions in its target
  	 * list, and mark any unsafe ones in unsafeColumns[].  (Non-leaf nodes in
  	 * setop trees have only simple Vars in their tlists, so no need to check
  	 * them.)
  	 */
  	if (subquery->setOperations == NULL)
  		check_output_expressions(subquery, safetyInfo);
  
  	/* Are we at top level, or looking at a setop component? */
  	if (subquery == topquery)
  	{
  		/* Top level, so check any component queries */
  		if (subquery->setOperations != NULL)
  			if (!recurse_pushdown_safe(subquery->setOperations, topquery,
  									   safetyInfo))
  				return false;
  	}
  	else
  	{
  		/* Setop component must not have more components (too weird) */
  		if (subquery->setOperations != NULL)
  			return false;
  		/* Check whether setop component output types match top level */
  		topop = castNode(SetOperationStmt, topquery->setOperations);
  		Assert(topop);
  		compare_tlist_datatypes(subquery->targetList,
  								topop->colTypes,
  								safetyInfo);
  	}
  	return true;
  }
  
  /*
   * Helper routine to recurse through setOperations tree
   */
  static bool
  recurse_pushdown_safe(Node *setOp, Query *topquery,
  					  pushdown_safety_info *safetyInfo)
  {
  	if (IsA(setOp, RangeTblRef))
  	{
  		RangeTblRef *rtr = (RangeTblRef *) setOp;
  		RangeTblEntry *rte = rt_fetch(rtr->rtindex, topquery->rtable);
  		Query	   *subquery = rte->subquery;
  
  		Assert(subquery != NULL);
  		return subquery_is_pushdown_safe(subquery, topquery, safetyInfo);
  	}
  	else if (IsA(setOp, SetOperationStmt))
  	{
  		SetOperationStmt *op = (SetOperationStmt *) setOp;
  
  		/* EXCEPT is no good (point 2 for subquery_is_pushdown_safe) */
  		if (op->op == SETOP_EXCEPT)
  			return false;
  		/* Else recurse */
  		if (!recurse_pushdown_safe(op->larg, topquery, safetyInfo))
  			return false;
  		if (!recurse_pushdown_safe(op->rarg, topquery, safetyInfo))
  			return false;
  	}
  	else
  	{
  		elog(ERROR, "unrecognized node type: %d",
  			 (int) nodeTag(setOp));
  	}
  	return true;
  }
  
  /*
   * check_output_expressions - check subquery's output expressions for safety
   *
   * There are several cases in which it's unsafe to push down an upper-level
   * qual if it references a particular output column of a subquery.  We check
   * each output column of the subquery and set unsafeColumns[k] to true if
   * that column is unsafe for a pushed-down qual to reference.  The conditions
   * checked here are:
   *
   * 1. We must not push down any quals that refer to subselect outputs that
   * return sets, else we'd introduce functions-returning-sets into the
   * subquery's WHERE/HAVING quals.
   *
   * 2. We must not push down any quals that refer to subselect outputs that
   * contain volatile functions, for fear of introducing strange results due
   * to multiple evaluation of a volatile function.
   *
   * 3. If the subquery uses DISTINCT ON, we must not push down any quals that
   * refer to non-DISTINCT output columns, because that could change the set
   * of rows returned.  (This condition is vacuous for DISTINCT, because then
   * there are no non-DISTINCT output columns, so we needn't check.  Note that
   * subquery_is_pushdown_safe already reported that we can't use volatile
   * quals if there's DISTINCT or DISTINCT ON.)
   *
   * 4. If the subquery has any window functions, we must not push down quals
   * that reference any output columns that are not listed in all the subquery's
   * window PARTITION BY clauses.  We can push down quals that use only
   * partitioning columns because they should succeed or fail identically for
   * every row of any one window partition, and totally excluding some
   * partitions will not change a window function's results for remaining
   * partitions.  (Again, this also requires nonvolatile quals, but
   * subquery_is_pushdown_safe handles that.)
   */
  static void
  check_output_expressions(Query *subquery, pushdown_safety_info *safetyInfo)
  {
  	ListCell   *lc;
  
  	foreach(lc, subquery->targetList)
  	{
  		TargetEntry *tle = (TargetEntry *) lfirst(lc);
  
  		if (tle->resjunk)
  			continue;			/* ignore resjunk columns */
  
  		/* We need not check further if output col is already known unsafe */
  		if (safetyInfo->unsafeColumns[tle->resno])
  			continue;
  
