text: /*-------------------------------------------------------------------------
   *
   * deparse.c
   *		  Query deparser for postgres_fdw
   *
   * This file includes functions that examine query WHERE clauses to see
   * whether they're safe to send to the remote server for execution, as
   * well as functions to construct the query text to be sent.  The latter
   * functionality is annoyingly duplicative of ruleutils.c, but there are
   * enough special considerations that it seems best to keep this separate.
   * One saving grace is that we only need deparse logic for node types that
   * we consider safe to send.
   *
   * We assume that the remote session's search_path is exactly "pg_catalog",
   * and thus we need schema-qualify all and only names outside pg_catalog.
   *
   * We do not consider that it is ever safe to send COLLATE expressions to
   * the remote server: it might not have the same collation names we do.
   * (Later we might consider it safe to send COLLATE "C", but even that would
   * fail on old remote servers.)  An expression is considered safe to send
   * only if all operator/function input collations used in it are traceable to
   * Var(s) of the foreign table.  That implies that if the remote server gets
   * a different answer than we do, the foreign table's columns are not marked
   * with collations that match the remote table's columns, which we can
   * consider to be user error.
   *
   * Portions Copyright (c) 2012-2016, PostgreSQL Global Development Group
   *
   * IDENTIFICATION
   *		  contrib/postgres_fdw/deparse.c
   *
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include "postgres_fdw.h"
  
  #include "access/heapam.h"
  #include "access/htup_details.h"
  #include "access/sysattr.h"
  #include "catalog/pg_aggregate.h"
  #include "catalog/pg_collation.h"
  #include "catalog/pg_namespace.h"
  #include "catalog/pg_operator.h"
  #include "catalog/pg_proc.h"
  #include "catalog/pg_type.h"
  #include "commands/defrem.h"
  #include "nodes/makefuncs.h"
  #include "nodes/nodeFuncs.h"
  #include "nodes/plannodes.h"
  #include "optimizer/clauses.h"
  #include "optimizer/prep.h"
  #include "optimizer/tlist.h"
  #include "optimizer/var.h"
  #include "parser/parsetree.h"
  #include "utils/builtins.h"
  #include "utils/lsyscache.h"
  #include "utils/rel.h"
  #include "utils/syscache.h"
  #include "utils/typcache.h"
  
  
  /*
   * Global context for foreign_expr_walker's search of an expression tree.
   */
  typedef struct foreign_glob_cxt
  {
  	PlannerInfo *root;			/* global planner state */
  	RelOptInfo *foreignrel;		/* the foreign relation we are planning for */
  	Relids		relids;			/* relids of base relations in the underlying
  								 * scan */
  } foreign_glob_cxt;
  
  /*
   * Local (per-tree-level) context for foreign_expr_walker's search.
   * This is concerned with identifying collations used in the expression.
   */
  typedef enum
  {
  	FDW_COLLATE_NONE,			/* expression is of a noncollatable type, or
  								 * it has default collation that is not
  								 * traceable to a foreign Var */
  	FDW_COLLATE_SAFE,			/* collation derives from a foreign Var */
  	FDW_COLLATE_UNSAFE			/* collation is non-default and derives from
  								 * something other than a foreign Var */
  } FDWCollateState;
  
  typedef struct foreign_loc_cxt
  {
  	Oid			collation;		/* OID of current collation, if any */
  	FDWCollateState state;		/* state of current collation choice */
  } foreign_loc_cxt;
  
  /*
   * Context for deparseExpr
   */
  typedef struct deparse_expr_cxt
  {
  	PlannerInfo *root;			/* global planner state */
  	RelOptInfo *foreignrel;		/* the foreign relation we are planning for */
  	RelOptInfo *scanrel;		/* the underlying scan relation. Same as
  								 * foreignrel, when that represents a join or
  								 * a base relation. */
  	StringInfo	buf;			/* output buffer to append to */
  	List	  **params_list;	/* exprs that will become remote Params */
  } deparse_expr_cxt;
  
  #define REL_ALIAS_PREFIX	"r"
  /* Handy macro to add relation name qualification */
  #define ADD_REL_QUALIFIER(buf, varno)	\
  		appendStringInfo((buf), "%s%d.", REL_ALIAS_PREFIX, (varno))
  
  /*
   * Functions to determine whether an expression can be evaluated safely on
   * remote server.
   */
  static bool foreign_expr_walker(Node *node,
  					foreign_glob_cxt *glob_cxt,
  					foreign_loc_cxt *outer_cxt);
  static char *deparse_type_name(Oid type_oid, int32 typemod);
  
  /*
   * Functions to construct string representation of a node tree.
   */
  static void deparseTargetList(StringInfo buf,
  				  PlannerInfo *root,
  				  Index rtindex,
  				  Relation rel,
  				  bool is_returning,
  				  Bitmapset *attrs_used,
  				  bool qualify_col,
  				  List **retrieved_attrs);
  static void deparseExplicitTargetList(List *tlist, List **retrieved_attrs,
  						  deparse_expr_cxt *context);
  static void deparseReturningList(StringInfo buf, PlannerInfo *root,
  					 Index rtindex, Relation rel,
  					 bool trig_after_row,
  					 List *returningList,
  					 List **retrieved_attrs);
  static void deparseColumnRef(StringInfo buf, int varno, int varattno,
  				 PlannerInfo *root, bool qualify_col);
  static void deparseRelation(StringInfo buf, Relation rel);
  static void deparseExpr(Expr *expr, deparse_expr_cxt *context);
  static void deparseVar(Var *node, deparse_expr_cxt *context);
  static void deparseConst(Const *node, deparse_expr_cxt *context, int showtype);
  static void deparseParam(Param *node, deparse_expr_cxt *context);
  static void deparseArrayRef(ArrayRef *node, deparse_expr_cxt *context);
  static void deparseFuncExpr(FuncExpr *node, deparse_expr_cxt *context);
  static void deparseOpExpr(OpExpr *node, deparse_expr_cxt *context);
  static void deparseOperatorName(StringInfo buf, Form_pg_operator opform);
  static void deparseDistinctExpr(DistinctExpr *node, deparse_expr_cxt *context);
  static void deparseScalarArrayOpExpr(ScalarArrayOpExpr *node,
  						 deparse_expr_cxt *context);
  static void deparseRelabelType(RelabelType *node, deparse_expr_cxt *context);
  static void deparseBoolExpr(BoolExpr *node, deparse_expr_cxt *context);
  static void deparseNullTest(NullTest *node, deparse_expr_cxt *context);
  static void deparseArrayExpr(ArrayExpr *node, deparse_expr_cxt *context);
  static void printRemoteParam(int paramindex, Oid paramtype, int32 paramtypmod,
  				 deparse_expr_cxt *context);
  static void printRemotePlaceholder(Oid paramtype, int32 paramtypmod,
  					   deparse_expr_cxt *context);
  static void deparseSelectSql(List *tlist, List **retrieved_attrs,
  				 deparse_expr_cxt *context);
  static void deparseLockingClause(deparse_expr_cxt *context);
  static void appendOrderByClause(List *pathkeys, deparse_expr_cxt *context);
  static void appendConditions(List *exprs, deparse_expr_cxt *context);
  static void deparseFromExprForRel(StringInfo buf, PlannerInfo *root,
  					RelOptInfo *joinrel, bool use_alias, List **params_list);
  static void deparseFromExpr(List *quals, deparse_expr_cxt *context);
  static void deparseAggref(Aggref *node, deparse_expr_cxt *context);
  static void appendGroupByClause(List *tlist, deparse_expr_cxt *context);
  static void appendAggOrderBy(List *orderList, List *targetList,
  				 deparse_expr_cxt *context);
  static void appendFunctionName(Oid funcid, deparse_expr_cxt *context);
  static Node *deparseSortGroupClause(Index ref, List *tlist,
  					   deparse_expr_cxt *context);
  
  
  /*
   * Examine each qual clause in input_conds, and classify them into two groups,
   * which are returned as two lists:
   *	- remote_conds contains expressions that can be evaluated remotely
   *	- local_conds contains expressions that can't be evaluated remotely
   */
  void
  classifyConditions(PlannerInfo *root,
  				   RelOptInfo *baserel,
  				   List *input_conds,
  				   List **remote_conds,
  				   List **local_conds)
  {
  	ListCell   *lc;
  
  	*remote_conds = NIL;
  	*local_conds = NIL;
  
  	foreach(lc, input_conds)
  	{
  		RestrictInfo *ri = (RestrictInfo *) lfirst(lc);
  
  		if (is_foreign_expr(root, baserel, ri->clause))
  			*remote_conds = lappend(*remote_conds, ri);
  		else
  			*local_conds = lappend(*local_conds, ri);
  	}
  }
  
  /*
   * Returns true if given expr is safe to evaluate on the foreign server.
   */
  bool
  is_foreign_expr(PlannerInfo *root,
  				RelOptInfo *baserel,
  				Expr *expr)
  {
  	foreign_glob_cxt glob_cxt;
  	foreign_loc_cxt loc_cxt;
  	PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) (baserel->fdw_private);
  
  	/*
  	 * Check that the expression consists of nodes that are safe to execute
  	 * remotely.
  	 */
  	glob_cxt.root = root;
  	glob_cxt.foreignrel = baserel;
  
  	/*
  	 * For an upper relation, use relids from its underneath scan relation,
  	 * because the upperrel's own relids currently aren't set to anything
  	 * meaningful by the core code.  For other relation, use their own relids.
  	 */
  	if (baserel->reloptkind == RELOPT_UPPER_REL)
  		glob_cxt.relids = fpinfo->outerrel->relids;
  	else
  		glob_cxt.relids = baserel->relids;
  	loc_cxt.collation = InvalidOid;
  	loc_cxt.state = FDW_COLLATE_NONE;
  	if (!foreign_expr_walker((Node *) expr, &glob_cxt, &loc_cxt))
  		return false;
  
  	/*
  	 * If the expression has a valid collation that does not arise from a
  	 * foreign var, the expression can not be sent over.
  	 */
  	if (loc_cxt.state == FDW_COLLATE_UNSAFE)
  		return false;
  
  	/*
  	 * An expression which includes any mutable functions can't be sent over
  	 * because its result is not stable.  For example, sending now() remote
  	 * side could cause confusion from clock offsets.  Future versions might
  	 * be able to make this choice with more granularity.  (We check this last
  	 * because it requires a lot of expensive catalog lookups.)
  	 */
  	if (contain_mutable_functions((Node *) expr))
  		return false;
  
  	/* OK to evaluate on the remote server */
  	return true;
  }
  
  /*
   * Check if expression is safe to execute remotely, and return true if so.
   *
   * In addition, *outer_cxt is updated with collation information.
   *
   * We must check that the expression contains only node types we can deparse,
   * that all types/functions/operators are safe to send (they are "shippable"),
   * and that all collations used in the expression derive from Vars of the
   * foreign table.  Because of the latter, the logic is pretty close to
   * assign_collations_walker() in parse_collate.c, though we can assume here
   * that the given expression is valid.  Note function mutability is not
   * currently considered here.
   */
  static bool
  foreign_expr_walker(Node *node,
  					foreign_glob_cxt *glob_cxt,
  					foreign_loc_cxt *outer_cxt)
  {
  	bool		check_type = true;
  	PgFdwRelationInfo *fpinfo;
  	foreign_loc_cxt inner_cxt;
  	Oid			collation;
  	FDWCollateState state;
  
  	/* Need do nothing for empty subexpressions */
  	if (node == NULL)
  		return true;
  
  	/* May need server info from baserel's fdw_private struct */
  	fpinfo = (PgFdwRelationInfo *) (glob_cxt->foreignrel->fdw_private);
  
  	/* Set up inner_cxt for possible recursion to child nodes */
  	inner_cxt.collation = InvalidOid;
  	inner_cxt.state = FDW_COLLATE_NONE;
  
  	switch (nodeTag(node))
  	{
  		case T_Var:
  			{
  				Var		   *var = (Var *) node;
  
