text: /*-------------------------------------------------------------------------
   *
   * functions.c
   *	  Execution of SQL-language functions
   *
   * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  src/backend/executor/functions.c
   *
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include "access/htup_details.h"
  #include "access/xact.h"
  #include "catalog/pg_proc.h"
  #include "catalog/pg_type.h"
  #include "executor/functions.h"
  #include "funcapi.h"
  #include "miscadmin.h"
  #include "nodes/makefuncs.h"
  #include "nodes/nodeFuncs.h"
  #include "parser/parse_coerce.h"
  #include "parser/parse_func.h"
  #include "storage/proc.h"
  #include "tcop/utility.h"
  #include "utils/builtins.h"
  #include "utils/datum.h"
  #include "utils/lsyscache.h"
  #include "utils/memutils.h"
  #include "utils/snapmgr.h"
  #include "utils/syscache.h"
  
  
  /*
   * Specialized DestReceiver for collecting query output in a SQL function
   */
  typedef struct
  {
  	DestReceiver pub;			/* publicly-known function pointers */
  	Tuplestorestate *tstore;	/* where to put result tuples */
  	MemoryContext cxt;			/* context containing tstore */
  	JunkFilter *filter;			/* filter to convert tuple type */
  } DR_sqlfunction;
  
  /*
   * We have an execution_state record for each query in a function.  Each
   * record contains a plantree for its query.  If the query is currently in
   * F_EXEC_RUN state then there's a QueryDesc too.
   *
   * The "next" fields chain together all the execution_state records generated
   * from a single original parsetree.  (There will only be more than one in
   * case of rule expansion of the original parsetree.)
   */
  typedef enum
  {
  	F_EXEC_START, F_EXEC_RUN, F_EXEC_DONE
  } ExecStatus;
  
  typedef struct execution_state
  {
  	struct execution_state *next;
  	ExecStatus	status;
  	bool		setsResult;		/* true if this query produces func's result */
  	bool		lazyEval;		/* true if should fetch one row at a time */
  	PlannedStmt *stmt;			/* plan for this query */
  	QueryDesc  *qd;				/* null unless status == RUN */
  } execution_state;
  
  
  /*
   * An SQLFunctionCache record is built during the first call,
   * and linked to from the fn_extra field of the FmgrInfo struct.
   *
   * Note that currently this has only the lifespan of the calling query.
   * Someday we should rewrite this code to use plancache.c to save parse/plan
   * results for longer than that.
   *
   * Physically, though, the data has the lifespan of the FmgrInfo that's used
   * to call the function, and there are cases (particularly with indexes)
   * where the FmgrInfo might survive across transactions.  We cannot assume
   * that the parse/plan trees are good for longer than the (sub)transaction in
   * which parsing was done, so we must mark the record with the LXID/subxid of
   * its creation time, and regenerate everything if that's obsolete.  To avoid
   * memory leakage when we do have to regenerate things, all the data is kept
   * in a sub-context of the FmgrInfo's fn_mcxt.
   */
  typedef struct
  {
  	char	   *fname;			/* function name (for error msgs) */
  	char	   *src;			/* function body text (for error msgs) */
  
  	SQLFunctionParseInfoPtr pinfo;	/* data for parser callback hooks */
  
  	Oid			rettype;		/* actual return type */
  	int16		typlen;			/* length of the return type */
  	bool		typbyval;		/* true if return type is pass by value */
  	bool		returnsSet;		/* true if returning multiple rows */
  	bool		returnsTuple;	/* true if returning whole tuple result */
  	bool		shutdown_reg;	/* true if registered shutdown callback */
  	bool		readonly_func;	/* true to run in "read only" mode */
  	bool		lazyEval;		/* true if using lazyEval for result query */
  
  	ParamListInfo paramLI;		/* Param list representing current args */
  
  	Tuplestorestate *tstore;	/* where we accumulate result tuples */
  
  	JunkFilter *junkFilter;		/* will be NULL if function returns VOID */
  
  	/*
  	 * func_state is a List of execution_state records, each of which is the
  	 * first for its original parsetree, with any additional records chained
  	 * to it via the "next" fields.  This sublist structure is needed to keep
  	 * track of where the original query boundaries are.
  	 */
  	List	   *func_state;
  
  	MemoryContext fcontext;		/* memory context holding this struct and all
  								 * subsidiary data */
  
  	LocalTransactionId lxid;	/* lxid in which cache was made */
  	SubTransactionId subxid;	/* subxid in which cache was made */
  } SQLFunctionCache;
  
  typedef SQLFunctionCache *SQLFunctionCachePtr;
  
  /*
   * Data structure needed by the parser callback hooks to resolve parameter
   * references during parsing of a SQL function's body.  This is separate from
   * SQLFunctionCache since we sometimes do parsing separately from execution.
   */
  typedef struct SQLFunctionParseInfo
  {
  	char	   *fname;			/* function's name */
  	int			nargs;			/* number of input arguments */
  	Oid		   *argtypes;		/* resolved types of input arguments */
  	char	  **argnames;		/* names of input arguments; NULL if none */
  	/* Note that argnames[i] can be NULL, if some args are unnamed */
  	Oid			collation;		/* function's input collation, if known */
  }			SQLFunctionParseInfo;
  
  
  /* non-export function prototypes */
  static Node *sql_fn_param_ref(ParseState *pstate, ParamRef *pref);
  static Node *sql_fn_post_column_ref(ParseState *pstate,
  					   ColumnRef *cref, Node *var);
  static Node *sql_fn_make_param(SQLFunctionParseInfoPtr pinfo,
  				  int paramno, int location);
  static Node *sql_fn_resolve_param_name(SQLFunctionParseInfoPtr pinfo,
  						  const char *paramname, int location);
  static List *init_execution_state(List *queryTree_list,
  					 SQLFunctionCachePtr fcache,
  					 bool lazyEvalOK);
  static void init_sql_fcache(FmgrInfo *finfo, Oid collation, bool lazyEvalOK);
  static void postquel_start(execution_state *es, SQLFunctionCachePtr fcache);
  static bool postquel_getnext(execution_state *es, SQLFunctionCachePtr fcache);
  static void postquel_end(execution_state *es);
  static void postquel_sub_params(SQLFunctionCachePtr fcache,
  					FunctionCallInfo fcinfo);
  static Datum postquel_get_single_result(TupleTableSlot *slot,
  						   FunctionCallInfo fcinfo,
  						   SQLFunctionCachePtr fcache,
  						   MemoryContext resultcontext);
  static void sql_exec_error_callback(void *arg);
  static void ShutdownSQLFunction(Datum arg);
  static void sqlfunction_startup(DestReceiver *self, int operation, TupleDesc typeinfo);
  static bool sqlfunction_receive(TupleTableSlot *slot, DestReceiver *self);
  static void sqlfunction_shutdown(DestReceiver *self);
  static void sqlfunction_destroy(DestReceiver *self);
  
  
  /*
   * Prepare the SQLFunctionParseInfo struct for parsing a SQL function body
   *
   * This includes resolving actual types of polymorphic arguments.
   *
   * call_expr can be passed as NULL, but then we will fail if there are any
   * polymorphic arguments.
   */
  SQLFunctionParseInfoPtr
  prepare_sql_fn_parse_info(HeapTuple procedureTuple,
  						  Node *call_expr,
  						  Oid inputCollation)
  {
  	SQLFunctionParseInfoPtr pinfo;
  	Form_pg_proc procedureStruct = (Form_pg_proc) GETSTRUCT(procedureTuple);
  	int			nargs;
  
  	pinfo = (SQLFunctionParseInfoPtr) palloc0(sizeof(SQLFunctionParseInfo));
  
  	/* Function's name (only) can be used to qualify argument names */
  	pinfo->fname = pstrdup(NameStr(procedureStruct->proname));
  
  	/* Save the function's input collation */
  	pinfo->collation = inputCollation;
  