  		/* Functions returning sets are unsafe (point 1) */
  		if (subquery->hasTargetSRFs &&
  			expression_returns_set((Node *) tle->expr))
  		{
  			safetyInfo->unsafeColumns[tle->resno] = true;
  			continue;
  		}
  
  		/* Volatile functions are unsafe (point 2) */
  		if (contain_volatile_functions((Node *) tle->expr))
  		{
  			safetyInfo->unsafeColumns[tle->resno] = true;
  			continue;
  		}
  
  		/* If subquery uses DISTINCT ON, check point 3 */
  		if (subquery->hasDistinctOn &&
  			!targetIsInSortList(tle, InvalidOid, subquery->distinctClause))
  		{
  			/* non-DISTINCT column, so mark it unsafe */
  			safetyInfo->unsafeColumns[tle->resno] = true;
  			continue;
  		}
  
  		/* If subquery uses window functions, check point 4 */
  		if (subquery->hasWindowFuncs &&
  			!targetIsInAllPartitionLists(tle, subquery))
  		{
  			/* not present in all PARTITION BY clauses, so mark it unsafe */
  			safetyInfo->unsafeColumns[tle->resno] = true;
  			continue;
  		}
  	}
  }
  
  /*
   * For subqueries using UNION/UNION ALL/INTERSECT/INTERSECT ALL, we can
   * push quals into each component query, but the quals can only reference
   * subquery columns that suffer no type coercions in the set operation.
   * Otherwise there are possible semantic gotchas.  So, we check the
   * component queries to see if any of them have output types different from
   * the top-level setop outputs.  unsafeColumns[k] is set true if column k
   * has different type in any component.
   *
   * We don't have to care about typmods here: the only allowed difference
   * between set-op input and output typmods is input is a specific typmod
   * and output is -1, and that does not require a coercion.
   *
   * tlist is a subquery tlist.
   * colTypes is an OID list of the top-level setop's output column types.
   * safetyInfo->unsafeColumns[] is the result array.
   */
  static void
  compare_tlist_datatypes(List *tlist, List *colTypes,
  						pushdown_safety_info *safetyInfo)
  {
  	ListCell   *l;
  	ListCell   *colType = list_head(colTypes);
  
  	foreach(l, tlist)
  	{
  		TargetEntry *tle = (TargetEntry *) lfirst(l);
  
  		if (tle->resjunk)
  			continue;			/* ignore resjunk columns */
  		if (colType == NULL)
  			elog(ERROR, "wrong number of tlist entries");
  		if (exprType((Node *) tle->expr) != lfirst_oid(colType))
  			safetyInfo->unsafeColumns[tle->resno] = true;
  		colType = lnext(colType);
  	}
  	if (colType != NULL)
  		elog(ERROR, "wrong number of tlist entries");
  }
  
  /*
   * targetIsInAllPartitionLists
   *		True if the TargetEntry is listed in the PARTITION BY clause
   *		of every window defined in the query.
   *
   * It would be safe to ignore windows not actually used by any window
   * function, but it's not easy to get that info at this stage; and it's
   * unlikely to be useful to spend any extra cycles getting it, since
   * unreferenced window definitions are probably infrequent in practice.
   */
  static bool
  targetIsInAllPartitionLists(TargetEntry *tle, Query *query)
  {
  	ListCell   *lc;
  
  	foreach(lc, query->windowClause)
  	{
  		WindowClause *wc = (WindowClause *) lfirst(lc);
  
  		if (!targetIsInSortList(tle, InvalidOid, wc->partitionClause))
  			return false;
  	}
  	return true;
  }
  