  				/*
  				 * If the Var is from the foreign table, we consider its
  				 * collation (if any) safe to use.  If it is from another
  				 * table, we treat its collation the same way as we would a
  				 * Param's collation, ie it's not safe for it to have a
  				 * non-default collation.
  				 */
  				if (bms_is_member(var->varno, glob_cxt->relids) &&
  					var->varlevelsup == 0)
  				{
  					/* Var belongs to foreign table */
  
  					/*
  					 * System columns other than ctid and oid should not be
  					 * sent to the remote, since we don't make any effort to
  					 * ensure that local and remote values match (tableoid, in
  					 * particular, almost certainly doesn't match).
  					 */
  					if (var->varattno < 0 &&
  						var->varattno != SelfItemPointerAttributeNumber &&
  						var->varattno != ObjectIdAttributeNumber)
  						return false;
  
  					/* Else check the collation */
  					collation = var->varcollid;
  					state = OidIsValid(collation) ? FDW_COLLATE_SAFE : FDW_COLLATE_NONE;
  				}
  				else
  				{
  					/* Var belongs to some other table */
  					collation = var->varcollid;
  					if (collation == InvalidOid ||
  						collation == DEFAULT_COLLATION_OID)
  					{
  						/*
  						 * It's noncollatable, or it's safe to combine with a
  						 * collatable foreign Var, so set state to NONE.
  						 */
  						state = FDW_COLLATE_NONE;
  					}
  					else
  					{
  						/*
  						 * Do not fail right away, since the Var might appear
  						 * in a collation-insensitive context.
  						 */
  						state = FDW_COLLATE_UNSAFE;
  					}
  				}
  			}
  			break;
  		case T_Const:
  			{
  				Const	   *c = (Const *) node;
  
  				/*
  				 * If the constant has nondefault collation, either it's of a
  				 * non-builtin type, or it reflects folding of a CollateExpr.
  				 * It's unsafe to send to the remote unless it's used in a
  				 * non-collation-sensitive context.
  				 */
  				collation = c->constcollid;
  				if (collation == InvalidOid ||
  					collation == DEFAULT_COLLATION_OID)
  					state = FDW_COLLATE_NONE;
  				else
  					state = FDW_COLLATE_UNSAFE;
  			}
  			break;
  		case T_Param:
  			{
  				Param	   *p = (Param *) node;
  
  				/*
  				 * Collation rule is same as for Consts and non-foreign Vars.
  				 */
  				collation = p->paramcollid;
  				if (collation == InvalidOid ||
  					collation == DEFAULT_COLLATION_OID)
  					state = FDW_COLLATE_NONE;
  				else
  					state = FDW_COLLATE_UNSAFE;
  			}
  			break;
  		case T_ArrayRef:
  			{
  				ArrayRef   *ar = (ArrayRef *) node;
  
  				/* Assignment should not be in restrictions. */
  				if (ar->refassgnexpr != NULL)
  					return false;
  
  				/*
  				 * Recurse to remaining subexpressions.  Since the array
  				 * subscripts must yield (noncollatable) integers, they won't
  				 * affect the inner_cxt state.
  				 */
  				if (!foreign_expr_walker((Node *) ar->refupperindexpr,
  										 glob_cxt, &inner_cxt))
  					return false;
  				if (!foreign_expr_walker((Node *) ar->reflowerindexpr,
  										 glob_cxt, &inner_cxt))
  					return false;
  				if (!foreign_expr_walker((Node *) ar->refexpr,
  										 glob_cxt, &inner_cxt))
  					return false;
  
  				/*
  				 * Array subscripting should yield same collation as input,
  				 * but for safety use same logic as for function nodes.
  				 */
  				collation = ar->refcollid;
  				if (collation == InvalidOid)
  					state = FDW_COLLATE_NONE;
  				else if (inner_cxt.state == FDW_COLLATE_SAFE &&
  						 collation == inner_cxt.collation)
  					state = FDW_COLLATE_SAFE;
  				else if (collation == DEFAULT_COLLATION_OID)
  					state = FDW_COLLATE_NONE;
  				else
  					state = FDW_COLLATE_UNSAFE;
  			}
  			break;
  		case T_FuncExpr:
  			{
  				FuncExpr   *fe = (FuncExpr *) node;
  
  				/*
  				 * If function used by the expression is not shippable, it
  				 * can't be sent to remote because it might have incompatible
  				 * semantics on remote side.
  				 */
  				if (!is_shippable(fe->funcid, ProcedureRelationId, fpinfo))
  					return false;
  
  				/*
  				 * Recurse to input subexpressions.
  				 */
  				if (!foreign_expr_walker((Node *) fe->args,
  										 glob_cxt, &inner_cxt))
  					return false;
  
  				/*
  				 * If function's input collation is not derived from a foreign
  				 * Var, it can't be sent to remote.
  				 */
  				if (fe->inputcollid == InvalidOid)
  					 /* OK, inputs are all noncollatable */ ;
  				else if (inner_cxt.state != FDW_COLLATE_SAFE ||
  						 fe->inputcollid != inner_cxt.collation)
  					return false;
  
  				/*
  				 * Detect whether node is introducing a collation not derived
  				 * from a foreign Var.  (If so, we just mark it unsafe for now
  				 * rather than immediately returning false, since the parent
  				 * node might not care.)
  				 */
  				collation = fe->funccollid;
  				if (collation == InvalidOid)
  					state = FDW_COLLATE_NONE;
  				else if (inner_cxt.state == FDW_COLLATE_SAFE &&
  						 collation == inner_cxt.collation)
  					state = FDW_COLLATE_SAFE;
  				else if (collation == DEFAULT_COLLATION_OID)
  					state = FDW_COLLATE_NONE;
  				else
  					state = FDW_COLLATE_UNSAFE;
  			}
  			break;
  		case T_OpExpr:
  		case T_DistinctExpr:	/* struct-equivalent to OpExpr */
  			{
  				OpExpr	   *oe = (OpExpr *) node;
  
  				/*
  				 * Similarly, only shippable operators can be sent to remote.
  				 * (If the operator is shippable, we assume its underlying
  				 * function is too.)
  				 */
  				if (!is_shippable(oe->opno, OperatorRelationId, fpinfo))
  					return false;
  
  				/*
  				 * Recurse to input subexpressions.
  				 */
  				if (!foreign_expr_walker((Node *) oe->args,
  										 glob_cxt, &inner_cxt))
  					return false;
  
  				/*
  				 * If operator's input collation is not derived from a foreign
  				 * Var, it can't be sent to remote.
  				 */
  				if (oe->inputcollid == InvalidOid)
  					 /* OK, inputs are all noncollatable */ ;
  				else if (inner_cxt.state != FDW_COLLATE_SAFE ||
  						 oe->inputcollid != inner_cxt.collation)
  					return false;
  
  				/* Result-collation handling is same as for functions */
  				collation = oe->opcollid;
  				if (collation == InvalidOid)
  					state = FDW_COLLATE_NONE;
  				else if (inner_cxt.state == FDW_COLLATE_SAFE &&
  						 collation == inner_cxt.collation)
  					state = FDW_COLLATE_SAFE;
  				else if (collation == DEFAULT_COLLATION_OID)
  					state = FDW_COLLATE_NONE;
  				else
  					state = FDW_COLLATE_UNSAFE;
  			}
  			break;
  		case T_ScalarArrayOpExpr:
  			{
  				ScalarArrayOpExpr *oe = (ScalarArrayOpExpr *) node;
  
  				/*
  				 * Again, only shippable operators can be sent to remote.
  				 */
  				if (!is_shippable(oe->opno, OperatorRelationId, fpinfo))
  					return false;
  
  				/*
  				 * Recurse to input subexpressions.
  				 */
  				if (!foreign_expr_walker((Node *) oe->args,
  										 glob_cxt, &inner_cxt))
  					return false;
  
  				/*
  				 * If operator's input collation is not derived from a foreign
  				 * Var, it can't be sent to remote.
  				 */
  				if (oe->inputcollid == InvalidOid)
  					 /* OK, inputs are all noncollatable */ ;
  				else if (inner_cxt.state != FDW_COLLATE_SAFE ||
  						 oe->inputcollid != inner_cxt.collation)
  					return false;
  
  				/* Output is always boolean and so noncollatable. */
  				collation = InvalidOid;
  				state = FDW_COLLATE_NONE;
  			}
  			break;
  		case T_RelabelType:
  			{
  				RelabelType *r = (RelabelType *) node;
  
  				/*
  				 * Recurse to input subexpression.
  				 */
  				if (!foreign_expr_walker((Node *) r->arg,
  										 glob_cxt, &inner_cxt))
  					return false;
  
  				/*
  				 * RelabelType must not introduce a collation not derived from
  				 * an input foreign Var (same logic as for a real function).
  				 */
  				collation = r->resultcollid;
  				if (collation == InvalidOid)
  					state = FDW_COLLATE_NONE;
  				else if (inner_cxt.state == FDW_COLLATE_SAFE &&
  						 collation == inner_cxt.collation)
  					state = FDW_COLLATE_SAFE;
  				else if (collation == DEFAULT_COLLATION_OID)
  					state = FDW_COLLATE_NONE;
  				else
  					state = FDW_COLLATE_UNSAFE;
  			}
  			break;
  		case T_BoolExpr:
  			{
  				BoolExpr   *b = (BoolExpr *) node;
  
  				/*
  				 * Recurse to input subexpressions.
  				 */
  				if (!foreign_expr_walker((Node *) b->args,
  										 glob_cxt, &inner_cxt))
  					return false;
  
  				/* Output is always boolean and so noncollatable. */
  				collation = InvalidOid;
  				state = FDW_COLLATE_NONE;
  			}
  			break;
  		case T_NullTest:
  			{
  				NullTest   *nt = (NullTest *) node;
  
  				/*
  				 * Recurse to input subexpressions.
  				 */
  				if (!foreign_expr_walker((Node *) nt->arg,
  										 glob_cxt, &inner_cxt))
  					return false;
  
  				/* Output is always boolean and so noncollatable. */
  				collation = InvalidOid;
  				state = FDW_COLLATE_NONE;
  			}
  			break;
  		case T_ArrayExpr:
  			{
  				ArrayExpr  *a = (ArrayExpr *) node;
  
  				/*
  				 * Recurse to input subexpressions.
  				 */
  				if (!foreign_expr_walker((Node *) a->elements,
  										 glob_cxt, &inner_cxt))
  					return false;
  
  				/*
  				 * ArrayExpr must not introduce a collation not derived from
  				 * an input foreign Var (same logic as for a function).
  				 */
  				collation = a->array_collid;
  				if (collation == InvalidOid)
  					state = FDW_COLLATE_NONE;
  				else if (inner_cxt.state == FDW_COLLATE_SAFE &&
  						 collation == inner_cxt.collation)
  					state = FDW_COLLATE_SAFE;
  				else if (collation == DEFAULT_COLLATION_OID)
  					state = FDW_COLLATE_NONE;
  				else
  					state = FDW_COLLATE_UNSAFE;
  			}
  			break;
  		case T_List:
  			{
  				List	   *l = (List *) node;
  				ListCell   *lc;
  
  				/*
  				 * Recurse to component subexpressions.
  				 */
  				foreach(lc, l)
  				{
  					if (!foreign_expr_walker((Node *) lfirst(lc),
  											 glob_cxt, &inner_cxt))
  						return false;
  				}
  
  				/*
  				 * When processing a list, collation state just bubbles up
  				 * from the list elements.
  				 */
  				collation = inner_cxt.collation;
  				state = inner_cxt.state;
  
  				/* Don't apply exprType() to the list. */
  				check_type = false;
  			}
  			break;
  		case T_Aggref:
  			{
  				Aggref	   *agg = (Aggref *) node;
  				ListCell   *lc;
  
  				/* Not safe to pushdown when not in grouping context */
  				if (glob_cxt->foreignrel->reloptkind != RELOPT_UPPER_REL)
  					return false;
  