  	/*
  	 * Copy input argument types from the pg_proc entry, then resolve any
  	 * polymorphic types.
  	 */
  	pinfo->nargs = nargs = procedureStruct->pronargs;
  	if (nargs > 0)
  	{
  		Oid		   *argOidVect;
  		int			argnum;
  
  		argOidVect = (Oid *) palloc(nargs * sizeof(Oid));
  		memcpy(argOidVect,
  			   procedureStruct->proargtypes.values,
  			   nargs * sizeof(Oid));
  
  		for (argnum = 0; argnum < nargs; argnum++)
  		{
  			Oid			argtype = argOidVect[argnum];
  
  			if (IsPolymorphicType(argtype))
  			{
  				argtype = get_call_expr_argtype(call_expr, argnum);
  				if (argtype == InvalidOid)
  					ereport(ERROR,
  							(errcode(ERRCODE_DATATYPE_MISMATCH),
  							 errmsg("could not determine actual type of argument declared %s",
  									format_type_be(argOidVect[argnum]))));
  				argOidVect[argnum] = argtype;
  			}
  		}
  
  		pinfo->argtypes = argOidVect;
  	}
  
  	/*
  	 * Collect names of arguments, too, if any
  	 */
  	if (nargs > 0)
  	{
  		Datum		proargnames;
  		Datum		proargmodes;
  		int			n_arg_names;
  		bool		isNull;
  
  		proargnames = SysCacheGetAttr(PROCNAMEARGSNSP, procedureTuple,
  									  Anum_pg_proc_proargnames,
  									  &isNull);
  		if (isNull)
  			proargnames = PointerGetDatum(NULL);	/* just to be sure */
  
  		proargmodes = SysCacheGetAttr(PROCNAMEARGSNSP, procedureTuple,
  									  Anum_pg_proc_proargmodes,
  									  &isNull);
  		if (isNull)
  			proargmodes = PointerGetDatum(NULL);	/* just to be sure */
  
  		n_arg_names = get_func_input_arg_names(proargnames, proargmodes,
  											   &pinfo->argnames);
  
  		/* Paranoia: ignore the result if too few array entries */
  		if (n_arg_names < nargs)
  			pinfo->argnames = NULL;
  	}
  	else
  		pinfo->argnames = NULL;
  
  	return pinfo;
  }
  
  /*
   * Parser setup hook for parsing a SQL function body.
   */
  void
  sql_fn_parser_setup(struct ParseState *pstate, SQLFunctionParseInfoPtr pinfo)
  {
  	pstate->p_pre_columnref_hook = NULL;
  	pstate->p_post_columnref_hook = sql_fn_post_column_ref;
  	pstate->p_paramref_hook = sql_fn_param_ref;
  	/* no need to use p_coerce_param_hook */
  	pstate->p_ref_hook_state = (void *) pinfo;
  }
  
  /*
   * sql_fn_post_column_ref		parser callback for ColumnRefs
   */
  static Node *
  sql_fn_post_column_ref(ParseState *pstate, ColumnRef *cref, Node *var)
  {
  	SQLFunctionParseInfoPtr pinfo = (SQLFunctionParseInfoPtr) pstate->p_ref_hook_state;
  	int			nnames;
  	Node	   *field1;
  	Node	   *subfield = NULL;
  	const char *name1;
  	const char *name2 = NULL;
  	Node	   *param;
  
  	/*
  	 * Never override a table-column reference.  This corresponds to
  	 * considering the parameter names to appear in a scope outside the
  	 * individual SQL commands, which is what we want.
  	 */
  	if (var != NULL)
  		return NULL;
  
  	/*----------
  	 * The allowed syntaxes are:
  	 *
  	 * A		A = parameter name
  	 * A.B		A = function name, B = parameter name
  	 *			OR: A = record-typed parameter name, B = field name
  	 *			(the first possibility takes precedence)
  	 * A.B.C	A = function name, B = record-typed parameter name,
  	 *			C = field name
  	 * A.*		Whole-row reference to composite parameter A.
  	 * A.B.*	Same, with A = function name, B = parameter name
  	 *
  	 * Here, it's sufficient to ignore the "*" in the last two cases --- the
  	 * main parser will take care of expanding the whole-row reference.
  	 *----------
  	 */
  	nnames = list_length(cref->fields);
  
  	if (nnames > 3)
  		return NULL;
  
  	if (IsA(llast(cref->fields), A_Star))
  		nnames--;
  
  	field1 = (Node *) linitial(cref->fields);
  	Assert(IsA(field1, String));
  	name1 = strVal(field1);
  	if (nnames > 1)
  	{
  		subfield = (Node *) lsecond(cref->fields);
  		Assert(IsA(subfield, String));
  		name2 = strVal(subfield);
  	}
  
  	if (nnames == 3)
  	{
  		/*
  		 * Three-part name: if the first part doesn't match the function name,
  		 * we can fail immediately. Otherwise, look up the second part, and
  		 * take the third part to be a field reference.
  		 */
  		if (strcmp(name1, pinfo->fname) != 0)
  			return NULL;
  
  		param = sql_fn_resolve_param_name(pinfo, name2, cref->location);
  
  		subfield = (Node *) lthird(cref->fields);
  		Assert(IsA(subfield, String));
  	}
  	else if (nnames == 2 && strcmp(name1, pinfo->fname) == 0)
  	{
  		/*
  		 * Two-part name with first part matching function name: first see if
  		 * second part matches any parameter name.
  		 */
  		param = sql_fn_resolve_param_name(pinfo, name2, cref->location);
  
  		if (param)
  		{
  			/* Yes, so this is a parameter reference, no subfield */
  			subfield = NULL;
  		}
  		else
  		{
  			/* No, so try to match as parameter name and subfield */
  			param = sql_fn_resolve_param_name(pinfo, name1, cref->location);
  		}
  	}
  	else
  	{
  		/* Single name, or parameter name followed by subfield */
  		param = sql_fn_resolve_param_name(pinfo, name1, cref->location);
  	}
  
  	if (!param)
  		return NULL;			/* No match */
  
  	if (subfield)
  	{
  		/*
  		 * Must be a reference to a field of a composite parameter; otherwise
  		 * ParseFuncOrColumn will return NULL, and we'll fail back at the
  		 * caller.
  		 */
  		param = ParseFuncOrColumn(pstate,
  								  list_make1(subfield),
  								  list_make1(param),
  								  pstate->p_last_srf,
  								  NULL,
  								  cref->location);
  	}
  
  	return param;
  }
  
  /*
   * sql_fn_param_ref		parser callback for ParamRefs ($n symbols)
   */
  static Node *
  sql_fn_param_ref(ParseState *pstate, ParamRef *pref)
  {
  	SQLFunctionParseInfoPtr pinfo = (SQLFunctionParseInfoPtr) pstate->p_ref_hook_state;
  	int			paramno = pref->number;
  
  	/* Check parameter number is valid */
  	if (paramno <= 0 || paramno > pinfo->nargs)
  		return NULL;			/* unknown parameter number */
  
  	return sql_fn_make_param(pinfo, paramno, pref->location);
  }
  
  /*
   * sql_fn_make_param		construct a Param node for the given paramno
   */
  static Node *
  sql_fn_make_param(SQLFunctionParseInfoPtr pinfo,
  				  int paramno, int location)
  {
  	Param	   *param;
  
  	param = makeNode(Param);
  	param->paramkind = PARAM_EXTERN;
  	param->paramid = paramno;
  	param->paramtype = pinfo->argtypes[paramno - 1];
  	param->paramtypmod = -1;
  	param->paramcollid = get_typcollation(param->paramtype);
  	param->location = location;
  
  	/*
  	 * If we have a function input collation, allow it to override the
  	 * type-derived collation for parameter symbols.  (XXX perhaps this should
  	 * not happen if the type collation is not default?)
  	 */
  	if (OidIsValid(pinfo->collation) && OidIsValid(param->paramcollid))
  		param->paramcollid = pinfo->collation;
  
  	return (Node *) param;
  }
  
  /*
   * Search for a function parameter of the given name; if there is one,
   * construct and return a Param node for it.  If not, return NULL.
   * Helper function for sql_fn_post_column_ref.
   */
  static Node *
  sql_fn_resolve_param_name(SQLFunctionParseInfoPtr pinfo,
  						  const char *paramname, int location)
  {
  	int			i;
  
  	if (pinfo->argnames == NULL)
  		return NULL;
  
  	for (i = 0; i < pinfo->nargs; i++)
  	{
  		if (pinfo->argnames[i] && strcmp(pinfo->argnames[i], paramname) == 0)
  			return sql_fn_make_param(pinfo, i + 1, location);
  	}
  
  	return NULL;
  }
  
  /*
   * Set up the per-query execution_state records for a SQL function.
   *
   * The input is a List of Lists of parsed and rewritten, but not planned,
   * querytrees.  The sublist structure denotes the original query boundaries.
   */
  static List *
  init_execution_state(List *queryTree_list,
  					 SQLFunctionCachePtr fcache,
  					 bool lazyEvalOK)
  {
  	List	   *eslist = NIL;
  	execution_state *lasttages = NULL;
  	ListCell   *lc1;
  
  	foreach(lc1, queryTree_list)
  	{
  		List	   *qtlist = lfirst_node(List, lc1);
  		execution_state *firstes = NULL;
  		execution_state *preves = NULL;
  		ListCell   *lc2;
  
  		foreach(lc2, qtlist)
  		{
  			Query	   *queryTree = lfirst_node(Query, lc2);
  			PlannedStmt *stmt;
  			execution_state *newes;
  