  /*
   * qual_is_pushdown_safe - is a particular qual safe to push down?
   *
   * qual is a restriction clause applying to the given subquery (whose RTE
   * has index rti in the parent query).
   *
   * Conditions checked here:
   *
   * 1. The qual must not contain any SubPlans (mainly because I'm not sure
   * it will work correctly: SubLinks will already have been transformed into
   * SubPlans in the qual, but not in the subquery).  Note that SubLinks that
   * transform to initplans are safe, and will be accepted here because what
   * we'll see in the qual is just a Param referencing the initplan output.
   *
   * 2. If unsafeVolatile is set, the qual must not contain any volatile
   * functions.
   *
   * 3. If unsafeLeaky is set, the qual must not contain any leaky functions
   * that are passed Var nodes, and therefore might reveal values from the
   * subquery as side effects.
   *
   * 4. The qual must not refer to the whole-row output of the subquery
   * (since there is no easy way to name that within the subquery itself).
   *
   * 5. The qual must not refer to any subquery output columns that were
   * found to be unsafe to reference by subquery_is_pushdown_safe().
   */
  static bool
  qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
  					  pushdown_safety_info *safetyInfo)
  {
  	bool		safe = true;
  	List	   *vars;
  	ListCell   *vl;
  
  	/* Refuse subselects (point 1) */
  	if (contain_subplans(qual))
  		return false;
  
  	/* Refuse volatile quals if we found they'd be unsafe (point 2) */
  	if (safetyInfo->unsafeVolatile &&
  		contain_volatile_functions(qual))
  		return false;
  
  	/* Refuse leaky quals if told to (point 3) */
  	if (safetyInfo->unsafeLeaky &&
  		contain_leaked_vars(qual))
  		return false;
  
  	/*
  	 * It would be unsafe to push down window function calls, but at least for
  	 * the moment we could never see any in a qual anyhow.  (The same applies
  	 * to aggregates, which we check for in pull_var_clause below.)
  	 */
  	Assert(!contain_window_function(qual));
  
  	/*
  	 * Examine all Vars used in clause; since it's a restriction clause, all
  	 * such Vars must refer to subselect output columns.
  	 */
  	vars = pull_var_clause(qual, PVC_INCLUDE_PLACEHOLDERS);
  	foreach(vl, vars)
  	{
  		Var		   *var = (Var *) lfirst(vl);
  
  		/*
  		 * XXX Punt if we find any PlaceHolderVars in the restriction clause.
  		 * It's not clear whether a PHV could safely be pushed down, and even
  		 * less clear whether such a situation could arise in any cases of
  		 * practical interest anyway.  So for the moment, just refuse to push
  		 * down.
  		 */
  		if (!IsA(var, Var))
  		{
  			safe = false;
  			break;
  		}
  
  		Assert(var->varno == rti);
  		Assert(var->varattno >= 0);
  
  		/* Check point 4 */
  		if (var->varattno == 0)
  		{
  			safe = false;
  			break;
  		}
  
  		/* Check point 5 */
  		if (safetyInfo->unsafeColumns[var->varattno])
  		{
  			safe = false;
  			break;
  		}
  	}
  
  	list_free(vars);
  
  	return safe;
  }
  
  /*
   * subquery_push_qual - push down a qual that we have determined is safe
   */
  static void
  subquery_push_qual(Query *subquery, RangeTblEntry *rte, Index rti, Node *qual)
  {
  	if (subquery->setOperations != NULL)
  	{
  		/* Recurse to push it separately to each component query */
  		recurse_push_qual(subquery->setOperations, subquery,
  						  rte, rti, qual);
  	}
  	else
  	{
  		/*
  		 * We need to replace Vars in the qual (which must refer to outputs of
  		 * the subquery) with copies of the subquery's targetlist expressions.
  		 * Note that at this point, any uplevel Vars in the qual should have
  		 * been replaced with Params, so they need no work.
  		 *
  		 * This step also ensures that when we are pushing into a setop tree,
  		 * each component query gets its own copy of the qual.
  		 */
  		qual = ReplaceVarsFromTargetList(qual, rti, 0, rte,
  										 subquery->targetList,
  										 REPLACEVARS_REPORT_ERROR, 0,
  										 &subquery->hasSubLinks);
  
  		/*
  		 * Now attach the qual to the proper place: normally WHERE, but if the
  		 * subquery uses grouping or aggregation, put it in HAVING (since the
  		 * qual really refers to the group-result rows).
  		 */
  		if (subquery->hasAggs || subquery->groupClause || subquery->groupingSets || subquery->havingQual)
  			subquery->havingQual = make_and_qual(subquery->havingQual, qual);
  		else
  			subquery->jointree->quals =
  				make_and_qual(subquery->jointree->quals, qual);
  
