Switch some system functions to use get_call_result_type()

This shaves some code by replacing the combinations of
CreateTemplateTupleDesc()/TupleDescInitEntry() hardcoding a mapping of
the attributes listed in pg_proc.dat by get_call_result_type() to build
the TupleDesc needed for the rows generated.

get_call_result_type() is more expensive than the former style, but this
removes some duplication with the lists of OUT parameters (pg_proc.dat
and the attributes hardcoded in these code paths).  This is applied to
functions that are not considered as critical (aka that could be called
repeatedly for monitoring purposes).

Author: Bharath Rupireddy
Reviewed-by: Robert Haas, Álvaro Herrera, Tom Lane, Michael Paquier
Discussion: https://postgr.es/m/CALj2ACV23HW5HP5hFjd89FNS-z5X8r2jNXdMXcpN2BgTtKd87w@mail.gmail.com

contrib/old_snapshot/time_mapping.c

@@ -38,7 +38,6 @@ PG_MODULE_MAGIC;
 PG_FUNCTION_INFO_V1(pg_old_snapshot_time_mapping);
 
 static OldSnapshotTimeMapping *GetOldSnapshotTimeMapping(void);
-static TupleDesc MakeOldSnapshotTimeMappingTupleDesc(void);
 static HeapTuple MakeOldSnapshotTimeMappingTuple(TupleDesc tupdesc,
 												 OldSnapshotTimeMapping *mapping);
 
@@ -54,12 +53,15 @@ pg_old_snapshot_time_mapping(PG_FUNCTION_ARGS)
 	if (SRF_IS_FIRSTCALL())
 	{
 		MemoryContext oldcontext;
+		TupleDesc	tupdesc;
 
 		funcctx = SRF_FIRSTCALL_INIT();
 		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
 		mapping = GetOldSnapshotTimeMapping();
 		funcctx->user_fctx = mapping;
-		funcctx->tuple_desc = MakeOldSnapshotTimeMappingTupleDesc();
+		if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+			elog(ERROR, "return type must be a row type");
+		funcctx->tuple_desc = tupdesc;
 		MemoryContextSwitchTo(oldcontext);
 	}
 
@@ -101,26 +103,6 @@ GetOldSnapshotTimeMapping(void)
 	return mapping;
 }
 
-/*
- * Build a tuple descriptor for the pg_old_snapshot_time_mapping() SRF.
- */
-static TupleDesc
-MakeOldSnapshotTimeMappingTupleDesc(void)
-{
-	TupleDesc	tupdesc;
-
-	tupdesc = CreateTemplateTupleDesc(NUM_TIME_MAPPING_COLUMNS);
-
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "array_offset",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "end_timestamp",
-					   TIMESTAMPTZOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "newest_xmin",
-					   XIDOID, -1, 0);
-
-	return BlessTupleDesc(tupdesc);
-}
-
 /*
  * Convert one entry from the old snapshot time mapping to a HeapTuple.
  */

contrib/pg_visibility/pg_visibility.c

@@ -291,10 +291,8 @@ pg_visibility_map_summary(PG_FUNCTION_ARGS)
 		ReleaseBuffer(vmbuffer);
 	relation_close(rel, AccessShareLock);
 
-	tupdesc = CreateTemplateTupleDesc(2);
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "all_visible", INT8OID, -1, 0);
+		elog(ERROR, "return type must be a row type");
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "all_frozen", INT8OID, -1, 0);
-	tupdesc = BlessTupleDesc(tupdesc);
 
 	values[0] = Int64GetDatum(all_visible);
 	values[1] = Int64GetDatum(all_frozen);

src/backend/access/transam/commit_ts.c

@@ -422,18 +422,8 @@ pg_last_committed_xact(PG_FUNCTION_ARGS)
 	/* and construct a tuple with our data */
 	xid = GetLatestCommitTsData(&ts, &nodeid);
 
-	/*
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	 * Construct a tuple descriptor for the result row.  This must match this
+		elog(ERROR, "return type must be a row type");
-	 * function's pg_proc entry!
-	 */
-	tupdesc = CreateTemplateTupleDesc(3);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "xid",
-					   XIDOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "timestamp",
-					   TIMESTAMPTZOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "roident",
-					   OIDOID, -1, 0);
-	tupdesc = BlessTupleDesc(tupdesc);
 
 	if (!TransactionIdIsNormal(xid))
 	{
@@ -476,16 +466,8 @@ pg_xact_commit_timestamp_origin(PG_FUNCTION_ARGS)
 
 	found = TransactionIdGetCommitTsData(xid, &ts, &nodeid);
 
-	/*
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	 * Construct a tuple descriptor for the result row.  This must match this
+		elog(ERROR, "return type must be a row type");
-	 * function's pg_proc entry!
-	 */
-	tupdesc = CreateTemplateTupleDesc(2);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "timestamp",
-					   TIMESTAMPTZOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "roident",
-					   OIDOID, -1, 0);
-	tupdesc = BlessTupleDesc(tupdesc);
 
 	if (!found)
 	{

src/backend/access/transam/multixact.c

@@ -3373,12 +3373,9 @@ pg_get_multixact_members(PG_FUNCTION_ARGS)
 												false);
 		multi->iter = 0;
 
