diff --git a/contrib/dblink/dblink.c b/contrib/dblink/dblink.c
index df1ff05a8fe..46c7cc5923f 100644
--- a/contrib/dblink/dblink.c
+++ b/contrib/dblink/dblink.c
@@ -67,6 +67,7 @@ typedef struct remoteConn
  * Internal declarations
  */
 static Datum dblink_record_internal(FunctionCallInfo fcinfo, bool is_async);
+static void prepTuplestoreResult(FunctionCallInfo fcinfo);
 static void materializeResult(FunctionCallInfo fcinfo, PGresult *res);
 static remoteConn *getConnectionByName(const char *name);
 static HTAB *createConnHash(void);
@@ -495,7 +496,6 @@ PG_FUNCTION_INFO_V1(dblink_fetch);
 Datum
 dblink_fetch(PG_FUNCTION_ARGS)
 {
-	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
 	PGresult   *res = NULL;
 	char	   *conname = NULL;
 	remoteConn *rconn = NULL;
@@ -505,6 +505,8 @@ dblink_fetch(PG_FUNCTION_ARGS)
 	int			howmany = 0;
 	bool		fail = true;	/* default to backward compatible */
 
+	prepTuplestoreResult(fcinfo);
+
 	DBLINK_INIT;
 
 	if (PG_NARGS() == 4)
@@ -551,11 +553,6 @@ dblink_fetch(PG_FUNCTION_ARGS)
 	if (!conn)
 		DBLINK_CONN_NOT_AVAIL;
 
-	/* let the caller know we're sending back a tuplestore */
-	rsinfo->returnMode = SFRM_Materialize;
-	rsinfo->setResult = NULL;
-	rsinfo->setDesc = NULL;
-
 	initStringInfo(&buf);
 	appendStringInfo(&buf, "FETCH %d FROM %s", howmany, curname);
 
@@ -632,7 +629,6 @@ dblink_get_result(PG_FUNCTION_ARGS)
 static Datum
 dblink_record_internal(FunctionCallInfo fcinfo, bool is_async)
 {
-	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
 	char	   *msg;
 	PGresult   *res = NULL;
 	PGconn	   *conn = NULL;
@@ -643,16 +639,7 @@ dblink_record_internal(FunctionCallInfo fcinfo, bool is_async)
 	bool		fail = true;	/* default to backward compatible */
 	bool		freeconn = false;
 
-	/* check to see if caller supports us returning a tuplestore */
-	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("set-valued function called in context that cannot accept a set")));
-	if (!(rsinfo->allowedModes & SFRM_Materialize))
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("materialize mode required, but it is not " \
-						"allowed in this context")));
+	prepTuplestoreResult(fcinfo);
 
 	DBLINK_INIT;
 
@@ -712,11 +699,6 @@ dblink_record_internal(FunctionCallInfo fcinfo, bool is_async)
 	if (!conn)
 		DBLINK_CONN_NOT_AVAIL;
 
-	/* let the caller know we're sending back a tuplestore */
-	rsinfo->returnMode = SFRM_Materialize;
-	rsinfo->setResult = NULL;
-	rsinfo->setDesc = NULL;
-
 	/* synchronous query, or async result retrieval */
 	if (!is_async)
 		res = PQexec(conn, sql);
@@ -745,14 +727,45 @@ dblink_record_internal(FunctionCallInfo fcinfo, bool is_async)
 }
 
 /*
- * Materialize the PGresult to return them as the function result.
- * The res will be released in this function.
+ * Verify function caller can handle a tuplestore result, and set up for that.
+ *
+ * Note: if the caller returns without actually creating a tuplestore, the
+ * executor will treat the function result as an empty set.
+ */
+static void
+prepTuplestoreResult(FunctionCallInfo fcinfo)
+{
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	/* check to see if query supports us returning a tuplestore */
+	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsinfo->allowedModes & SFRM_Materialize))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not allowed in this context")));
+
+	/* let the executor know we're sending back a tuplestore */
+	rsinfo->returnMode = SFRM_Materialize;
+
+	/* caller must fill these to return a non-empty result */
+	rsinfo->setResult = NULL;
+	rsinfo->setDesc = NULL;
+}
+
+/*
+ * Copy the contents of the PGresult into a tuplestore to be returned
+ * as the result of the current function.
+ * The PGresult will be released in this function.
  */
 static void
 materializeResult(FunctionCallInfo fcinfo, PGresult *res)
 {
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
 
+	/* prepTuplestoreResult must have been called previously */
 	Assert(rsinfo->returnMode == SFRM_Materialize);
 
 	PG_TRY();
@@ -1004,85 +1017,97 @@ PG_FUNCTION_INFO_V1(dblink_exec);
 Datum
 dblink_exec(PG_FUNCTION_ARGS)
 {
-	char	   *msg;
-	PGresult   *res = NULL;
-	text	   *sql_cmd_status = NULL;
-	PGconn	   *conn = NULL;
-	char	   *connstr = NULL;
-	char	   *sql = NULL;
-	char	   *conname = NULL;
-	remoteConn *rconn = NULL;
-	bool		freeconn = false;
-	bool		fail = true;	/* default to backward compatible behavior */
+	text	   *volatile sql_cmd_status = NULL;
+	PGconn	   *volatile conn = NULL;
+	volatile bool freeconn = false;
 
 	DBLINK_INIT;
 