  		/*
  		 * We need not change the subquery's hasAggs or hasSubLinks flags,
  		 * since we can't be pushing down any aggregates that weren't there
  		 * before, and we don't push down subselects at all.
  		 */
  	}
  }
  
  /*
   * Helper routine to recurse through setOperations tree
   */
  static void
  recurse_push_qual(Node *setOp, Query *topquery,
  				  RangeTblEntry *rte, Index rti, Node *qual)
  {
  	if (IsA(setOp, RangeTblRef))
  	{
  		RangeTblRef *rtr = (RangeTblRef *) setOp;
  		RangeTblEntry *subrte = rt_fetch(rtr->rtindex, topquery->rtable);
  		Query	   *subquery = subrte->subquery;
  
  		Assert(subquery != NULL);
  		subquery_push_qual(subquery, rte, rti, qual);
  	}
  	else if (IsA(setOp, SetOperationStmt))
  	{
  		SetOperationStmt *op = (SetOperationStmt *) setOp;
  
  		recurse_push_qual(op->larg, topquery, rte, rti, qual);
  		recurse_push_qual(op->rarg, topquery, rte, rti, qual);
  	}
  	else
  	{
  		elog(ERROR, "unrecognized node type: %d",
  			 (int) nodeTag(setOp));
  	}
  }
  
  /*****************************************************************************
   *			SIMPLIFYING SUBQUERY TARGETLISTS
   *****************************************************************************/
  
  /*
   * remove_unused_subquery_outputs
   *		Remove subquery targetlist items we don't need
   *
   * It's possible, even likely, that the upper query does not read all the
   * output columns of the subquery.  We can remove any such outputs that are
   * not needed by the subquery itself (e.g., as sort/group columns) and do not
   * affect semantics otherwise (e.g., volatile functions can't be removed).
   * This is useful not only because we might be able to remove expensive-to-
   * compute expressions, but because deletion of output columns might allow
   * optimizations such as join removal to occur within the subquery.
   *
   * To avoid affecting column numbering in the targetlist, we don't physically
   * remove unused tlist entries, but rather replace their expressions with NULL
   * constants.  This is implemented by modifying subquery->targetList.
   */
  static void
  remove_unused_subquery_outputs(Query *subquery, RelOptInfo *rel)
  {
  	Bitmapset  *attrs_used = NULL;
  	ListCell   *lc;
  
  	/*
  	 * Do nothing if subquery has UNION/INTERSECT/EXCEPT: in principle we
  	 * could update all the child SELECTs' tlists, but it seems not worth the
  	 * trouble presently.
  	 */
  	if (subquery->setOperations)
  		return;
  
  	/*
  	 * If subquery has regular DISTINCT (not DISTINCT ON), we're wasting our
  	 * time: all its output columns must be used in the distinctClause.
  	 */
  	if (subquery->distinctClause && !subquery->hasDistinctOn)
  		return;
  
  	/*
  	 * Collect a bitmap of all the output column numbers used by the upper
  	 * query.
  	 *
  	 * Add all the attributes needed for joins or final output.  Note: we must
  	 * look at rel's targetlist, not the attr_needed data, because attr_needed
  	 * isn't computed for inheritance child rels, cf set_append_rel_size().
  	 * (XXX might be worth changing that sometime.)
  	 */
  	pull_varattnos((Node *) rel->reltarget->exprs, rel->relid, &attrs_used);
  
  	/* Add all the attributes used by un-pushed-down restriction clauses. */
  	foreach(lc, rel->baserestrictinfo)
  	{
  		RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
  
  		pull_varattnos((Node *) rinfo->clause, rel->relid, &attrs_used);
  	}
  
  	/*
  	 * If there's a whole-row reference to the subquery, we can't remove
  	 * anything.
  	 */
  	if (bms_is_member(0 - FirstLowInvalidHeapAttributeNumber, attrs_used))
  		return;
  
  	/*
  	 * Run through the tlist and zap entries we don't need.  It's okay to
  	 * modify the tlist items in-place because set_subquery_pathlist made a
  	 * copy of the subquery.
  	 */
  	foreach(lc, subquery->targetList)
  	{
  		TargetEntry *tle = (TargetEntry *) lfirst(lc);
  		Node	   *texpr = (Node *) tle->expr;
  