  			/* Plan the query if needed */
  			if (queryTree->commandType == CMD_UTILITY)
  			{
  				/* Utility commands require no planning. */
  				stmt = makeNode(PlannedStmt);
  				stmt->commandType = CMD_UTILITY;
  				stmt->canSetTag = queryTree->canSetTag;
  				stmt->utilityStmt = queryTree->utilityStmt;
  				stmt->stmt_location = queryTree->stmt_location;
  				stmt->stmt_len = queryTree->stmt_len;
  			}
  			else
  				stmt = pg_plan_query(queryTree,
  									 CURSOR_OPT_PARALLEL_OK,
  									 NULL);
  
  			/*
  			 * Precheck all commands for validity in a function.  This should
  			 * generally match the restrictions spi.c applies.
  			 */
  			if (stmt->commandType == CMD_UTILITY)
  			{
  				if (IsA(stmt->utilityStmt, CopyStmt) &&
  					((CopyStmt *) stmt->utilityStmt)->filename == NULL)
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  							 errmsg("cannot COPY to/from client in a SQL function")));
  
  				if (IsA(stmt->utilityStmt, TransactionStmt))
  					ereport(ERROR,
  							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					/* translator: %s is a SQL statement name */
  							 errmsg("%s is not allowed in a SQL function",
  									CreateCommandTag(stmt->utilityStmt))));
  			}
  
  			if (fcache->readonly_func && !CommandIsReadOnly(stmt))
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				/* translator: %s is a SQL statement name */
  						 errmsg("%s is not allowed in a non-volatile function",
  								CreateCommandTag((Node *) stmt))));
  
  			if (IsInParallelMode() && !CommandIsReadOnly(stmt))
  				PreventCommandIfParallelMode(CreateCommandTag((Node *) stmt));
  
  			/* OK, build the execution_state for this query */
  			newes = (execution_state *) palloc(sizeof(execution_state));
  			if (preves)
  				preves->next = newes;
  			else
  				firstes = newes;
  
  			newes->next = NULL;
  			newes->status = F_EXEC_START;
  			newes->setsResult = false;	/* might change below */
  			newes->lazyEval = false;	/* might change below */
  			newes->stmt = stmt;
  			newes->qd = NULL;
  
  			if (queryTree->canSetTag)
  				lasttages = newes;
  
  			preves = newes;
  		}
  
  		eslist = lappend(eslist, firstes);
  	}
  
  	/*
  	 * Mark the last canSetTag query as delivering the function result; then,
  	 * if it is a plain SELECT, mark it for lazy evaluation. If it's not a
  	 * SELECT we must always run it to completion.
  	 *
  	 * Note: at some point we might add additional criteria for whether to use
  	 * lazy eval.  However, we should prefer to use it whenever the function
  	 * doesn't return set, since fetching more than one row is useless in that
  	 * case.
  	 *
  	 * Note: don't set setsResult if the function returns VOID, as evidenced
  	 * by not having made a junkfilter.  This ensures we'll throw away any
  	 * output from a utility statement that check_sql_fn_retval deemed to not
  	 * have output.
  	 */
  	if (lasttages && fcache->junkFilter)
  	{
  		lasttages->setsResult = true;
  		if (lazyEvalOK &&
  			lasttages->stmt->commandType == CMD_SELECT &&
  			!lasttages->stmt->hasModifyingCTE)
  			fcache->lazyEval = lasttages->lazyEval = true;
  	}
  
  	return eslist;
  }
  
  /*
   * Initialize the SQLFunctionCache for a SQL function
   */
  static void
  init_sql_fcache(FmgrInfo *finfo, Oid collation, bool lazyEvalOK)
  {
  	Oid			foid = finfo->fn_oid;
  	MemoryContext fcontext;
  	MemoryContext oldcontext;
  	Oid			rettype;
  	HeapTuple	procedureTuple;
  	Form_pg_proc procedureStruct;
  	SQLFunctionCachePtr fcache;
  	List	   *raw_parsetree_list;
  	List	   *queryTree_list;
  	List	   *flat_query_list;
  	ListCell   *lc;
  	Datum		tmp;
  	bool		isNull;
  
  	/*
  	 * Create memory context that holds all the SQLFunctionCache data.  It
  	 * must be a child of whatever context holds the FmgrInfo.
  	 */
  	fcontext = AllocSetContextCreate(finfo->fn_mcxt,
  									 "SQL function data",
  									 ALLOCSET_DEFAULT_SIZES);
  
  	oldcontext = MemoryContextSwitchTo(fcontext);
  
  	/*
  	 * Create the struct proper, link it to fcontext and fn_extra.  Once this
  	 * is done, we'll be able to recover the memory after failure, even if the
  	 * FmgrInfo is long-lived.
  	 */
  	fcache = (SQLFunctionCachePtr) palloc0(sizeof(SQLFunctionCache));
  	fcache->fcontext = fcontext;
  	finfo->fn_extra = (void *) fcache;
  
  	/*
  	 * get the procedure tuple corresponding to the given function Oid
  	 */
  	procedureTuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(foid));
  	if (!HeapTupleIsValid(procedureTuple))
  		elog(ERROR, "cache lookup failed for function %u", foid);
  	procedureStruct = (Form_pg_proc) GETSTRUCT(procedureTuple);
  
  	/*
  	 * copy function name immediately for use by error reporting callback
  	 */
  	fcache->fname = pstrdup(NameStr(procedureStruct->proname));
  
  	/*
  	 * get the result type from the procedure tuple, and check for polymorphic
  	 * result type; if so, find out the actual result type.
  	 */
  	rettype = procedureStruct->prorettype;
  
  	if (IsPolymorphicType(rettype))
  	{
  		rettype = get_fn_expr_rettype(finfo);
  		if (rettype == InvalidOid)	/* this probably should not happen */
  			ereport(ERROR,
  					(errcode(ERRCODE_DATATYPE_MISMATCH),
  					 errmsg("could not determine actual result type for function declared to return type %s",
  							format_type_be(procedureStruct->prorettype))));
  	}
  
  	fcache->rettype = rettype;
  
  	/* Fetch the typlen and byval info for the result type */
  	get_typlenbyval(rettype, &fcache->typlen, &fcache->typbyval);
  
  	/* Remember whether we're returning setof something */
  	fcache->returnsSet = procedureStruct->proretset;
  
  	/* Remember if function is STABLE/IMMUTABLE */
  	fcache->readonly_func =
  		(procedureStruct->provolatile != PROVOLATILE_VOLATILE);
  
  	/*
  	 * We need the actual argument types to pass to the parser.  Also make
  	 * sure that parameter symbols are considered to have the function's
  	 * resolved input collation.
  	 */
  	fcache->pinfo = prepare_sql_fn_parse_info(procedureTuple,
  											  finfo->fn_expr,
  											  collation);
  
  	/*
  	 * And of course we need the function body text.
  	 */
  	tmp = SysCacheGetAttr(PROCOID,
  						  procedureTuple,
  						  Anum_pg_proc_prosrc,
  						  &isNull);
  	if (isNull)
  		elog(ERROR, "null prosrc for function %u", foid);
  	fcache->src = TextDatumGetCString(tmp);
  