  				/* Only non-split aggregates are pushable. */
  				if (agg->aggsplit != AGGSPLIT_SIMPLE)
  					return false;
  
  				/* As usual, it must be shippable. */
  				if (!is_shippable(agg->aggfnoid, ProcedureRelationId, fpinfo))
  					return false;
  
  				/*
  				 * Recurse to input args. aggdirectargs, aggorder and
  				 * aggdistinct are all present in args, so no need to check
  				 * their shippability explicitly.
  				 */
  				foreach(lc, agg->args)
  				{
  					Node	   *n = (Node *) lfirst(lc);
  
  					/* If TargetEntry, extract the expression from it */
  					if (IsA(n, TargetEntry))
  					{
  						TargetEntry *tle = (TargetEntry *) n;
  
  						n = (Node *) tle->expr;
  					}
  
  					if (!foreign_expr_walker(n, glob_cxt, &inner_cxt))
  						return false;
  				}
  
  				/*
  				 * For aggorder elements, check whether the sort operator, if
  				 * specified, is shippable or not.
  				 */
  				if (agg->aggorder)
  				{
  					ListCell   *lc;
  
  					foreach(lc, agg->aggorder)
  					{
  						SortGroupClause *srt = (SortGroupClause *) lfirst(lc);
  						Oid			sortcoltype;
  						TypeCacheEntry *typentry;
  						TargetEntry *tle;
  
  						tle = get_sortgroupref_tle(srt->tleSortGroupRef,
  												   agg->args);
  						sortcoltype = exprType((Node *) tle->expr);
  						typentry = lookup_type_cache(sortcoltype,
  										TYPECACHE_LT_OPR | TYPECACHE_GT_OPR);
  						/* Check shippability of non-default sort operator. */
  						if (srt->sortop != typentry->lt_opr &&
  							srt->sortop != typentry->gt_opr &&
  							!is_shippable(srt->sortop, OperatorRelationId,
  										  fpinfo))
  							return false;
  					}
  				}
  
  				/* Check aggregate filter */
  				if (!foreign_expr_walker((Node *) agg->aggfilter,
  										 glob_cxt, &inner_cxt))
  					return false;
  
  				/*
  				 * If aggregate's input collation is not derived from a
  				 * foreign Var, it can't be sent to remote.
  				 */
  				if (agg->inputcollid == InvalidOid)
  					 /* OK, inputs are all noncollatable */ ;
  				else if (inner_cxt.state != FDW_COLLATE_SAFE ||
  						 agg->inputcollid != inner_cxt.collation)
  					return false;
  
  				/*
  				 * Detect whether node is introducing a collation not derived
  				 * from a foreign Var.  (If so, we just mark it unsafe for now
  				 * rather than immediately returning false, since the parent
  				 * node might not care.)
  				 */
  				collation = agg->aggcollid;
  				if (collation == InvalidOid)
  					state = FDW_COLLATE_NONE;
  				else if (inner_cxt.state == FDW_COLLATE_SAFE &&
  						 collation == inner_cxt.collation)
  					state = FDW_COLLATE_SAFE;
  				else if (collation == DEFAULT_COLLATION_OID)
  					state = FDW_COLLATE_NONE;
  				else
  					state = FDW_COLLATE_UNSAFE;
  			}
  			break;
  		default:
  
  			/*
  			 * If it's anything else, assume it's unsafe.  This list can be
  			 * expanded later, but don't forget to add deparse support below.
  			 */
  			return false;
  	}
  
  	/*
  	 * If result type of given expression is not shippable, it can't be sent
  	 * to remote because it might have incompatible semantics on remote side.
  	 */
  	if (check_type && !is_shippable(exprType(node), TypeRelationId, fpinfo))
  		return false;
  
  	/*
  	 * Now, merge my collation information into my parent's state.
  	 */
  	if (state > outer_cxt->state)
  	{
  		/* Override previous parent state */
  		outer_cxt->collation = collation;
  		outer_cxt->state = state;
  	}
  	else if (state == outer_cxt->state)
  	{
  		/* Merge, or detect error if there's a collation conflict */
  		switch (state)
  		{
  			case FDW_COLLATE_NONE:
  				/* Nothing + nothing is still nothing */
  				break;
  			case FDW_COLLATE_SAFE:
  				if (collation != outer_cxt->collation)
  				{
  					/*
  					 * Non-default collation always beats default.
  					 */
  					if (outer_cxt->collation == DEFAULT_COLLATION_OID)
  					{
  						/* Override previous parent state */
  						outer_cxt->collation = collation;
  					}
  					else if (collation != DEFAULT_COLLATION_OID)
  					{
  						/*
  						 * Conflict; show state as indeterminate.  We don't
  						 * want to "return false" right away, since parent
  						 * node might not care about collation.
  						 */
  						outer_cxt->state = FDW_COLLATE_UNSAFE;
  					}
  				}
  				break;
  			case FDW_COLLATE_UNSAFE:
  				/* We're still conflicted ... */
  				break;
  		}
  	}
  
  	/* It looks OK */
  	return true;
  }
  
  /*
   * Convert type OID + typmod info into a type name we can ship to the remote
   * server.  Someplace else had better have verified that this type name is
   * expected to be known on the remote end.
   *
   * This is almost just format_type_with_typemod(), except that if left to its
   * own devices, that function will make schema-qualification decisions based
   * on the local search_path, which is wrong.  We must schema-qualify all
   * type names that are not in pg_catalog.  We assume here that built-in types
   * are all in pg_catalog and need not be qualified; otherwise, qualify.
   */
  static char *
  deparse_type_name(Oid type_oid, int32 typemod)
  {
  	if (is_builtin(type_oid))
  		return format_type_with_typemod(type_oid, typemod);
  	else
  		return format_type_with_typemod_qualified(type_oid, typemod);
  }
  
  /*
   * Build the targetlist for given relation to be deparsed as SELECT clause.
   *
   * The output targetlist contains the columns that need to be fetched from the
   * foreign server for the given relation.  If foreignrel is an upper relation,
   * then the output targetlist can also contain expressions to be evaluated on
   * foreign server.
   */
  List *
  build_tlist_to_deparse(RelOptInfo *foreignrel)
  {
  	List	   *tlist = NIL;
  	PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) foreignrel->fdw_private;
  
  	/*
  	 * For an upper relation, we have already built the target list while
  	 * checking shippability, so just return that.
  	 */
  	if (foreignrel->reloptkind == RELOPT_UPPER_REL)
  		return fpinfo->grouped_tlist;
  
  	/*
  	 * We require columns specified in foreignrel->reltarget->exprs and those
  	 * required for evaluating the local conditions.
  	 */
  	tlist = add_to_flat_tlist(tlist,
  					   pull_var_clause((Node *) foreignrel->reltarget->exprs,
  									   PVC_RECURSE_PLACEHOLDERS));
  	tlist = add_to_flat_tlist(tlist,
  							  pull_var_clause((Node *) fpinfo->local_conds,
  											  PVC_RECURSE_PLACEHOLDERS));
  
  	return tlist;
  }
  
  /*
   * Deparse SELECT statement for given relation into buf.
   *
   * tlist contains the list of desired columns to be fetched from foreign server.
   * For a base relation fpinfo->attrs_used is used to construct SELECT clause,
   * hence the tlist is ignored for a base relation.
   *
   * remote_conds is the list of conditions to be deparsed into the WHERE clause
   * (or, in the case of upper relations, into the HAVING clause).
   *
   * If params_list is not NULL, it receives a list of Params and other-relation
   * Vars used in the clauses; these values must be transmitted to the remote
   * server as parameter values.
   *
   * If params_list is NULL, we're generating the query for EXPLAIN purposes,
   * so Params and other-relation Vars should be replaced by dummy values.
   *
   * pathkeys is the list of pathkeys to order the result by.
   *
   * List of columns selected is returned in retrieved_attrs.
   */
  extern void
  deparseSelectStmtForRel(StringInfo buf, PlannerInfo *root, RelOptInfo *rel,
  						List *tlist, List *remote_conds, List *pathkeys,
  						List **retrieved_attrs, List **params_list)
  {
  	deparse_expr_cxt context;
  	PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) rel->fdw_private;
  	List	   *quals;
  
  	/*
  	 * We handle relations for foreign tables, joins between those and upper
  	 * relations.
  	 */
  	Assert(rel->reloptkind == RELOPT_JOINREL ||
  		   rel->reloptkind == RELOPT_BASEREL ||
  		   rel->reloptkind == RELOPT_OTHER_MEMBER_REL ||
  		   rel->reloptkind == RELOPT_UPPER_REL);
  
  	/* Fill portions of context common to upper, join and base relation */
  	context.buf = buf;
  	context.root = root;
  	context.foreignrel = rel;
  	context.scanrel = (rel->reloptkind == RELOPT_UPPER_REL) ?
  		fpinfo->outerrel : rel;
  	context.params_list = params_list;
  
  	/* Construct SELECT clause */
  	deparseSelectSql(tlist, retrieved_attrs, &context);
  
  	/*
  	 * For upper relations, the WHERE clause is built from the remote
  	 * conditions of the underlying scan relation; otherwise, we can use the
  	 * supplied list of remote conditions directly.
  	 */
  	if (rel->reloptkind == RELOPT_UPPER_REL)
  	{
  		PgFdwRelationInfo *ofpinfo;
  
  		ofpinfo = (PgFdwRelationInfo *) fpinfo->outerrel->fdw_private;
  		quals = ofpinfo->remote_conds;
  	}
  	else
  		quals = remote_conds;
  
  	/* Construct FROM and WHERE clauses */
  	deparseFromExpr(quals, &context);
  
  	if (rel->reloptkind == RELOPT_UPPER_REL)
  	{
  		/* Append GROUP BY clause */
  		appendGroupByClause(tlist, &context);
  
  		/* Append HAVING clause */
  		if (remote_conds)
  		{
  			appendStringInfo(buf, " HAVING ");
  			appendConditions(remote_conds, &context);
  		}
  	}
  
  	/* Add ORDER BY clause if we found any useful pathkeys */
  	if (pathkeys)
  		appendOrderByClause(pathkeys, &context);
  
  	/* Add any necessary FOR UPDATE/SHARE. */
  	deparseLockingClause(&context);
  }
  
  /*
   * Construct a simple SELECT statement that retrieves desired columns
   * of the specified foreign table, and append it to "buf".  The output
   * contains just "SELECT ... ".
   *
   * We also create an integer List of the columns being retrieved, which is
   * returned to *retrieved_attrs.
   *
   * tlist is the list of desired columns. Read prologue of
   * deparseSelectStmtForRel() for details.
   */
  static void
  deparseSelectSql(List *tlist, List **retrieved_attrs, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	RelOptInfo *foreignrel = context->foreignrel;
  	PlannerInfo *root = context->root;
  	PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) foreignrel->fdw_private;
  
  	/*
  	 * Construct SELECT list
  	 */
  	appendStringInfoString(buf, "SELECT ");
  
  	if (foreignrel->reloptkind == RELOPT_JOINREL ||
  		foreignrel->reloptkind == RELOPT_UPPER_REL)
  	{
  		/* For a join relation use the input tlist */
  		deparseExplicitTargetList(tlist, retrieved_attrs, context);
  	}
  	else
  	{
  		/*
  		 * For a base relation fpinfo->attrs_used gives the list of columns
  		 * required to be fetched from the foreign server.
  		 */
  		RangeTblEntry *rte = planner_rt_fetch(foreignrel->relid, root);
  
  		/*
  		 * Core code already has some lock on each rel being planned, so we
  		 * can use NoLock here.
  		 */
  		Relation	rel = heap_open(rte->relid, NoLock);
  
  		deparseTargetList(buf, root, foreignrel->relid, rel, false,
  						  fpinfo->attrs_used, false, retrieved_attrs);
  		heap_close(rel, NoLock);
  	}
  }
  