  		/*
  		 * If it has a sortgroupref number, it's used in some sort/group
  		 * clause so we'd better not remove it.  Also, don't remove any
  		 * resjunk columns, since their reason for being has nothing to do
  		 * with anybody reading the subquery's output.  (It's likely that
  		 * resjunk columns in a sub-SELECT would always have ressortgroupref
  		 * set, but even if they don't, it seems imprudent to remove them.)
  		 */
  		if (tle->ressortgroupref || tle->resjunk)
  			continue;
  
  		/*
  		 * If it's used by the upper query, we can't remove it.
  		 */
  		if (bms_is_member(tle->resno - FirstLowInvalidHeapAttributeNumber,
  						  attrs_used))
  			continue;
  
  		/*
  		 * If it contains a set-returning function, we can't remove it since
  		 * that could change the number of rows returned by the subquery.
  		 */
  		if (subquery->hasTargetSRFs &&
  			expression_returns_set(texpr))
  			continue;
  
  		/*
  		 * If it contains volatile functions, we daren't remove it for fear
  		 * that the user is expecting their side-effects to happen.
  		 */
  		if (contain_volatile_functions(texpr))
  			continue;
  
  		/*
  		 * OK, we don't need it.  Replace the expression with a NULL constant.
  		 * Preserve the exposed type of the expression, in case something
  		 * looks at the rowtype of the subquery's result.
  		 */
  		tle->expr = (Expr *) makeNullConst(exprType(texpr),
  										   exprTypmod(texpr),
  										   exprCollation(texpr));
  	}
  }
  
  /*
   * create_partial_bitmap_paths
   *	  Build partial bitmap heap path for the relation
   */
  void
  create_partial_bitmap_paths(PlannerInfo *root, RelOptInfo *rel,
  							Path *bitmapqual)
  {
  	int			parallel_workers;
  	double		pages_fetched;
  
  	/* Compute heap pages for bitmap heap scan */
  	pages_fetched = compute_bitmap_pages(root, rel, bitmapqual, 1.0,
  										 NULL, NULL);
  
  	parallel_workers = compute_parallel_worker(rel, pages_fetched, -1);
  
  	if (parallel_workers <= 0)
  		return;
  
  	add_partial_path(rel, (Path *) create_bitmap_heap_path(root, rel,
  														   bitmapqual, rel->lateral_relids, 1.0, parallel_workers));
  }
  
  /*
   * Compute the number of parallel workers that should be used to scan a
   * relation.  We compute the parallel workers based on the size of the heap to
   * be scanned and the size of the index to be scanned, then choose a minimum
   * of those.
   *
   * "heap_pages" is the number of pages from the table that we expect to scan, or
   * -1 if we don't expect to scan any.
   *
   * "index_pages" is the number of pages from the index that we expect to scan, or
   * -1 if we don't expect to scan any.
   */
  int
  compute_parallel_worker(RelOptInfo *rel, double heap_pages, double index_pages)
  {
  	int			parallel_workers = 0;
  
  	/*
  	 * If the user has set the parallel_workers reloption, use that; otherwise
  	 * select a default number of workers.
  	 */
  	if (rel->rel_parallel_workers != -1)
  		parallel_workers = rel->rel_parallel_workers;
  	else
  	{
  		/*
  		 * If the number of pages being scanned is insufficient to justify a
  		 * parallel scan, just return zero ... unless it's an inheritance
  		 * child. In that case, we want to generate a parallel path here
  		 * anyway.  It might not be worthwhile just for this relation, but
  		 * when combined with all of its inheritance siblings it may well pay
  		 * off.
  		 */
  		if (rel->reloptkind == RELOPT_BASEREL &&
  			((heap_pages >= 0 && heap_pages < min_parallel_table_scan_size) ||
  			 (index_pages >= 0 && index_pages < min_parallel_index_scan_size)))
  			return 0;
  
  		if (heap_pages >= 0)
  		{
  			int			heap_parallel_threshold;
  			int			heap_parallel_workers = 1;
  