  	/*
  	 * Parse and rewrite the queries in the function text.  Use sublists to
  	 * keep track of the original query boundaries.  But we also build a
  	 * "flat" list of the rewritten queries to pass to check_sql_fn_retval.
  	 * This is because the last canSetTag query determines the result type
  	 * independently of query boundaries --- and it might not be in the last
  	 * sublist, for example if the last query rewrites to DO INSTEAD NOTHING.
  	 * (It might not be unreasonable to throw an error in such a case, but
  	 * this is the historical behavior and it doesn't seem worth changing.)
  	 *
  	 * Note: since parsing and planning is done in fcontext, we will generate
  	 * a lot of cruft that lives as long as the fcache does.  This is annoying
  	 * but we'll not worry about it until the module is rewritten to use
  	 * plancache.c.
  	 */
  	raw_parsetree_list = pg_parse_query(fcache->src);
  
  	queryTree_list = NIL;
  	flat_query_list = NIL;
  	foreach(lc, raw_parsetree_list)
  	{
  		RawStmt    *parsetree = lfirst_node(RawStmt, lc);
  		List	   *queryTree_sublist;
  
  		queryTree_sublist = pg_analyze_and_rewrite_params(parsetree,
  														  fcache->src,
  														  (ParserSetupHook) sql_fn_parser_setup,
  														  fcache->pinfo,
  														  NULL);
  		queryTree_list = lappend(queryTree_list, queryTree_sublist);
  		flat_query_list = list_concat(flat_query_list,
  									  list_copy(queryTree_sublist));
  	}
  
  	/*
  	 * Check that the function returns the type it claims to.  Although in
  	 * simple cases this was already done when the function was defined, we
  	 * have to recheck because database objects used in the function's queries
  	 * might have changed type.  We'd have to do it anyway if the function had
  	 * any polymorphic arguments.
  	 *
  	 * Note: we set fcache->returnsTuple according to whether we are returning
  	 * the whole tuple result or just a single column.  In the latter case we
  	 * clear returnsTuple because we need not act different from the scalar
  	 * result case, even if it's a rowtype column.  (However, we have to force
  	 * lazy eval mode in that case; otherwise we'd need extra code to expand
  	 * the rowtype column into multiple columns, since we have no way to
  	 * notify the caller that it should do that.)
  	 *
  	 * check_sql_fn_retval will also construct a JunkFilter we can use to
  	 * coerce the returned rowtype to the desired form (unless the result type
  	 * is VOID, in which case there's nothing to coerce to).
  	 */
  	fcache->returnsTuple = check_sql_fn_retval(foid,
  											   rettype,
  											   flat_query_list,
  											   NULL,
  											   &fcache->junkFilter);
  
  	if (fcache->returnsTuple)
  	{
  		/* Make sure output rowtype is properly blessed */
  		BlessTupleDesc(fcache->junkFilter->jf_resultSlot->tts_tupleDescriptor);
  	}
  	else if (fcache->returnsSet && type_is_rowtype(fcache->rettype))
  	{
  		/*
  		 * Returning rowtype as if it were scalar --- materialize won't work.
  		 * Right now it's sufficient to override any caller preference for
  		 * materialize mode, but to add more smarts in init_execution_state
  		 * about this, we'd probably need a three-way flag instead of bool.
  		 */
  		lazyEvalOK = true;
  	}
  
  	/* Finally, plan the queries */
  	fcache->func_state = init_execution_state(queryTree_list,
  											  fcache,
  											  lazyEvalOK);
  
  	/* Mark fcache with time of creation to show it's valid */
  	fcache->lxid = MyProc->lxid;
  	fcache->subxid = GetCurrentSubTransactionId();
  
  	ReleaseSysCache(procedureTuple);
  
  	MemoryContextSwitchTo(oldcontext);
  }
  
  /* Start up execution of one execution_state node */
  static void
  postquel_start(execution_state *es, SQLFunctionCachePtr fcache)
  {
  	DestReceiver *dest;
  
  	Assert(es->qd == NULL);
  
  	/* Caller should have ensured a suitable snapshot is active */
  	Assert(ActiveSnapshotSet());
  
  	/*
  	 * If this query produces the function result, send its output to the
  	 * tuplestore; else discard any output.
  	 */
  	if (es->setsResult)
  	{
  		DR_sqlfunction *myState;
  
  		dest = CreateDestReceiver(DestSQLFunction);
  		/* pass down the needed info to the dest receiver routines */
  		myState = (DR_sqlfunction *) dest;
  		Assert(myState->pub.mydest == DestSQLFunction);
  		myState->tstore = fcache->tstore;
  		myState->cxt = CurrentMemoryContext;
  		myState->filter = fcache->junkFilter;
  	}
  	else
  		dest = None_Receiver;
  
  	es->qd = CreateQueryDesc(es->stmt,
  							 fcache->src,
  							 GetActiveSnapshot(),
  							 InvalidSnapshot,
  							 dest,
  							 fcache->paramLI,
  							 es->qd ? es->qd->queryEnv : NULL,
  							 0);
  
  	/* Utility commands don't need Executor. */
  	if (es->qd->operation != CMD_UTILITY)
  	{
  		/*
  		 * In lazyEval mode, do not let the executor set up an AfterTrigger
  		 * context.  This is necessary not just an optimization, because we
  		 * mustn't exit from the function execution with a stacked
  		 * AfterTrigger level still active.  We are careful not to select
  		 * lazyEval mode for any statement that could possibly queue triggers.
  		 */
  		int			eflags;
  
  		if (es->lazyEval)
  			eflags = EXEC_FLAG_SKIP_TRIGGERS;
  		else
  			eflags = 0;			/* default run-to-completion flags */
  		ExecutorStart(es->qd, eflags);
  	}
  
  	es->status = F_EXEC_RUN;
  }
  
  /* Run one execution_state; either to completion or to first result row */
  /* Returns true if we ran to completion */
  static bool
  postquel_getnext(execution_state *es, SQLFunctionCachePtr fcache)
  {
  	bool		result;
  
  	if (es->qd->operation == CMD_UTILITY)
  	{
  		ProcessUtility(es->qd->plannedstmt,
  					   fcache->src,
  					   PROCESS_UTILITY_QUERY,
  					   es->qd->params,
  					   es->qd->queryEnv,
  					   es->qd->dest,
  					   NULL);
  		result = true;			/* never stops early */
  	}
  	else
  	{
  		/* Run regular commands to completion unless lazyEval */
  		uint64		count = (es->lazyEval) ? 1 : 0;
  
  		ExecutorRun(es->qd, ForwardScanDirection, count, !fcache->returnsSet || !es->lazyEval);
  
  		/*
  		 * If we requested run to completion OR there was no tuple returned,
  		 * command must be complete.
  		 */
  		result = (count == 0 || es->qd->estate->es_processed == 0);
  	}
  
  	return result;
  }
  
  /* Shut down execution of one execution_state node */
  static void
  postquel_end(execution_state *es)
  {
  	/* mark status done to ensure we don't do ExecutorEnd twice */
  	es->status = F_EXEC_DONE;
  
  	/* Utility commands don't need Executor. */
  	if (es->qd->operation != CMD_UTILITY)
  	{
  		ExecutorFinish(es->qd);
  		ExecutorEnd(es->qd);
  	}
  
  	(*es->qd->dest->rDestroy) (es->qd->dest);
  
  	FreeQueryDesc(es->qd);
  	es->qd = NULL;
  }
  
  /* Build ParamListInfo array representing current arguments */
  static void
  postquel_sub_params(SQLFunctionCachePtr fcache,
  					FunctionCallInfo fcinfo)
  {
  	int			nargs = fcinfo->nargs;
  
  	if (nargs > 0)
  	{
  		ParamListInfo paramLI;
  		int			i;
  
  		if (fcache->paramLI == NULL)
  		{
  			paramLI = (ParamListInfo)
  				palloc(offsetof(ParamListInfoData, params) +
  					   nargs * sizeof(ParamExternData));
  			/* we have static list of params, so no hooks needed */
  			paramLI->paramFetch = NULL;
  			paramLI->paramFetchArg = NULL;
  			paramLI->parserSetup = NULL;
  			paramLI->parserSetupArg = NULL;
  			paramLI->numParams = nargs;
  			paramLI->paramMask = NULL;
  			fcache->paramLI = paramLI;
  		}
  		else
  		{
  			paramLI = fcache->paramLI;
  			Assert(paramLI->numParams == nargs);
  		}
  
  		for (i = 0; i < nargs; i++)
  		{
  			ParamExternData *prm = &paramLI->params[i];
  
  			prm->value = fcinfo->arg[i];
  			prm->isnull = fcinfo->argnull[i];
  			prm->pflags = 0;
  			prm->ptype = fcache->pinfo->argtypes[i];
  		}
  	}
  	else
  		fcache->paramLI = NULL;
  }
  