  /*
   * Construct a FROM clause and, if needed, a WHERE clause, and append those to
   * "buf".
   *
   * quals is the list of clauses to be included in the WHERE clause.
   */
  static void
  deparseFromExpr(List *quals, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	RelOptInfo *scanrel = context->scanrel;
  
  	/* For upper relations, scanrel must be either a joinrel or a baserel */
  	Assert(context->foreignrel->reloptkind != RELOPT_UPPER_REL ||
  		   scanrel->reloptkind == RELOPT_JOINREL ||
  		   scanrel->reloptkind == RELOPT_BASEREL);
  
  	/* Construct FROM clause */
  	appendStringInfoString(buf, " FROM ");
  	deparseFromExprForRel(buf, context->root, scanrel,
  						  (bms_num_members(scanrel->relids) > 1),
  						  context->params_list);
  
  	/* Construct WHERE clause */
  	if (quals != NIL)
  	{
  		appendStringInfo(buf, " WHERE ");
  		appendConditions(quals, context);
  	}
  }
  
  /*
   * Emit a target list that retrieves the columns specified in attrs_used.
   * This is used for both SELECT and RETURNING targetlists; the is_returning
   * parameter is true only for a RETURNING targetlist.
   *
   * The tlist text is appended to buf, and we also create an integer List
   * of the columns being retrieved, which is returned to *retrieved_attrs.
   *
   * If qualify_col is true, add relation alias before the column name.
   */
  static void
  deparseTargetList(StringInfo buf,
  				  PlannerInfo *root,
  				  Index rtindex,
  				  Relation rel,
  				  bool is_returning,
  				  Bitmapset *attrs_used,
  				  bool qualify_col,
  				  List **retrieved_attrs)
  {
  	TupleDesc	tupdesc = RelationGetDescr(rel);
  	bool		have_wholerow;
  	bool		first;
  	int			i;
  
  	*retrieved_attrs = NIL;
  
  	/* If there's a whole-row reference, we'll need all the columns. */
  	have_wholerow = bms_is_member(0 - FirstLowInvalidHeapAttributeNumber,
  								  attrs_used);
  
  	first = true;
  	for (i = 1; i <= tupdesc->natts; i++)
  	{
  		Form_pg_attribute attr = tupdesc->attrs[i - 1];
  
  		/* Ignore dropped attributes. */
  		if (attr->attisdropped)
  			continue;
  
  		if (have_wholerow ||
  			bms_is_member(i - FirstLowInvalidHeapAttributeNumber,
  						  attrs_used))
  		{
  			if (!first)
  				appendStringInfoString(buf, ", ");
  			else if (is_returning)
  				appendStringInfoString(buf, " RETURNING ");
  			first = false;
  
  			deparseColumnRef(buf, rtindex, i, root, qualify_col);
  
  			*retrieved_attrs = lappend_int(*retrieved_attrs, i);
  		}
  	}
  
  	/*
  	 * Add ctid and oid if needed.  We currently don't support retrieving any
  	 * other system columns.
  	 */
  	if (bms_is_member(SelfItemPointerAttributeNumber - FirstLowInvalidHeapAttributeNumber,
  					  attrs_used))
  	{
  		if (!first)
  			appendStringInfoString(buf, ", ");
  		else if (is_returning)
  			appendStringInfoString(buf, " RETURNING ");
  		first = false;
  
  		if (qualify_col)
  			ADD_REL_QUALIFIER(buf, rtindex);
  		appendStringInfoString(buf, "ctid");
  
  		*retrieved_attrs = lappend_int(*retrieved_attrs,
  									   SelfItemPointerAttributeNumber);
  	}
  	if (bms_is_member(ObjectIdAttributeNumber - FirstLowInvalidHeapAttributeNumber,
  					  attrs_used))
  	{
  		if (!first)
  			appendStringInfoString(buf, ", ");
  		else if (is_returning)
  			appendStringInfoString(buf, " RETURNING ");
  		first = false;
  
  		if (qualify_col)
  			ADD_REL_QUALIFIER(buf, rtindex);
  		appendStringInfoString(buf, "oid");
  
  		*retrieved_attrs = lappend_int(*retrieved_attrs,
  									   ObjectIdAttributeNumber);
  	}
  
  	/* Don't generate bad syntax if no undropped columns */
  	if (first && !is_returning)
  		appendStringInfoString(buf, "NULL");
  }
  
  /*
   * Deparse the appropriate locking clause (FOR UPDATE or FOR SHARE) for a
   * given relation (context->scanrel).
   */
  static void
  deparseLockingClause(deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	PlannerInfo *root = context->root;
  	RelOptInfo *rel = context->scanrel;
  	int			relid = -1;
  
  	while ((relid = bms_next_member(rel->relids, relid)) >= 0)
  	{
  		/*
  		 * Add FOR UPDATE/SHARE if appropriate.  We apply locking during the
  		 * initial row fetch, rather than later on as is done for local
  		 * tables. The extra roundtrips involved in trying to duplicate the
  		 * local semantics exactly don't seem worthwhile (see also comments
  		 * for RowMarkType).
  		 *
  		 * Note: because we actually run the query as a cursor, this assumes
  		 * that DECLARE CURSOR ... FOR UPDATE is supported, which it isn't
  		 * before 8.3.
  		 */
  		if (relid == root->parse->resultRelation &&
  			(root->parse->commandType == CMD_UPDATE ||
  			 root->parse->commandType == CMD_DELETE))
  		{
  			/* Relation is UPDATE/DELETE target, so use FOR UPDATE */
  			appendStringInfoString(buf, " FOR UPDATE");
  
  			/* Add the relation alias if we are here for a join relation */
  			if (rel->reloptkind == RELOPT_JOINREL)
  				appendStringInfo(buf, " OF %s%d", REL_ALIAS_PREFIX, relid);
  		}
  		else
  		{
  			PlanRowMark *rc = get_plan_rowmark(root->rowMarks, relid);
  
  			if (rc)
  			{
  				/*
  				 * Relation is specified as a FOR UPDATE/SHARE target, so
  				 * handle that.  (But we could also see LCS_NONE, meaning this
  				 * isn't a target relation after all.)
  				 *
  				 * For now, just ignore any [NO] KEY specification, since (a)
  				 * it's not clear what that means for a remote table that we
  				 * don't have complete information about, and (b) it wouldn't
  				 * work anyway on older remote servers.  Likewise, we don't
  				 * worry about NOWAIT.
  				 */
  				switch (rc->strength)
  				{
  					case LCS_NONE:
  						/* No locking needed */
  						break;
  					case LCS_FORKEYSHARE:
  					case LCS_FORSHARE:
  						appendStringInfoString(buf, " FOR SHARE");
  						break;
  					case LCS_FORNOKEYUPDATE:
  					case LCS_FORUPDATE:
  						appendStringInfoString(buf, " FOR UPDATE");
  						break;
  				}
  
  				/* Add the relation alias if we are here for a join relation */
  				if (bms_num_members(rel->relids) > 1 &&
  					rc->strength != LCS_NONE)
  					appendStringInfo(buf, " OF %s%d", REL_ALIAS_PREFIX, relid);
  			}
  		}
  	}
  }
  
  /*
   * Deparse conditions from the provided list and append them to buf.
   *
   * The conditions in the list are assumed to be ANDed. This function is used to
   * deparse WHERE clauses, JOIN .. ON clauses and HAVING clauses.
   */
  static void
  appendConditions(List *exprs, deparse_expr_cxt *context)
  {
  	int			nestlevel;
  	ListCell   *lc;
  	bool		is_first = true;
  	StringInfo	buf = context->buf;
  
  	/* Make sure any constants in the exprs are printed portably */
  	nestlevel = set_transmission_modes();
  
  	foreach(lc, exprs)
  	{
  		Expr	   *expr = (Expr *) lfirst(lc);
  
  		/*
  		 * Extract clause from RestrictInfo, if required. See comments in
  		 * declaration of PgFdwRelationInfo for details.
  		 */
  		if (IsA(expr, RestrictInfo))
  		{
  			RestrictInfo *ri = (RestrictInfo *) expr;
  
  			expr = ri->clause;
  		}
  
  		/* Connect expressions with "AND" and parenthesize each condition. */
  		if (!is_first)
  			appendStringInfoString(buf, " AND ");
  
  		appendStringInfoChar(buf, '(');
  		deparseExpr(expr, context);
  		appendStringInfoChar(buf, ')');
  
  		is_first = false;
  	}
  
  	reset_transmission_modes(nestlevel);
  }
  
  /* Output join name for given join type */
  extern const char *
  get_jointype_name(JoinType jointype)
  {
  	switch (jointype)
  	{
  		case JOIN_INNER:
  			return "INNER";
  
  		case JOIN_LEFT:
  			return "LEFT";
  
  		case JOIN_RIGHT:
  			return "RIGHT";
  
  		case JOIN_FULL:
  			return "FULL";
  
  		default:
  			/* Shouldn't come here, but protect from buggy code. */
  			elog(ERROR, "unsupported join type %d", jointype);
  	}
  
  	/* Keep compiler happy */
  	return NULL;
  }
  
  /*
   * Deparse given targetlist and append it to context->buf.
   *
   * tlist is list of TargetEntry's which in turn contain Var nodes.
   *
   * retrieved_attrs is the list of continuously increasing integers starting
   * from 1. It has same number of entries as tlist.
   */
  static void
  deparseExplicitTargetList(List *tlist, List **retrieved_attrs,
  						  deparse_expr_cxt *context)
  {
  	ListCell   *lc;
  	StringInfo	buf = context->buf;
  	int			i = 0;
  
  	*retrieved_attrs = NIL;
  
  	foreach(lc, tlist)
  	{
  		TargetEntry *tle = (TargetEntry *) lfirst(lc);
  
  		/* Extract expression if TargetEntry node */
  		Assert(IsA(tle, TargetEntry));
  
  		if (i > 0)
  			appendStringInfoString(buf, ", ");
  		deparseExpr((Expr *) tle->expr, context);
  
  		*retrieved_attrs = lappend_int(*retrieved_attrs, i + 1);
  		i++;
  	}
  
  	if (i == 0)
  		appendStringInfoString(buf, "NULL");
  }
  
  /*
   * Construct FROM clause for given relation
   *
   * The function constructs ... JOIN ... ON ... for join relation. For a base
   * relation it just returns schema-qualified tablename, with the appropriate
   * alias if so requested.
   */
  static void
  deparseFromExprForRel(StringInfo buf, PlannerInfo *root, RelOptInfo *foreignrel,
  					  bool use_alias, List **params_list)
  {
  	PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) foreignrel->fdw_private;
  
  	if (foreignrel->reloptkind == RELOPT_JOINREL)
  	{
  		RelOptInfo *rel_o = fpinfo->outerrel;
  		RelOptInfo *rel_i = fpinfo->innerrel;
  		StringInfoData join_sql_o;
  		StringInfoData join_sql_i;
  
  		/* Deparse outer relation */
  		initStringInfo(&join_sql_o);
  		deparseFromExprForRel(&join_sql_o, root, rel_o, true, params_list);
  
  		/* Deparse inner relation */
  		initStringInfo(&join_sql_i);
  		deparseFromExprForRel(&join_sql_i, root, rel_i, true, params_list);
  
  		/*
  		 * For a join relation FROM clause entry is deparsed as
  		 *
  		 * ((outer relation) <join type> (inner relation) ON (joinclauses))
  		 */
  		appendStringInfo(buf, "(%s %s JOIN %s ON ", join_sql_o.data,
  					   get_jointype_name(fpinfo->jointype), join_sql_i.data);
  
  		/* Append join clause; (TRUE) if no join clause */
  		if (fpinfo->joinclauses)
  		{
  			deparse_expr_cxt context;
  
  			context.buf = buf;
  			context.foreignrel = foreignrel;
  			context.scanrel = foreignrel;
  			context.root = root;
  			context.params_list = params_list;
  
  			appendStringInfo(buf, "(");
  			appendConditions(fpinfo->joinclauses, &context);
  			appendStringInfo(buf, ")");
  		}
  		else
  			appendStringInfoString(buf, "(TRUE)");
  