-		tupdesc = CreateTemplateTupleDesc(2);
+		if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "xid",
+			elog(ERROR, "return type must be a row type");
-						   XIDOID, -1, 0);
+		funccxt->tuple_desc = tupdesc;
-		TupleDescInitEntry(tupdesc, (AttrNumber) 2, "mode",
-						   TEXTOID, -1, 0);
-
 		funccxt->attinmeta = TupleDescGetAttInMetadata(tupdesc);
 		funccxt->user_fctx = multi;
 

src/backend/catalog/objectaddress.c

@@ -2397,14 +2397,8 @@ pg_get_object_address(PG_FUNCTION_ARGS)
 	if (relation)
 		relation_close(relation, AccessShareLock);
 
-	tupdesc = CreateTemplateTupleDesc(3);
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "classid",
+		elog(ERROR, "return type must be a row type");
-					   OIDOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "objid",
-					   OIDOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "objsubid",
-					   INT4OID, -1, 0);
-	tupdesc = BlessTupleDesc(tupdesc);
 
 	values[0] = ObjectIdGetDatum(addr.classId);
 	values[1] = ObjectIdGetDatum(addr.objectId);
@@ -4244,21 +4238,8 @@ pg_identify_object(PG_FUNCTION_ARGS)
 	address.objectId = objid;
 	address.objectSubId = objsubid;
 
-	/*
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	 * Construct a tuple descriptor for the result row.  This must match this
+		elog(ERROR, "return type must be a row type");
-	 * function's pg_proc entry!
-	 */
-	tupdesc = CreateTemplateTupleDesc(4);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "type",
-					   TEXTOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "schema",
-					   TEXTOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "name",
-					   TEXTOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "identity",
-					   TEXTOID, -1, 0);
-
-	tupdesc = BlessTupleDesc(tupdesc);
 
 	if (is_objectclass_supported(address.classId))
 	{
@@ -4374,19 +4355,8 @@ pg_identify_object_as_address(PG_FUNCTION_ARGS)
 	address.objectId = objid;
 	address.objectSubId = objsubid;
 
-	/*
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	 * Construct a tuple descriptor for the result row.  This must match this
+		elog(ERROR, "return type must be a row type");
-	 * function's pg_proc entry!
-	 */
-	tupdesc = CreateTemplateTupleDesc(3);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "type",
-					   TEXTOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "object_names",
-					   TEXTARRAYOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "object_args",
-					   TEXTARRAYOID, -1, 0);
-
-	tupdesc = BlessTupleDesc(tupdesc);
 
 	/* object type, which can never be NULL */
 	values[0] = CStringGetTextDatum(getObjectTypeDescription(&address, true));

src/backend/commands/sequence.c

@@ -1762,23 +1762,8 @@ pg_sequence_parameters(PG_FUNCTION_ARGS)
 				 errmsg("permission denied for sequence %s",
 						get_rel_name(relid))));
 
-	tupdesc = CreateTemplateTupleDesc(7);
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "start_value",
+		elog(ERROR, "return type must be a row type");
-					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "minimum_value",
-					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "maximum_value",
-					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "increment",
-					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "cycle_option",
-					   BOOLOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "cache_size",
-					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "data_type",
-					   OIDOID, -1, 0);
-
-	BlessTupleDesc(tupdesc);
 
 	memset(isnull, 0, sizeof(isnull));
 

src/backend/tsearch/wparser.c

@@ -46,7 +46,8 @@ typedef struct HeadlineJsonState
 static text *headline_json_value(void *_state, char *elem_value, int elem_len);
 
 static void
-tt_setup_firstcall(FuncCallContext *funcctx, Oid prsid)
+tt_setup_firstcall(FuncCallContext *funcctx, FunctionCallInfo fcinfo,
+				   Oid prsid)
 {
 	TupleDesc	tupdesc;
 	MemoryContext oldcontext;
@@ -66,15 +67,11 @@ tt_setup_firstcall(FuncCallContext *funcctx, Oid prsid)
 															 (Datum) 0));
 	funcctx->user_fctx = (void *) st;
 
-	tupdesc = CreateTemplateTupleDesc(3);
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "tokid",
+		elog(ERROR, "return type must be a row type");
-					   INT4OID, -1, 0);
+	funcctx->tuple_desc = tupdesc;
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "alias",
-					   TEXTOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "description",
-					   TEXTOID, -1, 0);
-
 	funcctx->attinmeta = TupleDescGetAttInMetadata(tupdesc);
+
 	MemoryContextSwitchTo(oldcontext);
 }
 