  /*
   * Extract the SQL function's value from a single result row.  This is used
   * both for scalar (non-set) functions and for each row of a lazy-eval set
   * result.
   */
  static Datum
  postquel_get_single_result(TupleTableSlot *slot,
  						   FunctionCallInfo fcinfo,
  						   SQLFunctionCachePtr fcache,
  						   MemoryContext resultcontext)
  {
  	Datum		value;
  	MemoryContext oldcontext;
  
  	/*
  	 * Set up to return the function value.  For pass-by-reference datatypes,
  	 * be sure to allocate the result in resultcontext, not the current memory
  	 * context (which has query lifespan).  We can't leave the data in the
  	 * TupleTableSlot because we intend to clear the slot before returning.
  	 */
  	oldcontext = MemoryContextSwitchTo(resultcontext);
  
  	if (fcache->returnsTuple)
  	{
  		/* We must return the whole tuple as a Datum. */
  		fcinfo->isnull = false;
  		value = ExecFetchSlotTupleDatum(slot);
  	}
  	else
  	{
  		/*
  		 * Returning a scalar, which we have to extract from the first column
  		 * of the SELECT result, and then copy into result context if needed.
  		 */
  		value = slot_getattr(slot, 1, &(fcinfo->isnull));
  
  		if (!fcinfo->isnull)
  			value = datumCopy(value, fcache->typbyval, fcache->typlen);
  	}
  
  	MemoryContextSwitchTo(oldcontext);
  
  	return value;
  }
  
  /*
   * fmgr_sql: function call manager for SQL functions
   */
  Datum
  fmgr_sql(PG_FUNCTION_ARGS)
  {
  	SQLFunctionCachePtr fcache;
  	ErrorContextCallback sqlerrcontext;
  	MemoryContext oldcontext;
  	bool		randomAccess;
  	bool		lazyEvalOK;
  	bool		is_first;
  	bool		pushed_snapshot;
  	execution_state *es;
  	TupleTableSlot *slot;
  	Datum		result;
  	List	   *eslist;
  	ListCell   *eslc;
  
  	/*
  	 * Setup error traceback support for ereport()
  	 */
  	sqlerrcontext.callback = sql_exec_error_callback;
  	sqlerrcontext.arg = fcinfo->flinfo;
  	sqlerrcontext.previous = error_context_stack;
  	error_context_stack = &sqlerrcontext;
  
  	/* Check call context */
  	if (fcinfo->flinfo->fn_retset)
  	{
  		ReturnSetInfo *rsi = (ReturnSetInfo *) fcinfo->resultinfo;
  
  		/*
  		 * For simplicity, we require callers to support both set eval modes.
  		 * There are cases where we must use one or must use the other, and
  		 * it's not really worthwhile to postpone the check till we know. But
  		 * note we do not require caller to provide an expectedDesc.
  		 */
  		if (!rsi || !IsA(rsi, ReturnSetInfo) ||
  			(rsi->allowedModes & SFRM_ValuePerCall) == 0 ||
  			(rsi->allowedModes & SFRM_Materialize) == 0)
  			ereport(ERROR,
  					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  					 errmsg("set-valued function called in context that cannot accept a set")));
  		randomAccess = rsi->allowedModes & SFRM_Materialize_Random;
  		lazyEvalOK = !(rsi->allowedModes & SFRM_Materialize_Preferred);
  	}
  	else
  	{
  		randomAccess = false;
  		lazyEvalOK = true;
  	}
  
  	/*
  	 * Initialize fcache (build plans) if first time through; or re-initialize
  	 * if the cache is stale.
  	 */
  	fcache = (SQLFunctionCachePtr) fcinfo->flinfo->fn_extra;
  
  	if (fcache != NULL)
  	{
  		if (fcache->lxid != MyProc->lxid ||
  			!SubTransactionIsActive(fcache->subxid))
  		{
  			/* It's stale; unlink and delete */
  			fcinfo->flinfo->fn_extra = NULL;
  			MemoryContextDelete(fcache->fcontext);
  			fcache = NULL;
  		}
  	}
  
  	if (fcache == NULL)
  	{
  		init_sql_fcache(fcinfo->flinfo, PG_GET_COLLATION(), lazyEvalOK);
  		fcache = (SQLFunctionCachePtr) fcinfo->flinfo->fn_extra;
  	}
  
  	/*
  	 * Switch to context in which the fcache lives.  This ensures that our
  	 * tuplestore etc will have sufficient lifetime.  The sub-executor is
  	 * responsible for deleting per-tuple information.  (XXX in the case of a
  	 * long-lived FmgrInfo, this policy represents more memory leakage, but
  	 * it's not entirely clear where to keep stuff instead.)
  	 */
  	oldcontext = MemoryContextSwitchTo(fcache->fcontext);
  
  	/*
  	 * Find first unfinished query in function, and note whether it's the
  	 * first query.
  	 */
  	eslist = fcache->func_state;
  	es = NULL;
  	is_first = true;
  	foreach(eslc, eslist)
  	{
  		es = (execution_state *) lfirst(eslc);
  
  		while (es && es->status == F_EXEC_DONE)
  		{
  			is_first = false;
  			es = es->next;
  		}
  
  		if (es)
  			break;
  	}
  
  	/*
  	 * Convert params to appropriate format if starting a fresh execution. (If
  	 * continuing execution, we can re-use prior params.)
  	 */
  	if (is_first && es && es->status == F_EXEC_START)
  		postquel_sub_params(fcache, fcinfo);
  
  	/*
  	 * Build tuplestore to hold results, if we don't have one already. Note
  	 * it's in the query-lifespan context.
  	 */
  	if (!fcache->tstore)
  		fcache->tstore = tuplestore_begin_heap(randomAccess, false, work_mem);
  
  	/*
  	 * Execute each command in the function one after another until we either
  	 * run out of commands or get a result row from a lazily-evaluated SELECT.
  	 *
  	 * Notes about snapshot management:
  	 *
  	 * In a read-only function, we just use the surrounding query's snapshot.
  	 *
  	 * In a non-read-only function, we rely on the fact that we'll never
  	 * suspend execution between queries of the function: the only reason to
  	 * suspend execution before completion is if we are returning a row from a
  	 * lazily-evaluated SELECT.  So, when first entering this loop, we'll
  	 * either start a new query (and push a fresh snapshot) or re-establish
  	 * the active snapshot from the existing query descriptor.  If we need to
  	 * start a new query in a subsequent execution of the loop, either we need
  	 * a fresh snapshot (and pushed_snapshot is false) or the existing
  	 * snapshot is on the active stack and we can just bump its command ID.
  	 */
  	pushed_snapshot = false;
  	while (es)
  	{
  		bool		completed;
  
  		if (es->status == F_EXEC_START)
  		{
  			/*
  			 * If not read-only, be sure to advance the command counter for
  			 * each command, so that all work to date in this transaction is
  			 * visible.  Take a new snapshot if we don't have one yet,
  			 * otherwise just bump the command ID in the existing snapshot.
  			 */
  			if (!fcache->readonly_func)
  			{
  				CommandCounterIncrement();
  				if (!pushed_snapshot)
  				{
  					PushActiveSnapshot(GetTransactionSnapshot());
  					pushed_snapshot = true;
  				}
  				else
  					UpdateActiveSnapshotCommandId();
  			}
  
  			postquel_start(es, fcache);
  		}
  		else if (!fcache->readonly_func && !pushed_snapshot)
  		{
  			/* Re-establish active snapshot when re-entering function */
  			PushActiveSnapshot(es->qd->snapshot);
  			pushed_snapshot = true;
  		}
  
  		completed = postquel_getnext(es, fcache);
  
  		/*
  		 * If we ran the command to completion, we can shut it down now. Any
  		 * row(s) we need to return are safely stashed in the tuplestore, and
  		 * we want to be sure that, for example, AFTER triggers get fired
  		 * before we return anything.  Also, if the function doesn't return
  		 * set, we can shut it down anyway because it must be a SELECT and we
  		 * don't care about fetching any more result rows.
  		 */
  		if (completed || !fcache->returnsSet)
  			postquel_end(es);
  