  		/* End the FROM clause entry. */
  		appendStringInfo(buf, ")");
  	}
  	else
  	{
  		RangeTblEntry *rte = planner_rt_fetch(foreignrel->relid, root);
  
  		/*
  		 * Core code already has some lock on each rel being planned, so we
  		 * can use NoLock here.
  		 */
  		Relation	rel = heap_open(rte->relid, NoLock);
  
  		deparseRelation(buf, rel);
  
  		/*
  		 * Add a unique alias to avoid any conflict in relation names due to
  		 * pulled up subqueries in the query being built for a pushed down
  		 * join.
  		 */
  		if (use_alias)
  			appendStringInfo(buf, " %s%d", REL_ALIAS_PREFIX, foreignrel->relid);
  
  		heap_close(rel, NoLock);
  	}
  }
  
  /*
   * deparse remote INSERT statement
   *
   * The statement text is appended to buf, and we also create an integer List
   * of the columns being retrieved by RETURNING (if any), which is returned
   * to *retrieved_attrs.
   */
  void
  deparseInsertSql(StringInfo buf, PlannerInfo *root,
  				 Index rtindex, Relation rel,
  				 List *targetAttrs, bool doNothing,
  				 List *returningList, List **retrieved_attrs)
  {
  	AttrNumber	pindex;
  	bool		first;
  	ListCell   *lc;
  
  	appendStringInfoString(buf, "INSERT INTO ");
  	deparseRelation(buf, rel);
  
  	if (targetAttrs)
  	{
  		appendStringInfoChar(buf, '(');
  
  		first = true;
  		foreach(lc, targetAttrs)
  		{
  			int			attnum = lfirst_int(lc);
  
  			if (!first)
  				appendStringInfoString(buf, ", ");
  			first = false;
  
  			deparseColumnRef(buf, rtindex, attnum, root, false);
  		}
  
  		appendStringInfoString(buf, ") VALUES (");
  
  		pindex = 1;
  		first = true;
  		foreach(lc, targetAttrs)
  		{
  			if (!first)
  				appendStringInfoString(buf, ", ");
  			first = false;
  
  			appendStringInfo(buf, "$%d", pindex);
  			pindex++;
  		}
  
  		appendStringInfoChar(buf, ')');
  	}
  	else
  		appendStringInfoString(buf, " DEFAULT VALUES");
  
  	if (doNothing)
  		appendStringInfoString(buf, " ON CONFLICT DO NOTHING");
  
  	deparseReturningList(buf, root, rtindex, rel,
  					   rel->trigdesc && rel->trigdesc->trig_insert_after_row,
  						 returningList, retrieved_attrs);
  }
  
  /*
   * deparse remote UPDATE statement
   *
   * The statement text is appended to buf, and we also create an integer List
   * of the columns being retrieved by RETURNING (if any), which is returned
   * to *retrieved_attrs.
   */
  void
  deparseUpdateSql(StringInfo buf, PlannerInfo *root,
  				 Index rtindex, Relation rel,
  				 List *targetAttrs, List *returningList,
  				 List **retrieved_attrs)
  {
  	AttrNumber	pindex;
  	bool		first;
  	ListCell   *lc;
  
  	appendStringInfoString(buf, "UPDATE ");
  	deparseRelation(buf, rel);
  	appendStringInfoString(buf, " SET ");
  
  	pindex = 2;					/* ctid is always the first param */
  	first = true;
  	foreach(lc, targetAttrs)
  	{
  		int			attnum = lfirst_int(lc);
  
  		if (!first)
  			appendStringInfoString(buf, ", ");
  		first = false;
  
  		deparseColumnRef(buf, rtindex, attnum, root, false);
  		appendStringInfo(buf, " = $%d", pindex);
  		pindex++;
  	}
  	appendStringInfoString(buf, " WHERE ctid = $1");
  
  	deparseReturningList(buf, root, rtindex, rel,
  					   rel->trigdesc && rel->trigdesc->trig_update_after_row,
  						 returningList, retrieved_attrs);
  }
  
  /*
   * deparse remote UPDATE statement
   *
   * The statement text is appended to buf, and we also create an integer List
   * of the columns being retrieved by RETURNING (if any), which is returned
   * to *retrieved_attrs.
   */
  void
  deparseDirectUpdateSql(StringInfo buf, PlannerInfo *root,
  					   Index rtindex, Relation rel,
  					   List *targetlist,
  					   List *targetAttrs,
  					   List *remote_conds,
  					   List **params_list,
  					   List *returningList,
  					   List **retrieved_attrs)
  {
  	RelOptInfo *baserel = root->simple_rel_array[rtindex];
  	deparse_expr_cxt context;
  	int			nestlevel;
  	bool		first;
  	ListCell   *lc;
  
  	/* Set up context struct for recursion */
  	context.root = root;
  	context.foreignrel = baserel;
  	context.scanrel = baserel;
  	context.buf = buf;
  	context.params_list = params_list;
  
  	appendStringInfoString(buf, "UPDATE ");
  	deparseRelation(buf, rel);
  	appendStringInfoString(buf, " SET ");
  
  	/* Make sure any constants in the exprs are printed portably */
  	nestlevel = set_transmission_modes();
  
  	first = true;
  	foreach(lc, targetAttrs)
  	{
  		int			attnum = lfirst_int(lc);
  		TargetEntry *tle = get_tle_by_resno(targetlist, attnum);
  
  		if (!tle)
  			elog(ERROR, "attribute number %d not found in UPDATE targetlist",
  				 attnum);
  
  		if (!first)
  			appendStringInfoString(buf, ", ");
  		first = false;
  
  		deparseColumnRef(buf, rtindex, attnum, root, false);
  		appendStringInfoString(buf, " = ");
  		deparseExpr((Expr *) tle->expr, &context);
  	}
  
  	reset_transmission_modes(nestlevel);
  
  	if (remote_conds)
  	{
  		appendStringInfo(buf, " WHERE ");
  		appendConditions(remote_conds, &context);
  	}
  
  	deparseReturningList(buf, root, rtindex, rel, false,
  						 returningList, retrieved_attrs);
  }
  
  /*
   * deparse remote DELETE statement
   *
   * The statement text is appended to buf, and we also create an integer List
   * of the columns being retrieved by RETURNING (if any), which is returned
   * to *retrieved_attrs.
   */
  void
  deparseDeleteSql(StringInfo buf, PlannerInfo *root,
  				 Index rtindex, Relation rel,
  				 List *returningList,
  				 List **retrieved_attrs)
  {
  	appendStringInfoString(buf, "DELETE FROM ");
  	deparseRelation(buf, rel);
  	appendStringInfoString(buf, " WHERE ctid = $1");
  
  	deparseReturningList(buf, root, rtindex, rel,
  					   rel->trigdesc && rel->trigdesc->trig_delete_after_row,
  						 returningList, retrieved_attrs);
  }
  
  /*
   * deparse remote DELETE statement
   *
   * The statement text is appended to buf, and we also create an integer List
   * of the columns being retrieved by RETURNING (if any), which is returned
   * to *retrieved_attrs.
   */
  void
  deparseDirectDeleteSql(StringInfo buf, PlannerInfo *root,
  					   Index rtindex, Relation rel,
  					   List *remote_conds,
  					   List **params_list,
  					   List *returningList,
  					   List **retrieved_attrs)
  {
  	RelOptInfo *baserel = root->simple_rel_array[rtindex];
  	deparse_expr_cxt context;
  
  	/* Set up context struct for recursion */
  	context.root = root;
  	context.foreignrel = baserel;
  	context.scanrel = baserel;
  	context.buf = buf;
  	context.params_list = params_list;
  
  	appendStringInfoString(buf, "DELETE FROM ");
  	deparseRelation(buf, rel);
  
  	if (remote_conds)
  	{
  		appendStringInfo(buf, " WHERE ");
  		appendConditions(remote_conds, &context);
  	}
  
  	deparseReturningList(buf, root, rtindex, rel, false,
  						 returningList, retrieved_attrs);
  }
  
  /*
   * Add a RETURNING clause, if needed, to an INSERT/UPDATE/DELETE.
   */
  static void
  deparseReturningList(StringInfo buf, PlannerInfo *root,
  					 Index rtindex, Relation rel,
  					 bool trig_after_row,
  					 List *returningList,
  					 List **retrieved_attrs)
  {
  	Bitmapset  *attrs_used = NULL;
  
  	if (trig_after_row)
  	{
  		/* whole-row reference acquires all non-system columns */
  		attrs_used =
  			bms_make_singleton(0 - FirstLowInvalidHeapAttributeNumber);
  	}
  
  	if (returningList != NIL)
  	{
  		/*
  		 * We need the attrs, non-system and system, mentioned in the local
  		 * query's RETURNING list.
  		 */
  		pull_varattnos((Node *) returningList, rtindex,
  					   &attrs_used);
  	}
  
  	if (attrs_used != NULL)
  		deparseTargetList(buf, root, rtindex, rel, true, attrs_used, false,
  						  retrieved_attrs);
  	else
  		*retrieved_attrs = NIL;
  }
  
  /*
   * Construct SELECT statement to acquire size in blocks of given relation.
   *
   * Note: we use local definition of block size, not remote definition.
   * This is perhaps debatable.
   *
   * Note: pg_relation_size() exists in 8.1 and later.
   */
  void
  deparseAnalyzeSizeSql(StringInfo buf, Relation rel)
  {
  	StringInfoData relname;
  
  	/* We'll need the remote relation name as a literal. */
  	initStringInfo(&relname);
  	deparseRelation(&relname, rel);
  
  	appendStringInfoString(buf, "SELECT pg_catalog.pg_relation_size(");
  	deparseStringLiteral(buf, relname.data);
  	appendStringInfo(buf, "::pg_catalog.regclass) / %d", BLCKSZ);
  }
  
  /*
   * Construct SELECT statement to acquire sample rows of given relation.
   *
   * SELECT command is appended to buf, and list of columns retrieved
   * is returned to *retrieved_attrs.
   */
  void
  deparseAnalyzeSql(StringInfo buf, Relation rel, List **retrieved_attrs)
  {
  	Oid			relid = RelationGetRelid(rel);
  	TupleDesc	tupdesc = RelationGetDescr(rel);
  	int			i;
  	char	   *colname;
  	List	   *options;
  	ListCell   *lc;
  	bool		first = true;
  
  	*retrieved_attrs = NIL;
  
  	appendStringInfoString(buf, "SELECT ");
  	for (i = 0; i < tupdesc->natts; i++)
  	{
  		/* Ignore dropped columns. */
  		if (tupdesc->attrs[i]->attisdropped)
  			continue;
  
  		if (!first)
  			appendStringInfoString(buf, ", ");
  		first = false;
  
  		/* Use attribute name or column_name option. */
  		colname = NameStr(tupdesc->attrs[i]->attname);
  		options = GetForeignColumnOptions(relid, i + 1);
  
  		foreach(lc, options)
  		{
  			DefElem    *def = (DefElem *) lfirst(lc);
  
  			if (strcmp(def->defname, "column_name") == 0)
  			{
  				colname = defGetString(def);
  				break;
  			}
  		}
  
  		appendStringInfoString(buf, quote_identifier(colname));
  
  		*retrieved_attrs = lappend_int(*retrieved_attrs, i + 1);
  	}
  
  	/* Don't generate bad syntax for zero-column relation. */
  	if (first)
  		appendStringInfoString(buf, "NULL");
  
  	/*
  	 * Construct FROM clause
  	 */
  	appendStringInfoString(buf, " FROM ");
  	deparseRelation(buf, rel);
  }
  
  /*
   * Construct name to use for given column, and emit it into buf.
   * If it has a column_name FDW option, use that instead of attribute name.
   *
   * If qualify_col is true, qualify column name with the alias of relation.
   */
  static void
  deparseColumnRef(StringInfo buf, int varno, int varattno, PlannerInfo *root,
  				 bool qualify_col)
  {
  	RangeTblEntry *rte;
  