  			/*
  			 * Select the number of workers based on the log of the size of
  			 * the relation.  This probably needs to be a good deal more
  			 * sophisticated, but we need something here for now.  Note that
  			 * the upper limit of the min_parallel_table_scan_size GUC is
  			 * chosen to prevent overflow here.
  			 */
  			heap_parallel_threshold = Max(min_parallel_table_scan_size, 1);
  			while (heap_pages >= (BlockNumber) (heap_parallel_threshold * 3))
  			{
  				heap_parallel_workers++;
  				heap_parallel_threshold *= 3;
  				if (heap_parallel_threshold > INT_MAX / 3)
  					break;		/* avoid overflow */
  			}
  
  			parallel_workers = heap_parallel_workers;
  		}
  
  		if (index_pages >= 0)
  		{
  			int			index_parallel_workers = 1;
  			int			index_parallel_threshold;
  
  			/* same calculation as for heap_pages above */
  			index_parallel_threshold = Max(min_parallel_index_scan_size, 1);
  			while (index_pages >= (BlockNumber) (index_parallel_threshold * 3))
  			{
  				index_parallel_workers++;
  				index_parallel_threshold *= 3;
  				if (index_parallel_threshold > INT_MAX / 3)
  					break;		/* avoid overflow */
  			}
  
  			if (parallel_workers > 0)
  				parallel_workers = Min(parallel_workers, index_parallel_workers);
  			else
  				parallel_workers = index_parallel_workers;
  		}
  	}
  
  	/*
  	 * In no case use more than max_parallel_workers_per_gather workers.
  	 */
  	parallel_workers = Min(parallel_workers, max_parallel_workers_per_gather);
  
  	return parallel_workers;
  }
  
  /*
   * generate_partition_wise_join_paths
   * 		Create paths representing partition-wise join for given partitioned
   * 		join relation.
   *
   * This must not be called until after we are done adding paths for all
   * child-joins. Otherwise, add_path might delete a path to which some path
   * generated here has a reference.
   */
  void
  generate_partition_wise_join_paths(PlannerInfo *root, RelOptInfo *rel)
  {
  	List	   *live_children = NIL;
  	int			cnt_parts;
  	int			num_parts;
  	RelOptInfo **part_rels;
  
  	/* Handle only join relations here. */
  	if (!IS_JOIN_REL(rel))
  		return;
  
  	/*
  	 * If we've already proven this join is empty, we needn't consider any
  	 * more paths for it.
  	 */
  	if (IS_DUMMY_REL(rel))
  		return;
  
  	/*
  	 * We've nothing to do if the relation is not partitioned. An outer join
  	 * relation which had an empty inner relation in every pair will have the
  	 * rest of the partitioning properties set except the child-join
  	 * RelOptInfos. See try_partition_wise_join() for more details.
  	 */
  	if (rel->nparts <= 0 || rel->part_rels == NULL)
  		return;
  
  	/* Guard against stack overflow due to overly deep partition hierarchy. */
  	check_stack_depth();
  
  	num_parts = rel->nparts;
  	part_rels = rel->part_rels;
  
  	/* Collect non-dummy child-joins. */
  	for (cnt_parts = 0; cnt_parts < num_parts; cnt_parts++)
  	{
  		RelOptInfo *child_rel = part_rels[cnt_parts];
  
  		/* Add partition-wise join paths for partitioned child-joins. */
  		generate_partition_wise_join_paths(root, child_rel);
  
  		/* Dummy children will not be scanned, so ignore those. */
  		if (IS_DUMMY_REL(child_rel))
  			continue;
  
  		set_cheapest(child_rel);
  
  #ifdef OPTIMIZER_DEBUG
  		debug_print_rel(root, rel);
  #endif
  
  		live_children = lappend(live_children, child_rel);
  	}
  
  	/* If all child-joins are dummy, parent join is also dummy. */
  	if (!live_children)
  	{
  		mark_dummy_rel(rel);
  		return;
  	}
  
  	/* Build additional paths for this rel from child-join paths. */
  	add_paths_to_append_rel(root, rel, live_children);
  	list_free(live_children);
  }
  
  
  /*****************************************************************************
   *			DEBUG SUPPORT
   *****************************************************************************/
  