  		/*
  		 * Break from loop if we didn't shut down (implying we got a
  		 * lazily-evaluated row).  Otherwise we'll press on till the whole
  		 * function is done, relying on the tuplestore to keep hold of the
  		 * data to eventually be returned.  This is necessary since an
  		 * INSERT/UPDATE/DELETE RETURNING that sets the result might be
  		 * followed by additional rule-inserted commands, and we want to
  		 * finish doing all those commands before we return anything.
  		 */
  		if (es->status != F_EXEC_DONE)
  			break;
  
  		/*
  		 * Advance to next execution_state, which might be in the next list.
  		 */
  		es = es->next;
  		while (!es)
  		{
  			eslc = lnext(eslc);
  			if (!eslc)
  				break;			/* end of function */
  
  			es = (execution_state *) lfirst(eslc);
  
  			/*
  			 * Flush the current snapshot so that we will take a new one for
  			 * the new query list.  This ensures that new snaps are taken at
  			 * original-query boundaries, matching the behavior of interactive
  			 * execution.
  			 */
  			if (pushed_snapshot)
  			{
  				PopActiveSnapshot();
  				pushed_snapshot = false;
  			}
  		}
  	}
  
  	/*
  	 * The tuplestore now contains whatever row(s) we are supposed to return.
  	 */
  	if (fcache->returnsSet)
  	{
  		ReturnSetInfo *rsi = (ReturnSetInfo *) fcinfo->resultinfo;
  
  		if (es)
  		{
  			/*
  			 * If we stopped short of being done, we must have a lazy-eval
  			 * row.
  			 */
  			Assert(es->lazyEval);
  			/* Re-use the junkfilter's output slot to fetch back the tuple */
  			Assert(fcache->junkFilter);
  			slot = fcache->junkFilter->jf_resultSlot;
  			if (!tuplestore_gettupleslot(fcache->tstore, true, false, slot))
  				elog(ERROR, "failed to fetch lazy-eval tuple");
  			/* Extract the result as a datum, and copy out from the slot */
  			result = postquel_get_single_result(slot, fcinfo,
  												fcache, oldcontext);
  			/* Clear the tuplestore, but keep it for next time */
  			/* NB: this might delete the slot's content, but we don't care */
  			tuplestore_clear(fcache->tstore);
  
  			/*
  			 * Let caller know we're not finished.
  			 */
  			rsi->isDone = ExprMultipleResult;
  
  			/*
  			 * Ensure we will get shut down cleanly if the exprcontext is not
  			 * run to completion.
  			 */
  			if (!fcache->shutdown_reg)
  			{
  				RegisterExprContextCallback(rsi->econtext,
  											ShutdownSQLFunction,
  											PointerGetDatum(fcache));
  				fcache->shutdown_reg = true;
  			}
  		}
  		else if (fcache->lazyEval)
  		{
  			/*
  			 * We are done with a lazy evaluation.  Clean up.
  			 */
  			tuplestore_clear(fcache->tstore);
  
  			/*
  			 * Let caller know we're finished.
  			 */
  			rsi->isDone = ExprEndResult;
  
  			fcinfo->isnull = true;
  			result = (Datum) 0;
  
  			/* Deregister shutdown callback, if we made one */
  			if (fcache->shutdown_reg)
  			{
  				UnregisterExprContextCallback(rsi->econtext,
  											  ShutdownSQLFunction,
  											  PointerGetDatum(fcache));
  				fcache->shutdown_reg = false;
  			}
  		}
  		else
  		{
  			/*
  			 * We are done with a non-lazy evaluation.  Return whatever is in
  			 * the tuplestore.  (It is now caller's responsibility to free the
  			 * tuplestore when done.)
  			 */
  			rsi->returnMode = SFRM_Materialize;
  			rsi->setResult = fcache->tstore;
  			fcache->tstore = NULL;
  			/* must copy desc because execSRF.c will free it */
  			if (fcache->junkFilter)
  				rsi->setDesc = CreateTupleDescCopy(fcache->junkFilter->jf_cleanTupType);
  
  			fcinfo->isnull = true;
  			result = (Datum) 0;
  
  			/* Deregister shutdown callback, if we made one */
  			if (fcache->shutdown_reg)
  			{
  				UnregisterExprContextCallback(rsi->econtext,
  											  ShutdownSQLFunction,
  											  PointerGetDatum(fcache));
  				fcache->shutdown_reg = false;
  			}
  		}
  	}
  	else
  	{
  		/*
  		 * Non-set function.  If we got a row, return it; else return NULL.
  		 */
  		if (fcache->junkFilter)
  		{
  			/* Re-use the junkfilter's output slot to fetch back the tuple */
  			slot = fcache->junkFilter->jf_resultSlot;
  			if (tuplestore_gettupleslot(fcache->tstore, true, false, slot))
  				result = postquel_get_single_result(slot, fcinfo,
  													fcache, oldcontext);
  			else
  			{
  				fcinfo->isnull = true;
  				result = (Datum) 0;
  			}
  		}
  		else
  		{
  			/* Should only get here for VOID functions */
  			Assert(fcache->rettype == VOIDOID);
  			fcinfo->isnull = true;
  			result = (Datum) 0;
  		}
  
  		/* Clear the tuplestore, but keep it for next time */
  		tuplestore_clear(fcache->tstore);
  	}
  
  	/* Pop snapshot if we have pushed one */
  	if (pushed_snapshot)
  		PopActiveSnapshot();
  
  	/*
  	 * If we've gone through every command in the function, we are done. Reset
  	 * the execution states to start over again on next call.
  	 */
  	if (es == NULL)
  	{
  		foreach(eslc, fcache->func_state)
  		{
  			es = (execution_state *) lfirst(eslc);
  			while (es)
  			{
  				es->status = F_EXEC_START;
  				es = es->next;
  			}
  		}
  	}
  
  	error_context_stack = sqlerrcontext.previous;
  
  	MemoryContextSwitchTo(oldcontext);
  
  	return result;
  }
  
  
  /*
   * error context callback to let us supply a call-stack traceback
   */
  static void
  sql_exec_error_callback(void *arg)
  {
  	FmgrInfo   *flinfo = (FmgrInfo *) arg;
  	SQLFunctionCachePtr fcache = (SQLFunctionCachePtr) flinfo->fn_extra;
  	int			syntaxerrposition;
  
  	/*
  	 * We can do nothing useful if init_sql_fcache() didn't get as far as
  	 * saving the function name
  	 */
  	if (fcache == NULL || fcache->fname == NULL)
  		return;
  
  	/*
  	 * If there is a syntax error position, convert to internal syntax error
  	 */
  	syntaxerrposition = geterrposition();
  	if (syntaxerrposition > 0 && fcache->src != NULL)
  	{
  		errposition(0);
  		internalerrposition(syntaxerrposition);
  		internalerrquery(fcache->src);
  	}
  
  	/*
  	 * Try to determine where in the function we failed.  If there is a query
  	 * with non-null QueryDesc, finger it.  (We check this rather than looking
  	 * for F_EXEC_RUN state, so that errors during ExecutorStart or
  	 * ExecutorEnd are blamed on the appropriate query; see postquel_start and
  	 * postquel_end.)
  	 */
  	if (fcache->func_state)
  	{
  		execution_state *es;
  		int			query_num;
  		ListCell   *lc;
  
  		es = NULL;
  		query_num = 1;
  		foreach(lc, fcache->func_state)
  		{
  			es = (execution_state *) lfirst(lc);
  			while (es)
  			{
  				if (es->qd)
  				{
  					errcontext("SQL function \"%s\" statement %d",
  							   fcache->fname, query_num);
  					break;
  				}
  				es = es->next;
  			}
  			if (es)
  				break;
  			query_num++;
  		}
  		if (es == NULL)
  		{
  			/*
  			 * couldn't identify a running query; might be function entry,
  			 * function exit, or between queries.
  			 */
  			errcontext("SQL function \"%s\"", fcache->fname);
  		}
  	}
  	else
  	{
  		/*
  		 * Assume we failed during init_sql_fcache().  (It's possible that the
  		 * function actually has an empty body, but in that case we may as
  		 * well report all errors as being "during startup".)
  		 */
  		errcontext("SQL function \"%s\" during startup", fcache->fname);
  	}
  }
  