  	/* We support fetching the remote side's CTID and OID. */
  	if (varattno == SelfItemPointerAttributeNumber)
  	{
  		if (qualify_col)
  			ADD_REL_QUALIFIER(buf, varno);
  		appendStringInfoString(buf, "ctid");
  	}
  	else if (varattno == ObjectIdAttributeNumber)
  	{
  		if (qualify_col)
  			ADD_REL_QUALIFIER(buf, varno);
  		appendStringInfoString(buf, "oid");
  	}
  	else if (varattno < 0)
  	{
  		/*
  		 * All other system attributes are fetched as 0, except for table OID,
  		 * which is fetched as the local table OID.  However, we must be
  		 * careful; the table could be beneath an outer join, in which case it
  		 * must go to NULL whenever the rest of the row does.
  		 */
  		Oid			fetchval = 0;
  
  		if (varattno == TableOidAttributeNumber)
  		{
  			rte = planner_rt_fetch(varno, root);
  			fetchval = rte->relid;
  		}
  
  		if (qualify_col)
  		{
  			appendStringInfoString(buf, "CASE WHEN (");
  			ADD_REL_QUALIFIER(buf, varno);
  			appendStringInfo(buf, "*)::text IS NOT NULL THEN %u END", fetchval);
  		}
  		else
  			appendStringInfo(buf, "%u", fetchval);
  	}
  	else if (varattno == 0)
  	{
  		/* Whole row reference */
  		Relation	rel;
  		Bitmapset  *attrs_used;
  
  		/* Required only to be passed down to deparseTargetList(). */
  		List	   *retrieved_attrs;
  
  		/* Get RangeTblEntry from array in PlannerInfo. */
  		rte = planner_rt_fetch(varno, root);
  
  		/*
  		 * The lock on the relation will be held by upper callers, so it's
  		 * fine to open it with no lock here.
  		 */
  		rel = heap_open(rte->relid, NoLock);
  
  		/*
  		 * The local name of the foreign table can not be recognized by the
  		 * foreign server and the table it references on foreign server might
  		 * have different column ordering or different columns than those
  		 * declared locally. Hence we have to deparse whole-row reference as
  		 * ROW(columns referenced locally). Construct this by deparsing a
  		 * "whole row" attribute.
  		 */
  		attrs_used = bms_add_member(NULL,
  									0 - FirstLowInvalidHeapAttributeNumber);
  
  		/*
  		 * In case the whole-row reference is under an outer join then it has
  		 * to go NULL whenever the rest of the row goes NULL. Deparsing a join
  		 * query would always involve multiple relations, thus qualify_col
  		 * would be true.
  		 */
  		if (qualify_col)
  		{
  			appendStringInfoString(buf, "CASE WHEN (");
  			ADD_REL_QUALIFIER(buf, varno);
  			appendStringInfo(buf, "*)::text IS NOT NULL THEN ");
  		}
  
  		appendStringInfoString(buf, "ROW(");
  		deparseTargetList(buf, root, varno, rel, false, attrs_used, qualify_col,
  						  &retrieved_attrs);
  		appendStringInfoString(buf, ")");
  
  		/* Complete the CASE WHEN statement started above. */
  		if (qualify_col)
  			appendStringInfo(buf, " END");
  
  		heap_close(rel, NoLock);
  		bms_free(attrs_used);
  	}
  	else
  	{
  		char	   *colname = NULL;
  		List	   *options;
  		ListCell   *lc;
  
  		/* varno must not be any of OUTER_VAR, INNER_VAR and INDEX_VAR. */
  		Assert(!IS_SPECIAL_VARNO(varno));
  
  		/* Get RangeTblEntry from array in PlannerInfo. */
  		rte = planner_rt_fetch(varno, root);
  
  		/*
  		 * If it's a column of a foreign table, and it has the column_name FDW
  		 * option, use that value.
  		 */
  		options = GetForeignColumnOptions(rte->relid, varattno);
  		foreach(lc, options)
  		{
  			DefElem    *def = (DefElem *) lfirst(lc);
  
  			if (strcmp(def->defname, "column_name") == 0)
  			{
  				colname = defGetString(def);
  				break;
  			}
  		}
  
  		/*
  		 * If it's a column of a regular table or it doesn't have column_name
  		 * FDW option, use attribute name.
  		 */
  		if (colname == NULL)
  			colname = get_relid_attribute_name(rte->relid, varattno);
  
  		if (qualify_col)
  			ADD_REL_QUALIFIER(buf, varno);
  
  		appendStringInfoString(buf, quote_identifier(colname));
  	}
  }
  
  /*
   * Append remote name of specified foreign table to buf.
   * Use value of table_name FDW option (if any) instead of relation's name.
   * Similarly, schema_name FDW option overrides schema name.
   */
  static void
  deparseRelation(StringInfo buf, Relation rel)
  {
  	ForeignTable *table;
  	const char *nspname = NULL;
  	const char *relname = NULL;
  	ListCell   *lc;
  
  	/* obtain additional catalog information. */
  	table = GetForeignTable(RelationGetRelid(rel));
  
  	/*
  	 * Use value of FDW options if any, instead of the name of object itself.
  	 */
  	foreach(lc, table->options)
  	{
  		DefElem    *def = (DefElem *) lfirst(lc);
  
  		if (strcmp(def->defname, "schema_name") == 0)
  			nspname = defGetString(def);
  		else if (strcmp(def->defname, "table_name") == 0)
  			relname = defGetString(def);
  	}
  
  	/*
  	 * Note: we could skip printing the schema name if it's pg_catalog, but
  	 * that doesn't seem worth the trouble.
  	 */
  	if (nspname == NULL)
  		nspname = get_namespace_name(RelationGetNamespace(rel));
  	if (relname == NULL)
  		relname = RelationGetRelationName(rel);
  
  	appendStringInfo(buf, "%s.%s",
  					 quote_identifier(nspname), quote_identifier(relname));
  }
  
  /*
   * Append a SQL string literal representing "val" to buf.
   */
  void
  deparseStringLiteral(StringInfo buf, const char *val)
  {
  	const char *valptr;
  
  	/*
  	 * Rather than making assumptions about the remote server's value of
  	 * standard_conforming_strings, always use E'foo' syntax if there are any
  	 * backslashes.  This will fail on remote servers before 8.1, but those
  	 * are long out of support.
  	 */
  	if (strchr(val, '\\') != NULL)
  		appendStringInfoChar(buf, ESCAPE_STRING_SYNTAX);
  	appendStringInfoChar(buf, '\'');
  	for (valptr = val; *valptr; valptr++)
  	{
  		char		ch = *valptr;
  
  		if (SQL_STR_DOUBLE(ch, true))
  			appendStringInfoChar(buf, ch);
  		appendStringInfoChar(buf, ch);
  	}
  	appendStringInfoChar(buf, '\'');
  }
  
  /*
   * Deparse given expression into context->buf.
   *
   * This function must support all the same node types that foreign_expr_walker
   * accepts.
   *
   * Note: unlike ruleutils.c, we just use a simple hard-wired parenthesization
   * scheme: anything more complex than a Var, Const, function call or cast
   * should be self-parenthesized.
   */
  static void
  deparseExpr(Expr *node, deparse_expr_cxt *context)
  {
  	if (node == NULL)
  		return;
  
  	switch (nodeTag(node))
  	{
  		case T_Var:
  			deparseVar((Var *) node, context);
  			break;
  		case T_Const:
  			deparseConst((Const *) node, context, 0);
  			break;
  		case T_Param:
  			deparseParam((Param *) node, context);
  			break;
  		case T_ArrayRef:
  			deparseArrayRef((ArrayRef *) node, context);
  			break;
  		case T_FuncExpr:
  			deparseFuncExpr((FuncExpr *) node, context);
  			break;
  		case T_OpExpr:
  			deparseOpExpr((OpExpr *) node, context);
  			break;
  		case T_DistinctExpr:
  			deparseDistinctExpr((DistinctExpr *) node, context);
  			break;
  		case T_ScalarArrayOpExpr:
  			deparseScalarArrayOpExpr((ScalarArrayOpExpr *) node, context);
  			break;
  		case T_RelabelType:
  			deparseRelabelType((RelabelType *) node, context);
  			break;
  		case T_BoolExpr:
  			deparseBoolExpr((BoolExpr *) node, context);
  			break;
  		case T_NullTest:
  			deparseNullTest((NullTest *) node, context);
  			break;
  		case T_ArrayExpr:
  			deparseArrayExpr((ArrayExpr *) node, context);
  			break;
  		case T_Aggref:
  			deparseAggref((Aggref *) node, context);
  			break;
  		default:
  			elog(ERROR, "unsupported expression type for deparse: %d",
  				 (int) nodeTag(node));
  			break;
  	}
  }
  
  /*
   * Deparse given Var node into context->buf.
   *
   * If the Var belongs to the foreign relation, just print its remote name.
   * Otherwise, it's effectively a Param (and will in fact be a Param at
   * run time).  Handle it the same way we handle plain Params --- see
   * deparseParam for comments.
   */
  static void
  deparseVar(Var *node, deparse_expr_cxt *context)
  {
  	Relids		relids = context->scanrel->relids;
  
  	/* Qualify columns when multiple relations are involved. */
  	bool		qualify_col = (bms_num_members(relids) > 1);
  
  	if (bms_is_member(node->varno, relids) && node->varlevelsup == 0)
  		deparseColumnRef(context->buf, node->varno, node->varattno,
  						 context->root, qualify_col);
  	else
  	{
  		/* Treat like a Param */
  		if (context->params_list)
  		{
  			int			pindex = 0;
  			ListCell   *lc;
  
  			/* find its index in params_list */
  			foreach(lc, *context->params_list)
  			{
  				pindex++;
  				if (equal(node, (Node *) lfirst(lc)))
  					break;
  			}
  			if (lc == NULL)
  			{
  				/* not in list, so add it */
  				pindex++;
  				*context->params_list = lappend(*context->params_list, node);
  			}
  
  			printRemoteParam(pindex, node->vartype, node->vartypmod, context);
  		}
  		else
  		{
  			printRemotePlaceholder(node->vartype, node->vartypmod, context);
  		}
  	}
  }
  
  /*
   * Deparse given constant value into context->buf.
   *
   * This function has to be kept in sync with ruleutils.c's get_const_expr.
   * As for that function, showtype can be -1 to never show "::typename" decoration,
   * or +1 to always show it, or 0 to show it only if the constant wouldn't be assumed
   * to be the right type by default.
   */
  static void
  deparseConst(Const *node, deparse_expr_cxt *context, int showtype)
  {
  	StringInfo	buf = context->buf;
  	Oid			typoutput;
  	bool		typIsVarlena;
  	char	   *extval;
  	bool		isfloat = false;
  	bool		needlabel;
  
  	if (node->constisnull)
  	{
  		appendStringInfoString(buf, "NULL");
  		if (showtype >= 0)
  			appendStringInfo(buf, "::%s",
  							 deparse_type_name(node->consttype,
  											   node->consttypmod));
  		return;
  	}
  
  	getTypeOutputInfo(node->consttype,
  					  &typoutput, &typIsVarlena);
  	extval = OidOutputFunctionCall(typoutput, node->constvalue);
  
  	switch (node->consttype)
  	{
  		case INT2OID:
  		case INT4OID:
  		case INT8OID:
  		case OIDOID:
  		case FLOAT4OID:
  		case FLOAT8OID:
  		case NUMERICOID:
  			{
  				/*
  				 * No need to quote unless it's a special value such as 'NaN'.
  				 * See comments in get_const_expr().
  				 */
  				if (strspn(extval, "0123456789+-eE.") == strlen(extval))
  				{
  					if (extval[0] == '+' || extval[0] == '-')
  						appendStringInfo(buf, "(%s)", extval);
  					else
  						appendStringInfoString(buf, extval);
  					if (strcspn(extval, "eE.") != strlen(extval))
  						isfloat = true; /* it looks like a float */
  				}
  				else
  					appendStringInfo(buf, "'%s'", extval);
  			}
  			break;
  		case BITOID:
  		case VARBITOID:
  			appendStringInfo(buf, "B'%s'", extval);
  			break;
  		case BOOLOID:
  			if (strcmp(extval, "t") == 0)
  				appendStringInfoString(buf, "true");
  			else
  				appendStringInfoString(buf, "false");
  			break;
  		default:
  			deparseStringLiteral(buf, extval);
  			break;
  	}
  
  	pfree(extval);
  
  	if (showtype < 0)
  		return;
  