-	if (PG_NARGS() == 3)
+	PG_TRY();
 	{
-		/* must be text,text,bool */
-		DBLINK_GET_CONN;
-		sql = text_to_cstring(PG_GETARG_TEXT_PP(1));
-		fail = PG_GETARG_BOOL(2);
-	}
-	else if (PG_NARGS() == 2)
-	{
-		/* might be text,text or text,bool */
-		if (get_fn_expr_argtype(fcinfo->flinfo, 1) == BOOLOID)
+		char	   *msg;
+		PGresult   *res = NULL;
+		char	   *connstr = NULL;
+		char	   *sql = NULL;
+		char	   *conname = NULL;
+		remoteConn *rconn = NULL;
+		bool		fail = true;	/* default to backward compatible behavior */
+
+		if (PG_NARGS() == 3)
 		{
+			/* must be text,text,bool */
+			DBLINK_GET_CONN;
+			sql = text_to_cstring(PG_GETARG_TEXT_PP(1));
+			fail = PG_GETARG_BOOL(2);
+		}
+		else if (PG_NARGS() == 2)
+		{
+			/* might be text,text or text,bool */
+			if (get_fn_expr_argtype(fcinfo->flinfo, 1) == BOOLOID)
+			{
+				conn = pconn->conn;
+				sql = text_to_cstring(PG_GETARG_TEXT_PP(0));
+				fail = PG_GETARG_BOOL(1);
+			}
+			else
+			{
+				DBLINK_GET_CONN;
+				sql = text_to_cstring(PG_GETARG_TEXT_PP(1));
+			}
+		}
+		else if (PG_NARGS() == 1)
+		{
+			/* must be single text argument */
 			conn = pconn->conn;
 			sql = text_to_cstring(PG_GETARG_TEXT_PP(0));
-			fail = PG_GETARG_BOOL(1);
+		}
+		else
+			/* shouldn't happen */
+			elog(ERROR, "wrong number of arguments");
+
+		if (!conn)
+			DBLINK_CONN_NOT_AVAIL;
+
+		res = PQexec(conn, sql);
+		if (!res ||
+			(PQresultStatus(res) != PGRES_COMMAND_OK &&
+			 PQresultStatus(res) != PGRES_TUPLES_OK))
+		{
+			dblink_res_error(conname, res, "could not execute command", fail);
+
+			/*
+			 * and save a copy of the command status string to return as our
+			 * result tuple
+			 */
+			sql_cmd_status = cstring_to_text("ERROR");
+		}
+		else if (PQresultStatus(res) == PGRES_COMMAND_OK)
+		{
+			/*
+			 * and save a copy of the command status string to return as our
+			 * result tuple
+			 */
+			sql_cmd_status = cstring_to_text(PQcmdStatus(res));
+			PQclear(res);
 		}
 		else
 		{
-			DBLINK_GET_CONN;
-			sql = text_to_cstring(PG_GETARG_TEXT_PP(1));
+			PQclear(res);
+			ereport(ERROR,
+				  (errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+				   errmsg("statement returning results not allowed")));
 		}
 	}
-	else if (PG_NARGS() == 1)
+	PG_CATCH();
 	{
-		/* must be single text argument */
-		conn = pconn->conn;
-		sql = text_to_cstring(PG_GETARG_TEXT_PP(0));
+		/* if needed, close the connection to the database */
+		if (freeconn)
+			PQfinish(conn);
+		PG_RE_THROW();
 	}
-	else
-		/* shouldn't happen */
-		elog(ERROR, "wrong number of arguments");
+	PG_END_TRY();
 
-	if (!conn)
-		DBLINK_CONN_NOT_AVAIL;
-
-	res = PQexec(conn, sql);
-	if (!res ||
-		(PQresultStatus(res) != PGRES_COMMAND_OK &&
-		 PQresultStatus(res) != PGRES_TUPLES_OK))
-	{
-		dblink_res_error(conname, res, "could not execute command", fail);
-
-		/*
-		 * and save a copy of the command status string to return as our
-		 * result tuple
-		 */
-		sql_cmd_status = cstring_to_text("ERROR");
-	}
-	else if (PQresultStatus(res) == PGRES_COMMAND_OK)
-	{
-		/*
-		 * and save a copy of the command status string to return as our
-		 * result tuple
-		 */
-		sql_cmd_status = cstring_to_text(PQcmdStatus(res));
-		PQclear(res);
-	}
-	else
-	{
-		PQclear(res);
-		ereport(ERROR,
-				(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
-				 errmsg("statement returning results not allowed")));
-	}
-
-	/* if needed, close the connection to the database and cleanup */
+	/* if needed, close the connection to the database */
 	if (freeconn)
 		PQfinish(conn);
 
@@ -1503,13 +1528,15 @@ dblink_get_notify(PG_FUNCTION_ARGS)
 	MemoryContext per_query_ctx;
 	MemoryContext oldcontext;
 
+	prepTuplestoreResult(fcinfo);
+
 	DBLINK_INIT;
 	if (PG_NARGS() == 1)
 		DBLINK_GET_NAMED_CONN;
 	else
 		conn = pconn->conn;
 
-	/* create the tuplestore */
+	/* create the tuplestore in per-query memory */
 	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
 	oldcontext = MemoryContextSwitchTo(per_query_ctx);
 
@@ -1522,7 +1549,6 @@ dblink_get_notify(PG_FUNCTION_ARGS)
 					   TEXTOID, -1, 0);
 
 	tupstore = tuplestore_begin_heap(true, false, work_mem);
-	rsinfo->returnMode = SFRM_Materialize;
 	rsinfo->setResult = tupstore;
 	rsinfo->setDesc = tupdesc;