  
  /*
   * callback function in case a function-returning-set needs to be shut down
   * before it has been run to completion
   */
  static void
  ShutdownSQLFunction(Datum arg)
  {
  	SQLFunctionCachePtr fcache = (SQLFunctionCachePtr) DatumGetPointer(arg);
  	execution_state *es;
  	ListCell   *lc;
  
  	foreach(lc, fcache->func_state)
  	{
  		es = (execution_state *) lfirst(lc);
  		while (es)
  		{
  			/* Shut down anything still running */
  			if (es->status == F_EXEC_RUN)
  			{
  				/* Re-establish active snapshot for any called functions */
  				if (!fcache->readonly_func)
  					PushActiveSnapshot(es->qd->snapshot);
  
  				postquel_end(es);
  
  				if (!fcache->readonly_func)
  					PopActiveSnapshot();
  			}
  
  			/* Reset states to START in case we're called again */
  			es->status = F_EXEC_START;
  			es = es->next;
  		}
  	}
  
  	/* Release tuplestore if we have one */
  	if (fcache->tstore)
  		tuplestore_end(fcache->tstore);
  	fcache->tstore = NULL;
  
  	/* execUtils will deregister the callback... */
  	fcache->shutdown_reg = false;
  }
  
  
  /*
   * check_sql_fn_retval() -- check return value of a list of sql parse trees.
   *
   * The return value of a sql function is the value returned by the last
   * canSetTag query in the function.  We do some ad-hoc type checking here
   * to be sure that the user is returning the type he claims.  There are
   * also a couple of strange-looking features to assist callers in dealing
   * with allowed special cases, such as binary-compatible result types.
   *
   * For a polymorphic function the passed rettype must be the actual resolved
   * output type of the function; we should never see a polymorphic pseudotype
   * such as ANYELEMENT as rettype.  (This means we can't check the type during
   * function definition of a polymorphic function.)
   *
   * This function returns true if the sql function returns the entire tuple
   * result of its final statement, or false if it returns just the first column
   * result of that statement.  It throws an error if the final statement doesn't
   * return the right type at all.
   *
   * Note that because we allow "SELECT rowtype_expression", the result can be
   * false even when the declared function return type is a rowtype.
   *
   * If modifyTargetList isn't NULL, the function will modify the final
   * statement's targetlist in two cases:
   * (1) if the tlist returns values that are binary-coercible to the expected
   * type rather than being exactly the expected type.  RelabelType nodes will
   * be inserted to make the result types match exactly.
   * (2) if there are dropped columns in the declared result rowtype.  NULL
   * output columns will be inserted in the tlist to match them.
   * (Obviously the caller must pass a parsetree that is okay to modify when
   * using this flag.)  Note that this flag does not affect whether the tlist is
   * considered to be a legal match to the result type, only how we react to
   * allowed not-exact-match cases.  *modifyTargetList will be set true iff
   * we had to make any "dangerous" changes that could modify the semantics of
   * the statement.  If it is set true, the caller should not use the modified
   * statement, but for simplicity we apply the changes anyway.
   *
   * If junkFilter isn't NULL, then *junkFilter is set to a JunkFilter defined
   * to convert the function's tuple result to the correct output tuple type.
   * Exception: if the function is defined to return VOID then *junkFilter is
   * set to NULL.
   */
  bool
  check_sql_fn_retval(Oid func_id, Oid rettype, List *queryTreeList,
  					bool *modifyTargetList,
  					JunkFilter **junkFilter)
  {
  	Query	   *parse;
  	List	  **tlist_ptr;
  	List	   *tlist;
  	int			tlistlen;
  	char		fn_typtype;
  	Oid			restype;
  	ListCell   *lc;
  
  	AssertArg(!IsPolymorphicType(rettype));
  
  	if (modifyTargetList)
  		*modifyTargetList = false;	/* initialize for no change */
  	if (junkFilter)
  		*junkFilter = NULL;		/* initialize in case of VOID result */
  
  	/*
  	 * Find the last canSetTag query in the list.  This isn't necessarily the
  	 * last parsetree, because rule rewriting can insert queries after what
  	 * the user wrote.
  	 */
  	parse = NULL;
  	foreach(lc, queryTreeList)
  	{
  		Query	   *q = lfirst_node(Query, lc);
  
  		if (q->canSetTag)
  			parse = q;
  	}
  
  	/*
  	 * If it's a plain SELECT, it returns whatever the targetlist says.
  	 * Otherwise, if it's INSERT/UPDATE/DELETE with RETURNING, it returns
  	 * that. Otherwise, the function return type must be VOID.
  	 *
  	 * Note: eventually replace this test with QueryReturnsTuples?	We'd need
  	 * a more general method of determining the output type, though.  Also, it
  	 * seems too dangerous to consider FETCH or EXECUTE as returning a
  	 * determinable rowtype, since they depend on relatively short-lived
  	 * entities.
  	 */
  	if (parse &&
  		parse->commandType == CMD_SELECT)
  	{
  		tlist_ptr = &parse->targetList;
  		tlist = parse->targetList;
  	}
  	else if (parse &&
  			 (parse->commandType == CMD_INSERT ||
  			  parse->commandType == CMD_UPDATE ||
  			  parse->commandType == CMD_DELETE) &&
  			 parse->returningList)
  	{
  		tlist_ptr = &parse->returningList;
  		tlist = parse->returningList;
  	}
  	else
  	{
  		/* Empty function body, or last statement is a utility command */
  		if (rettype != VOIDOID)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
  					 errmsg("return type mismatch in function declared to return %s",
  							format_type_be(rettype)),
  					 errdetail("Function's final statement must be SELECT or INSERT/UPDATE/DELETE RETURNING.")));
  		return false;
  	}
  
  	/*
  	 * OK, check that the targetlist returns something matching the declared
  	 * type.  (We used to insist that the declared type not be VOID in this
  	 * case, but that makes it hard to write a void function that exits after
  	 * calling another void function.  Instead, we insist that the tlist
  	 * return void ... so void is treated as if it were a scalar type below.)
  	 */
  
  	/*
  	 * Count the non-junk entries in the result targetlist.
  	 */
  	tlistlen = ExecCleanTargetListLength(tlist);
  
  	fn_typtype = get_typtype(rettype);
  
  	if (fn_typtype == TYPTYPE_BASE ||
  		fn_typtype == TYPTYPE_DOMAIN ||
  		fn_typtype == TYPTYPE_ENUM ||
  		fn_typtype == TYPTYPE_RANGE ||
  		rettype == VOIDOID)
  	{
  		/*
  		 * For scalar-type returns, the target list must have exactly one
  		 * non-junk entry, and its type must agree with what the user
  		 * declared; except we allow binary-compatible types too.
  		 */
  		TargetEntry *tle;
  
  		if (tlistlen != 1)
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
  					 errmsg("return type mismatch in function declared to return %s",
  							format_type_be(rettype)),
  					 errdetail("Final statement must return exactly one column.")));
  
  		/* We assume here that non-junk TLEs must come first in tlists */
  		tle = (TargetEntry *) linitial(tlist);
  		Assert(!tle->resjunk);
  
  		restype = exprType((Node *) tle->expr);
  		if (!IsBinaryCoercible(restype, rettype))
  			ereport(ERROR,
  					(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
  					 errmsg("return type mismatch in function declared to return %s",
  							format_type_be(rettype)),
  					 errdetail("Actual return type is %s.",
  							   format_type_be(restype))));
  		if (modifyTargetList && restype != rettype)
  		{
  			tle->expr = (Expr *) makeRelabelType(tle->expr,
  												 rettype,
  												 -1,
  												 get_typcollation(rettype),
  												 COERCE_IMPLICIT_CAST);
  			/* Relabel is dangerous if TLE is a sort/group or setop column */
  			if (tle->ressortgroupref != 0 || parse->setOperations)
  				*modifyTargetList = true;
  		}
  
  		/* Set up junk filter if needed */
  		if (junkFilter)
  			*junkFilter = ExecInitJunkFilter(tlist, false, NULL);
  	}
  	else if (fn_typtype == TYPTYPE_COMPOSITE || rettype == RECORDOID)
  	{
  		/* Returns a rowtype */
  		TupleDesc	tupdesc;
  		int			tupnatts;	/* physical number of columns in tuple */
  		int			tuplogcols; /* # of nondeleted columns in tuple */
  		int			colindex;	/* physical column index */
  		List	   *newtlist;	/* new non-junk tlist entries */
  		List	   *junkattrs;	/* new junk tlist entries */
  