  	/*
  	 * For showtype == 0, append ::typename unless the constant will be
  	 * implicitly typed as the right type when it is read in.
  	 *
  	 * XXX this code has to be kept in sync with the behavior of the parser,
  	 * especially make_const.
  	 */
  	switch (node->consttype)
  	{
  		case BOOLOID:
  		case INT4OID:
  		case UNKNOWNOID:
  			needlabel = false;
  			break;
  		case NUMERICOID:
  			needlabel = !isfloat || (node->consttypmod >= 0);
  			break;
  		default:
  			needlabel = true;
  			break;
  	}
  	if (needlabel || showtype > 0)
  		appendStringInfo(buf, "::%s",
  						 deparse_type_name(node->consttype,
  										   node->consttypmod));
  }
  
  /*
   * Deparse given Param node.
   *
   * If we're generating the query "for real", add the Param to
   * context->params_list if it's not already present, and then use its index
   * in that list as the remote parameter number.  During EXPLAIN, there's
   * no need to identify a parameter number.
   */
  static void
  deparseParam(Param *node, deparse_expr_cxt *context)
  {
  	if (context->params_list)
  	{
  		int			pindex = 0;
  		ListCell   *lc;
  
  		/* find its index in params_list */
  		foreach(lc, *context->params_list)
  		{
  			pindex++;
  			if (equal(node, (Node *) lfirst(lc)))
  				break;
  		}
  		if (lc == NULL)
  		{
  			/* not in list, so add it */
  			pindex++;
  			*context->params_list = lappend(*context->params_list, node);
  		}
  
  		printRemoteParam(pindex, node->paramtype, node->paramtypmod, context);
  	}
  	else
  	{
  		printRemotePlaceholder(node->paramtype, node->paramtypmod, context);
  	}
  }
  
  /*
   * Deparse an array subscript expression.
   */
  static void
  deparseArrayRef(ArrayRef *node, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	ListCell   *lowlist_item;
  	ListCell   *uplist_item;
  
  	/* Always parenthesize the expression. */
  	appendStringInfoChar(buf, '(');
  
  	/*
  	 * Deparse referenced array expression first.  If that expression includes
  	 * a cast, we have to parenthesize to prevent the array subscript from
  	 * being taken as typename decoration.  We can avoid that in the typical
  	 * case of subscripting a Var, but otherwise do it.
  	 */
  	if (IsA(node->refexpr, Var))
  		deparseExpr(node->refexpr, context);
  	else
  	{
  		appendStringInfoChar(buf, '(');
  		deparseExpr(node->refexpr, context);
  		appendStringInfoChar(buf, ')');
  	}
  
  	/* Deparse subscript expressions. */
  	lowlist_item = list_head(node->reflowerindexpr);	/* could be NULL */
  	foreach(uplist_item, node->refupperindexpr)
  	{
  		appendStringInfoChar(buf, '[');
  		if (lowlist_item)
  		{
  			deparseExpr(lfirst(lowlist_item), context);
  			appendStringInfoChar(buf, ':');
  			lowlist_item = lnext(lowlist_item);
  		}
  		deparseExpr(lfirst(uplist_item), context);
  		appendStringInfoChar(buf, ']');
  	}
  
  	appendStringInfoChar(buf, ')');
  }
  
  /*
   * Deparse a function call.
   */
  static void
  deparseFuncExpr(FuncExpr *node, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	bool		use_variadic;
  	bool		first;
  	ListCell   *arg;
  
  	/*
  	 * If the function call came from an implicit coercion, then just show the
  	 * first argument.
  	 */
  	if (node->funcformat == COERCE_IMPLICIT_CAST)
  	{
  		deparseExpr((Expr *) linitial(node->args), context);
  		return;
  	}
  
  	/*
  	 * If the function call came from a cast, then show the first argument
  	 * plus an explicit cast operation.
  	 */
  	if (node->funcformat == COERCE_EXPLICIT_CAST)
  	{
  		Oid			rettype = node->funcresulttype;
  		int32		coercedTypmod;
  
  		/* Get the typmod if this is a length-coercion function */
  		(void) exprIsLengthCoercion((Node *) node, &coercedTypmod);
  
  		deparseExpr((Expr *) linitial(node->args), context);
  		appendStringInfo(buf, "::%s",
  						 deparse_type_name(rettype, coercedTypmod));
  		return;
  	}
  
  	/* Check if need to print VARIADIC (cf. ruleutils.c) */
  	use_variadic = node->funcvariadic;
  
  	/*
  	 * Normal function: display as proname(args).
  	 */
  	appendFunctionName(node->funcid, context);
  	appendStringInfoChar(buf, '(');
  
  	/* ... and all the arguments */
  	first = true;
  	foreach(arg, node->args)
  	{
  		if (!first)
  			appendStringInfoString(buf, ", ");
  		if (use_variadic && lnext(arg) == NULL)
  			appendStringInfoString(buf, "VARIADIC ");
  		deparseExpr((Expr *) lfirst(arg), context);
  		first = false;
  	}
  	appendStringInfoChar(buf, ')');
  }
  
  /*
   * Deparse given operator expression.   To avoid problems around
   * priority of operations, we always parenthesize the arguments.
   */
  static void
  deparseOpExpr(OpExpr *node, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	HeapTuple	tuple;
  	Form_pg_operator form;
  	char		oprkind;
  	ListCell   *arg;
  
  	/* Retrieve information about the operator from system catalog. */
  	tuple = SearchSysCache1(OPEROID, ObjectIdGetDatum(node->opno));
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for operator %u", node->opno);
  	form = (Form_pg_operator) GETSTRUCT(tuple);
  	oprkind = form->oprkind;
  
  	/* Sanity check. */
  	Assert((oprkind == 'r' && list_length(node->args) == 1) ||
  		   (oprkind == 'l' && list_length(node->args) == 1) ||
  		   (oprkind == 'b' && list_length(node->args) == 2));
  
  	/* Always parenthesize the expression. */
  	appendStringInfoChar(buf, '(');
  
  	/* Deparse left operand. */
  	if (oprkind == 'r' || oprkind == 'b')
  	{
  		arg = list_head(node->args);
  		deparseExpr(lfirst(arg), context);
  		appendStringInfoChar(buf, ' ');
  	}
  
  	/* Deparse operator name. */
  	deparseOperatorName(buf, form);
  
  	/* Deparse right operand. */
  	if (oprkind == 'l' || oprkind == 'b')
  	{
  		arg = list_tail(node->args);
  		appendStringInfoChar(buf, ' ');
  		deparseExpr(lfirst(arg), context);
  	}
  
  	appendStringInfoChar(buf, ')');
  
  	ReleaseSysCache(tuple);
  }
  
  /*
   * Print the name of an operator.
   */
  static void
  deparseOperatorName(StringInfo buf, Form_pg_operator opform)
  {
  	char	   *opname;
  
  	/* opname is not a SQL identifier, so we should not quote it. */
  	opname = NameStr(opform->oprname);
  
  	/* Print schema name only if it's not pg_catalog */
  	if (opform->oprnamespace != PG_CATALOG_NAMESPACE)
  	{
  		const char *opnspname;
  
  		opnspname = get_namespace_name(opform->oprnamespace);
  		/* Print fully qualified operator name. */
  		appendStringInfo(buf, "OPERATOR(%s.%s)",
  						 quote_identifier(opnspname), opname);
  	}
  	else
  	{
  		/* Just print operator name. */
  		appendStringInfoString(buf, opname);
  	}
  }
  
  /*
   * Deparse IS DISTINCT FROM.
   */
  static void
  deparseDistinctExpr(DistinctExpr *node, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  
  	Assert(list_length(node->args) == 2);
  
  	appendStringInfoChar(buf, '(');
  	deparseExpr(linitial(node->args), context);
  	appendStringInfoString(buf, " IS DISTINCT FROM ");
  	deparseExpr(lsecond(node->args), context);
  	appendStringInfoChar(buf, ')');
  }
  
  /*
   * Deparse given ScalarArrayOpExpr expression.  To avoid problems
   * around priority of operations, we always parenthesize the arguments.
   */
  static void
  deparseScalarArrayOpExpr(ScalarArrayOpExpr *node, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	HeapTuple	tuple;
  	Form_pg_operator form;
  	Expr	   *arg1;
  	Expr	   *arg2;
  
  	/* Retrieve information about the operator from system catalog. */
  	tuple = SearchSysCache1(OPEROID, ObjectIdGetDatum(node->opno));
  	if (!HeapTupleIsValid(tuple))
  		elog(ERROR, "cache lookup failed for operator %u", node->opno);
  	form = (Form_pg_operator) GETSTRUCT(tuple);
  
  	/* Sanity check. */
  	Assert(list_length(node->args) == 2);
  
  	/* Always parenthesize the expression. */
  	appendStringInfoChar(buf, '(');
  
  	/* Deparse left operand. */
  	arg1 = linitial(node->args);
  	deparseExpr(arg1, context);
  	appendStringInfoChar(buf, ' ');
  
  	/* Deparse operator name plus decoration. */
  	deparseOperatorName(buf, form);
  	appendStringInfo(buf, " %s (", node->useOr ? "ANY" : "ALL");
  
  	/* Deparse right operand. */
  	arg2 = lsecond(node->args);
  	deparseExpr(arg2, context);
  
  	appendStringInfoChar(buf, ')');
  
  	/* Always parenthesize the expression. */
  	appendStringInfoChar(buf, ')');
  
  	ReleaseSysCache(tuple);
  }
  
  /*
   * Deparse a RelabelType (binary-compatible cast) node.
   */
  static void
  deparseRelabelType(RelabelType *node, deparse_expr_cxt *context)
  {
  	deparseExpr(node->arg, context);
  	if (node->relabelformat != COERCE_IMPLICIT_CAST)
  		appendStringInfo(context->buf, "::%s",
  						 deparse_type_name(node->resulttype,
  										   node->resulttypmod));
  }
  
  /*
   * Deparse a BoolExpr node.
   */
  static void
  deparseBoolExpr(BoolExpr *node, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	const char *op = NULL;		/* keep compiler quiet */
  	bool		first;
  	ListCell   *lc;
  
  	switch (node->boolop)
  	{
  		case AND_EXPR:
  			op = "AND";
  			break;
  		case OR_EXPR:
  			op = "OR";
  			break;
  		case NOT_EXPR:
  			appendStringInfoString(buf, "(NOT ");
  			deparseExpr(linitial(node->args), context);
  			appendStringInfoChar(buf, ')');
  			return;
  	}
  
  	appendStringInfoChar(buf, '(');
  	first = true;
  	foreach(lc, node->args)
  	{
  		if (!first)
  			appendStringInfo(buf, " %s ", op);
  		deparseExpr((Expr *) lfirst(lc), context);
  		first = false;
  	}
  	appendStringInfoChar(buf, ')');
  }
  
  /*
   * Deparse IS [NOT] NULL expression.
   */
  static void
  deparseNullTest(NullTest *node, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  
  	appendStringInfoChar(buf, '(');
  	deparseExpr(node->arg, context);
  