  #ifdef OPTIMIZER_DEBUG
  
  static void
  print_relids(PlannerInfo *root, Relids relids)
  {
  	int			x;
  	bool		first = true;
  
  	x = -1;
  	while ((x = bms_next_member(relids, x)) >= 0)
  	{
  		if (!first)
  			printf(" ");
  		if (x < root->simple_rel_array_size &&
  			root->simple_rte_array[x])
  			printf("%s", root->simple_rte_array[x]->eref->aliasname);
  		else
  			printf("%d", x);
  		first = false;
  	}
  }
  
  static void
  print_restrictclauses(PlannerInfo *root, List *clauses)
  {
  	ListCell   *l;
  
  	foreach(l, clauses)
  	{
  		RestrictInfo *c = lfirst(l);
  
  		print_expr((Node *) c->clause, root->parse->rtable);
  		if (lnext(l))
  			printf(", ");
  	}
  }
  
  static void
  print_path(PlannerInfo *root, Path *path, int indent)
  {
  	const char *ptype;
  	bool		join = false;
  	Path	   *subpath = NULL;
  	int			i;
  
  	switch (nodeTag(path))
  	{
  		case T_Path:
  			switch (path->pathtype)
  			{
  				case T_SeqScan:
  					ptype = "SeqScan";
  					break;
  				case T_SampleScan:
  					ptype = "SampleScan";
  					break;
  				case T_SubqueryScan:
  					ptype = "SubqueryScan";
  					break;
  				case T_FunctionScan:
  					ptype = "FunctionScan";
  					break;
  				case T_TableFuncScan:
  					ptype = "TableFuncScan";
  					break;
  				case T_ValuesScan:
  					ptype = "ValuesScan";
  					break;
  				case T_CteScan:
  					ptype = "CteScan";
  					break;
  				case T_WorkTableScan:
  					ptype = "WorkTableScan";
  					break;
  				default:
  					ptype = "???Path";
  					break;
  			}
  			break;
  		case T_IndexPath:
  			ptype = "IdxScan";
  			break;
  		case T_BitmapHeapPath:
  			ptype = "BitmapHeapScan";
  			break;
  		case T_BitmapAndPath:
  			ptype = "BitmapAndPath";
  			break;
  		case T_BitmapOrPath:
  			ptype = "BitmapOrPath";
  			break;
  		case T_TidPath:
  			ptype = "TidScan";
  			break;
  		case T_SubqueryScanPath:
  			ptype = "SubqueryScanScan";
  			break;
  		case T_ForeignPath:
  			ptype = "ForeignScan";
  			break;
  		case T_AppendPath:
  			ptype = "Append";
  			break;
  		case T_MergeAppendPath:
  			ptype = "MergeAppend";
  			break;
  		case T_ResultPath:
  			ptype = "Result";
  			break;
  		case T_MaterialPath:
  			ptype = "Material";
  			subpath = ((MaterialPath *) path)->subpath;
  			break;
  		case T_UniquePath:
  			ptype = "Unique";
  			subpath = ((UniquePath *) path)->subpath;
  			break;
  		case T_GatherPath:
  			ptype = "Gather";
  			subpath = ((GatherPath *) path)->subpath;
  			break;
  		case T_ProjectionPath:
  			ptype = "Projection";
  			subpath = ((ProjectionPath *) path)->subpath;
  			break;
  		case T_ProjectSetPath:
  			ptype = "ProjectSet";
  			subpath = ((ProjectSetPath *) path)->subpath;
  			break;
  		case T_SortPath:
  			ptype = "Sort";
  			subpath = ((SortPath *) path)->subpath;
  			break;
  		case T_GroupPath:
  			ptype = "Group";
  			subpath = ((GroupPath *) path)->subpath;
  			break;
  		case T_UpperUniquePath:
  			ptype = "UpperUnique";
  			subpath = ((UpperUniquePath *) path)->subpath;
  			break;
  		case T_AggPath:
  			ptype = "Agg";
  			subpath = ((AggPath *) path)->subpath;
  			break;
  		case T_GroupingSetsPath:
  			ptype = "GroupingSets";
  			subpath = ((GroupingSetsPath *) path)->subpath;
  			break;
  		case T_MinMaxAggPath:
  			ptype = "MinMaxAgg";
  			break;
  		case T_WindowAggPath:
  			ptype = "WindowAgg";
  			subpath = ((WindowAggPath *) path)->subpath;
  			break;
  		case T_SetOpPath:
  			ptype = "SetOp";
  			subpath = ((SetOpPath *) path)->subpath;
  			break;
  		case T_RecursiveUnionPath:
  			ptype = "RecursiveUnion";
  			break;
  		case T_LockRowsPath:
  			ptype = "LockRows";
  			subpath = ((LockRowsPath *) path)->subpath;
  			break;
  		case T_ModifyTablePath:
  			ptype = "ModifyTable";
  			break;
  		case T_LimitPath:
  			ptype = "Limit";
  			subpath = ((LimitPath *) path)->subpath;
  			break;
  		case T_NestPath:
  			ptype = "NestLoop";
  			join = true;
  			break;
  		case T_MergePath:
  			ptype = "MergeJoin";
  			join = true;
  			break;
  		case T_HashPath:
  			ptype = "HashJoin";
  			join = true;
  			break;
  		default:
  			ptype = "???Path";
  			break;
  	}
  