  		/*
  		 * If the target list is of length 1, and the type of the varnode in
  		 * the target list matches the declared return type, this is okay.
  		 * This can happen, for example, where the body of the function is
  		 * 'SELECT func2()', where func2 has the same composite return type as
  		 * the function that's calling it.
  		 *
  		 * XXX Note that if rettype is RECORD, the IsBinaryCoercible check
  		 * will succeed for any composite restype.  For the moment we rely on
  		 * runtime type checking to catch any discrepancy, but it'd be nice to
  		 * do better at parse time.
  		 */
  		if (tlistlen == 1)
  		{
  			TargetEntry *tle = (TargetEntry *) linitial(tlist);
  
  			Assert(!tle->resjunk);
  			restype = exprType((Node *) tle->expr);
  			if (IsBinaryCoercible(restype, rettype))
  			{
  				if (modifyTargetList && restype != rettype)
  				{
  					tle->expr = (Expr *) makeRelabelType(tle->expr,
  														 rettype,
  														 -1,
  														 get_typcollation(rettype),
  														 COERCE_IMPLICIT_CAST);
  					/* Relabel is dangerous if sort/group or setop column */
  					if (tle->ressortgroupref != 0 || parse->setOperations)
  						*modifyTargetList = true;
  				}
  				/* Set up junk filter if needed */
  				if (junkFilter)
  					*junkFilter = ExecInitJunkFilter(tlist, false, NULL);
  				return false;	/* NOT returning whole tuple */
  			}
  		}
  
  		/* Is the rowtype fixed, or determined only at runtime? */
  		if (get_func_result_type(func_id, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
  		{
  			/*
  			 * Assume we are returning the whole tuple. Crosschecking against
  			 * what the caller expects will happen at runtime.
  			 */
  			if (junkFilter)
  				*junkFilter = ExecInitJunkFilter(tlist, false, NULL);
  			return true;
  		}
  		Assert(tupdesc);
  
  		/*
  		 * Verify that the targetlist matches the return tuple type. We scan
  		 * the non-deleted attributes to ensure that they match the datatypes
  		 * of the non-resjunk columns.  For deleted attributes, insert NULL
  		 * result columns if the caller asked for that.
  		 */
  		tupnatts = tupdesc->natts;
  		tuplogcols = 0;			/* we'll count nondeleted cols as we go */
  		colindex = 0;
  		newtlist = NIL;			/* these are only used if modifyTargetList */
  		junkattrs = NIL;
  
  		foreach(lc, tlist)
  		{
  			TargetEntry *tle = (TargetEntry *) lfirst(lc);
  			Form_pg_attribute attr;
  			Oid			tletype;
  			Oid			atttype;
  
  			if (tle->resjunk)
  			{
  				if (modifyTargetList)
  					junkattrs = lappend(junkattrs, tle);
  				continue;
  			}
  
  			do
  			{
  				colindex++;
  				if (colindex > tupnatts)
  					ereport(ERROR,
  							(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
  							 errmsg("return type mismatch in function declared to return %s",
  									format_type_be(rettype)),
  							 errdetail("Final statement returns too many columns.")));
  				attr = TupleDescAttr(tupdesc, colindex - 1);
  				if (attr->attisdropped && modifyTargetList)
  				{
  					Expr	   *null_expr;
  
  					/* The type of the null we insert isn't important */
  					null_expr = (Expr *) makeConst(INT4OID,
  												   -1,
  												   InvalidOid,
  												   sizeof(int32),
  												   (Datum) 0,
  												   true,	/* isnull */
  												   true /* byval */ );
  					newtlist = lappend(newtlist,
  									   makeTargetEntry(null_expr,
  													   colindex,
  													   NULL,
  													   false));
  					/* NULL insertion is dangerous in a setop */
  					if (parse->setOperations)
  						*modifyTargetList = true;
  				}
  			} while (attr->attisdropped);
  			tuplogcols++;
  
  			tletype = exprType((Node *) tle->expr);
  			atttype = attr->atttypid;
  			if (!IsBinaryCoercible(tletype, atttype))
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
  						 errmsg("return type mismatch in function declared to return %s",
  								format_type_be(rettype)),
  						 errdetail("Final statement returns %s instead of %s at column %d.",
  								   format_type_be(tletype),
  								   format_type_be(atttype),
  								   tuplogcols)));
  			if (modifyTargetList)
  			{
  				if (tletype != atttype)
  				{
  					tle->expr = (Expr *) makeRelabelType(tle->expr,
  														 atttype,
  														 -1,
  														 get_typcollation(atttype),
  														 COERCE_IMPLICIT_CAST);
  					/* Relabel is dangerous if sort/group or setop column */
  					if (tle->ressortgroupref != 0 || parse->setOperations)
  						*modifyTargetList = true;
  				}
  				tle->resno = colindex;
  				newtlist = lappend(newtlist, tle);
  			}
  		}
  
  		/* remaining columns in tupdesc had better all be dropped */
  		for (colindex++; colindex <= tupnatts; colindex++)
  		{
  			if (!TupleDescAttr(tupdesc, colindex - 1)->attisdropped)
  				ereport(ERROR,
  						(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
  						 errmsg("return type mismatch in function declared to return %s",
  								format_type_be(rettype)),
  						 errdetail("Final statement returns too few columns.")));
  			if (modifyTargetList)
  			{
  				Expr	   *null_expr;
  
  				/* The type of the null we insert isn't important */
  				null_expr = (Expr *) makeConst(INT4OID,
  											   -1,
  											   InvalidOid,
  											   sizeof(int32),
  											   (Datum) 0,
  											   true,	/* isnull */
  											   true /* byval */ );
  				newtlist = lappend(newtlist,
  								   makeTargetEntry(null_expr,
  												   colindex,
  												   NULL,
  												   false));
  				/* NULL insertion is dangerous in a setop */
  				if (parse->setOperations)
  					*modifyTargetList = true;
  			}
  		}
  
  		if (modifyTargetList)
  		{
  			/* ensure resjunk columns are numbered correctly */
  			foreach(lc, junkattrs)
  			{
  				TargetEntry *tle = (TargetEntry *) lfirst(lc);
  
  				tle->resno = colindex++;
  			}
  			/* replace the tlist with the modified one */
  			*tlist_ptr = list_concat(newtlist, junkattrs);
  		}
  
  		/* Set up junk filter if needed */
  		if (junkFilter)
  			*junkFilter = ExecInitJunkFilterConversion(tlist,
  													   CreateTupleDescCopy(tupdesc),
  													   NULL);
  
  		/* Report that we are returning entire tuple result */
  		return true;
  	}
  	else
  		ereport(ERROR,
  				(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
  				 errmsg("return type %s is not supported for SQL functions",
  						format_type_be(rettype))));
  
  	return false;
  }
  
  
  /*
   * CreateSQLFunctionDestReceiver -- create a suitable DestReceiver object
   */
  DestReceiver *
  CreateSQLFunctionDestReceiver(void)
  {
  	DR_sqlfunction *self = (DR_sqlfunction *) palloc0(sizeof(DR_sqlfunction));
  
  	self->pub.receiveSlot = sqlfunction_receive;
  	self->pub.rStartup = sqlfunction_startup;
  	self->pub.rShutdown = sqlfunction_shutdown;
  	self->pub.rDestroy = sqlfunction_destroy;
  	self->pub.mydest = DestSQLFunction;
  
  	/* private fields will be set by postquel_start */
  
  	return (DestReceiver *) self;
  }
  
  /*
   * sqlfunction_startup --- executor startup
   */
  static void
  sqlfunction_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
  {
  	/* no-op */
  }
  
  /*
   * sqlfunction_receive --- receive one tuple
   */
  static bool
  sqlfunction_receive(TupleTableSlot *slot, DestReceiver *self)
  {
  	DR_sqlfunction *myState = (DR_sqlfunction *) self;
  
  	/* Filter tuple as needed */
  	slot = ExecFilterJunk(myState->filter, slot);
  
  	/* Store the filtered tuple into the tuplestore */
  	tuplestore_puttupleslot(myState->tstore, slot);
  
  	return true;
  }
  
  /*
   * sqlfunction_shutdown --- executor end
   */
  static void
  sqlfunction_shutdown(DestReceiver *self)
  {
  	/* no-op */
  }
  
  /*
   * sqlfunction_destroy --- release DestReceiver object
   */
  static void
  sqlfunction_destroy(DestReceiver *self)
  {
  	pfree(self);
  }
  