  	/*
  	 * For scalar inputs, we prefer to print as IS [NOT] NULL, which is
  	 * shorter and traditional.  If it's a rowtype input but we're applying a
  	 * scalar test, must print IS [NOT] DISTINCT FROM NULL to be semantically
  	 * correct.
  	 */
  	if (node->argisrow || !type_is_rowtype(exprType((Node *) node->arg)))
  	{
  		if (node->nulltesttype == IS_NULL)
  			appendStringInfoString(buf, " IS NULL)");
  		else
  			appendStringInfoString(buf, " IS NOT NULL)");
  	}
  	else
  	{
  		if (node->nulltesttype == IS_NULL)
  			appendStringInfoString(buf, " IS NOT DISTINCT FROM NULL)");
  		else
  			appendStringInfoString(buf, " IS DISTINCT FROM NULL)");
  	}
  }
  
  /*
   * Deparse ARRAY[...] construct.
   */
  static void
  deparseArrayExpr(ArrayExpr *node, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	bool		first = true;
  	ListCell   *lc;
  
  	appendStringInfoString(buf, "ARRAY[");
  	foreach(lc, node->elements)
  	{
  		if (!first)
  			appendStringInfoString(buf, ", ");
  		deparseExpr(lfirst(lc), context);
  		first = false;
  	}
  	appendStringInfoChar(buf, ']');
  
  	/* If the array is empty, we need an explicit cast to the array type. */
  	if (node->elements == NIL)
  		appendStringInfo(buf, "::%s",
  						 deparse_type_name(node->array_typeid, -1));
  }
  
  /*
   * Deparse an Aggref node.
   */
  static void
  deparseAggref(Aggref *node, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	bool		use_variadic;
  
  	/* Only basic, non-split aggregation accepted. */
  	Assert(node->aggsplit == AGGSPLIT_SIMPLE);
  
  	/* Check if need to print VARIADIC (cf. ruleutils.c) */
  	use_variadic = node->aggvariadic;
  
  	/* Find aggregate name from aggfnoid which is a pg_proc entry */
  	appendFunctionName(node->aggfnoid, context);
  	appendStringInfoChar(buf, '(');
  
  	/* Add DISTINCT */
  	appendStringInfo(buf, "%s", (node->aggdistinct != NIL) ? "DISTINCT " : "");
  
  	if (AGGKIND_IS_ORDERED_SET(node->aggkind))
  	{
  		/* Add WITHIN GROUP (ORDER BY ..) */
  		ListCell   *arg;
  		bool		first = true;
  
  		Assert(!node->aggvariadic);
  		Assert(node->aggorder != NIL);
  
  		foreach(arg, node->aggdirectargs)
  		{
  			if (!first)
  				appendStringInfoString(buf, ", ");
  			first = false;
  
  			deparseExpr((Expr *) lfirst(arg), context);
  		}
  
  		appendStringInfoString(buf, ") WITHIN GROUP (ORDER BY ");
  		appendAggOrderBy(node->aggorder, node->args, context);
  	}
  	else
  	{
  		/* aggstar can be set only in zero-argument aggregates */
  		if (node->aggstar)
  			appendStringInfoChar(buf, '*');
  		else
  		{
  			ListCell   *arg;
  			bool		first = true;
  
  			/* Add all the arguments */
  			foreach(arg, node->args)
  			{
  				TargetEntry *tle = (TargetEntry *) lfirst(arg);
  				Node	   *n = (Node *) tle->expr;
  
  				if (tle->resjunk)
  					continue;
  
  				if (!first)
  					appendStringInfoString(buf, ", ");
  				first = false;
  
  				/* Add VARIADIC */
  				if (use_variadic && lnext(arg) == NULL)
  					appendStringInfoString(buf, "VARIADIC ");
  
  				deparseExpr((Expr *) n, context);
  			}
  		}
  
  		/* Add ORDER BY */
  		if (node->aggorder != NIL)
  		{
  			appendStringInfoString(buf, " ORDER BY ");
  			appendAggOrderBy(node->aggorder, node->args, context);
  		}
  	}
  
  	/* Add FILTER (WHERE ..) */
  	if (node->aggfilter != NULL)
  	{
  		appendStringInfoString(buf, ") FILTER (WHERE ");
  		deparseExpr((Expr *) node->aggfilter, context);
  	}
  
  	appendStringInfoChar(buf, ')');
  }
  
  /*
   * Append ORDER BY within aggregate function.
   */
  static void
  appendAggOrderBy(List *orderList, List *targetList, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	ListCell   *lc;
  	bool		first = true;
  
  	foreach(lc, orderList)
  	{
  		SortGroupClause *srt = (SortGroupClause *) lfirst(lc);
  		Node	   *sortexpr;
  		Oid			sortcoltype;
  		TypeCacheEntry *typentry;
  
  		if (!first)
  			appendStringInfoString(buf, ", ");
  		first = false;
  
  		sortexpr = deparseSortGroupClause(srt->tleSortGroupRef, targetList,
  										  context);
  		sortcoltype = exprType(sortexpr);
  		/* See whether operator is default < or > for datatype */
  		typentry = lookup_type_cache(sortcoltype,
  									 TYPECACHE_LT_OPR | TYPECACHE_GT_OPR);
  		if (srt->sortop == typentry->lt_opr)
  			appendStringInfoString(buf, " ASC");
  		else if (srt->sortop == typentry->gt_opr)
  			appendStringInfoString(buf, " DESC");
  		else
  		{
  			HeapTuple	opertup;
  			Form_pg_operator operform;
  
  			appendStringInfoString(buf, " USING ");
  
  			/* Append operator name. */
  			opertup = SearchSysCache1(OPEROID, ObjectIdGetDatum(srt->sortop));
  			if (!HeapTupleIsValid(opertup))
  				elog(ERROR, "cache lookup failed for operator %u", srt->sortop);
  			operform = (Form_pg_operator) GETSTRUCT(opertup);
  			deparseOperatorName(buf, operform);
  			ReleaseSysCache(opertup);
  		}
  
  		if (srt->nulls_first)
  			appendStringInfoString(buf, " NULLS FIRST");
  		else
  			appendStringInfoString(buf, " NULLS LAST");
  	}
  }
  
  /*
   * Print the representation of a parameter to be sent to the remote side.
   *
   * Note: we always label the Param's type explicitly rather than relying on
   * transmitting a numeric type OID in PQexecParams().  This allows us to
   * avoid assuming that types have the same OIDs on the remote side as they
   * do locally --- they need only have the same names.
   */
  static void
  printRemoteParam(int paramindex, Oid paramtype, int32 paramtypmod,
  				 deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	char	   *ptypename = deparse_type_name(paramtype, paramtypmod);
  
  	appendStringInfo(buf, "$%d::%s", paramindex, ptypename);
  }
  
  /*
   * Print the representation of a placeholder for a parameter that will be
   * sent to the remote side at execution time.
   *
   * This is used when we're just trying to EXPLAIN the remote query.
   * We don't have the actual value of the runtime parameter yet, and we don't
   * want the remote planner to generate a plan that depends on such a value
   * anyway.  Thus, we can't do something simple like "$1::paramtype".
   * Instead, we emit "((SELECT null::paramtype)::paramtype)".
   * In all extant versions of Postgres, the planner will see that as an unknown
   * constant value, which is what we want.  This might need adjustment if we
   * ever make the planner flatten scalar subqueries.  Note: the reason for the
   * apparently useless outer cast is to ensure that the representation as a
   * whole will be parsed as an a_expr and not a select_with_parens; the latter
   * would do the wrong thing in the context "x = ANY(...)".
   */
  static void
  printRemotePlaceholder(Oid paramtype, int32 paramtypmod,
  					   deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	char	   *ptypename = deparse_type_name(paramtype, paramtypmod);
  
  	appendStringInfo(buf, "((SELECT null::%s)::%s)", ptypename, ptypename);
  }
  
  /*
   * Deparse GROUP BY clause.
   */
  static void
  appendGroupByClause(List *tlist, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	Query	   *query = context->root->parse;
  	ListCell   *lc;
  	bool		first = true;
  
  	/* Nothing to be done, if there's no GROUP BY clause in the query. */
  	if (!query->groupClause)
  		return;
  
  	appendStringInfo(buf, " GROUP BY ");
  
  	/*
  	 * Queries with grouping sets are not pushed down, so we don't expect
  	 * grouping sets here.
  	 */
  	Assert(!query->groupingSets);
  
  	foreach(lc, query->groupClause)
  	{
  		SortGroupClause *grp = (SortGroupClause *) lfirst(lc);
  
  		if (!first)
  			appendStringInfoString(buf, ", ");
  		first = false;
  
  		deparseSortGroupClause(grp->tleSortGroupRef, tlist, context);
  	}
  }
  
  /*
   * Deparse ORDER BY clause according to the given pathkeys for given base
   * relation. From given pathkeys expressions belonging entirely to the given
   * base relation are obtained and deparsed.
   */
  static void
  appendOrderByClause(List *pathkeys, deparse_expr_cxt *context)
  {
  	ListCell   *lcell;
  	int			nestlevel;
  	char	   *delim = " ";
  	RelOptInfo *baserel = context->scanrel;
  	StringInfo	buf = context->buf;
  
  	/* Make sure any constants in the exprs are printed portably */
  	nestlevel = set_transmission_modes();
  
  	appendStringInfo(buf, " ORDER BY");
  	foreach(lcell, pathkeys)
  	{
  		PathKey    *pathkey = lfirst(lcell);
  		Expr	   *em_expr;
  
  		em_expr = find_em_expr_for_rel(pathkey->pk_eclass, baserel);
  		Assert(em_expr != NULL);
  
  		appendStringInfoString(buf, delim);
  		deparseExpr(em_expr, context);
  		if (pathkey->pk_strategy == BTLessStrategyNumber)
  			appendStringInfoString(buf, " ASC");
  		else
  			appendStringInfoString(buf, " DESC");
  
  		if (pathkey->pk_nulls_first)
  			appendStringInfoString(buf, " NULLS FIRST");
  		else
  			appendStringInfoString(buf, " NULLS LAST");
  
  		delim = ", ";
  	}
  	reset_transmission_modes(nestlevel);
  }
  
  /*
   * appendFunctionName
   *		Deparses function name from given function oid.
   */
  static void
  appendFunctionName(Oid funcid, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	HeapTuple	proctup;
  	Form_pg_proc procform;
  	const char *proname;
  
  	proctup = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
  	if (!HeapTupleIsValid(proctup))
  		elog(ERROR, "cache lookup failed for function %u", funcid);
  	procform = (Form_pg_proc) GETSTRUCT(proctup);
  
  	/* Print schema name only if it's not pg_catalog */
  	if (procform->pronamespace != PG_CATALOG_NAMESPACE)
  	{
  		const char *schemaname;
  
  		schemaname = get_namespace_name(procform->pronamespace);
  		appendStringInfo(buf, "%s.", quote_identifier(schemaname));
  	}
  
  	/* Always print the function name */
  	proname = NameStr(procform->proname);
  	appendStringInfo(buf, "%s", quote_identifier(proname));
  
  	ReleaseSysCache(proctup);
  }
  
  /*
   * Appends a sort or group clause.
   *
   * Like get_rule_sortgroupclause(), returns the expression tree, so caller
   * need not find it again.
   */
  static Node *
  deparseSortGroupClause(Index ref, List *tlist, deparse_expr_cxt *context)
  {
  	StringInfo	buf = context->buf;
  	TargetEntry *tle;
  	Expr	   *expr;
  
  	tle = get_sortgroupref_tle(ref, tlist);
  	expr = tle->expr;
  
  	if (expr && IsA(expr, Const))
  	{
  		/*
  		 * Force a typecast here so that we don't emit something like "GROUP
  		 * BY 2", which will be misconstrued as a column position rather than
  		 * a constant.
  		 */
  		deparseConst((Const *) expr, context, 1);
  	}
  	else if (!expr || IsA(expr, Var))
  		deparseExpr(expr, context);
  	else
  	{
  		/* Always parenthesize the expression. */
  		appendStringInfoString(buf, "(");
  		deparseExpr(expr, context);
  		appendStringInfoString(buf, ")");
  	}
  
  	return (Node *) expr;
  }
  