  	for (i = 0; i < indent; i++)
  		printf("\t");
  	printf("%s", ptype);
  
  	if (path->parent)
  	{
  		printf("(");
  		print_relids(root, path->parent->relids);
  		printf(")");
  	}
  	if (path->param_info)
  	{
  		printf(" required_outer (");
  		print_relids(root, path->param_info->ppi_req_outer);
  		printf(")");
  	}
  	printf(" rows=%.0f cost=%.2f..%.2f\n",
  		   path->rows, path->startup_cost, path->total_cost);
  
  	if (path->pathkeys)
  	{
  		for (i = 0; i < indent; i++)
  			printf("\t");
  		printf("  pathkeys: ");
  		print_pathkeys(path->pathkeys, root->parse->rtable);
  	}
  
  	if (join)
  	{
  		JoinPath   *jp = (JoinPath *) path;
  
  		for (i = 0; i < indent; i++)
  			printf("\t");
  		printf("  clauses: ");
  		print_restrictclauses(root, jp->joinrestrictinfo);
  		printf("\n");
  
  		if (IsA(path, MergePath))
  		{
  			MergePath  *mp = (MergePath *) path;
  
  			for (i = 0; i < indent; i++)
  				printf("\t");
  			printf("  sortouter=%d sortinner=%d materializeinner=%d\n",
  				   ((mp->outersortkeys) ? 1 : 0),
  				   ((mp->innersortkeys) ? 1 : 0),
  				   ((mp->materialize_inner) ? 1 : 0));
  		}
  
  		print_path(root, jp->outerjoinpath, indent + 1);
  		print_path(root, jp->innerjoinpath, indent + 1);
  	}
  
  	if (subpath)
  		print_path(root, subpath, indent + 1);
  }
  
  void
  debug_print_rel(PlannerInfo *root, RelOptInfo *rel)
  {
  	ListCell   *l;
  
  	printf("RELOPTINFO (");
  	print_relids(root, rel->relids);
  	printf("): rows=%.0f width=%d\n", rel->rows, rel->reltarget->width);
  
  	if (rel->baserestrictinfo)
  	{
  		printf("\tbaserestrictinfo: ");
  		print_restrictclauses(root, rel->baserestrictinfo);
  		printf("\n");
  	}
  
  	if (rel->joininfo)
  	{
  		printf("\tjoininfo: ");
  		print_restrictclauses(root, rel->joininfo);
  		printf("\n");
  	}
  
  	printf("\tpath list:\n");
  	foreach(l, rel->pathlist)
  		print_path(root, lfirst(l), 1);
  	if (rel->cheapest_parameterized_paths)
  	{
  		printf("\n\tcheapest parameterized paths:\n");
  		foreach(l, rel->cheapest_parameterized_paths)
  			print_path(root, lfirst(l), 1);
  	}
  	if (rel->cheapest_startup_path)
  	{
  		printf("\n\tcheapest startup path:\n");
  		print_path(root, rel->cheapest_startup_path, 1);
  	}
  	if (rel->cheapest_total_path)
  	{
  		printf("\n\tcheapest total path:\n");
  		print_path(root, rel->cheapest_total_path, 1);
  	}
  	printf("\n");
  	fflush(stdout);
  }
  
  #endif							/* OPTIMIZER_DEBUG */
  