@@ -116,7 +113,7 @@ ts_token_type_byid(PG_FUNCTION_ARGS)
 	if (SRF_IS_FIRSTCALL())
 	{
 		funcctx = SRF_FIRSTCALL_INIT();
-		tt_setup_firstcall(funcctx, PG_GETARG_OID(0));
+		tt_setup_firstcall(funcctx, fcinfo, PG_GETARG_OID(0));
 	}
 
 	funcctx = SRF_PERCALL_SETUP();
@@ -139,7 +136,7 @@ ts_token_type_byname(PG_FUNCTION_ARGS)
 
 		funcctx = SRF_FIRSTCALL_INIT();
 		prsId = get_ts_parser_oid(textToQualifiedNameList(prsname), false);
-		tt_setup_firstcall(funcctx, prsId);
+		tt_setup_firstcall(funcctx, fcinfo, prsId);
 	}
 
 	funcctx = SRF_PERCALL_SETUP();
@@ -164,7 +161,8 @@ typedef struct
 
 
 static void
-prs_setup_firstcall(FuncCallContext *funcctx, Oid prsid, text *txt)
+prs_setup_firstcall(FuncCallContext *funcctx, FunctionCallInfo fcinfo,
+					Oid prsid, text *txt)
 {
 	TupleDesc	tupdesc;
 	MemoryContext oldcontext;
@@ -209,12 +207,9 @@ prs_setup_firstcall(FuncCallContext *funcctx, Oid prsid, text *txt)
 	st->cur = 0;
 
 	funcctx->user_fctx = (void *) st;
-	tupdesc = CreateTemplateTupleDesc(2);
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "tokid",
+		elog(ERROR, "return type must be a row type");
-					   INT4OID, -1, 0);
+	funcctx->tuple_desc = tupdesc;
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "token",
-					   TEXTOID, -1, 0);
-
 	funcctx->attinmeta = TupleDescGetAttInMetadata(tupdesc);
 	MemoryContextSwitchTo(oldcontext);
 }
@@ -256,7 +251,7 @@ ts_parse_byid(PG_FUNCTION_ARGS)
 		text	   *txt = PG_GETARG_TEXT_PP(1);
 
 		funcctx = SRF_FIRSTCALL_INIT();
-		prs_setup_firstcall(funcctx, PG_GETARG_OID(0), txt);
+		prs_setup_firstcall(funcctx, fcinfo, PG_GETARG_OID(0), txt);
 		PG_FREE_IF_COPY(txt, 1);
 	}
 
@@ -281,7 +276,7 @@ ts_parse_byname(PG_FUNCTION_ARGS)
 
 		funcctx = SRF_FIRSTCALL_INIT();
 		prsId = get_ts_parser_oid(textToQualifiedNameList(prsname), false);
-		prs_setup_firstcall(funcctx, prsId, txt);
+		prs_setup_firstcall(funcctx, fcinfo, prsId, txt);
 	}
 
 	funcctx = SRF_PERCALL_SETUP();

src/backend/utils/adt/datetime.c

@@ -4983,19 +4983,10 @@ pg_timezone_abbrevs(PG_FUNCTION_ARGS)
 		*pindex = 0;
 		funcctx->user_fctx = (void *) pindex;
 
-		/*
+		if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-		 * build tupdesc for result tuples. This must match this function's
+			elog(ERROR, "return type must be a row type");
-		 * pg_proc entry!
+		funcctx->tuple_desc = tupdesc;
-		 */
-		tupdesc = CreateTemplateTupleDesc(3);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "abbrev",
-						   TEXTOID, -1, 0);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 2, "utc_offset",
-						   INTERVALOID, -1, 0);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 3, "is_dst",
-						   BOOLOID, -1, 0);
 
-		funcctx->tuple_desc = BlessTupleDesc(tupdesc);
 		MemoryContextSwitchTo(oldcontext);
 	}
 

src/backend/utils/adt/misc.c

@@ -427,18 +427,9 @@ pg_get_keywords(PG_FUNCTION_ARGS)
 		funcctx = SRF_FIRSTCALL_INIT();
 		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
 
-		tupdesc = CreateTemplateTupleDesc(5);
+		if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "word",
+			elog(ERROR, "return type must be a row type");
-						   TEXTOID, -1, 0);
+		funcctx->tuple_desc = tupdesc;
-		TupleDescInitEntry(tupdesc, (AttrNumber) 2, "catcode",
-						   CHAROID, -1, 0);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 3, "barelabel",
-						   BOOLOID, -1, 0);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 4, "catdesc",
-						   TEXTOID, -1, 0);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 5, "baredesc",
-						   TEXTOID, -1, 0);
-
 		funcctx->attinmeta = TupleDescGetAttInMetadata(tupdesc);
 
 		MemoryContextSwitchTo(oldcontext);
@@ -515,20 +506,8 @@ pg_get_catalog_foreign_keys(PG_FUNCTION_ARGS)
 		funcctx = SRF_FIRSTCALL_INIT();
 		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
 
-		tupdesc = CreateTemplateTupleDesc(6);
+		if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "fktable",
+			elog(ERROR, "return type must be a row type");
-						   REGCLASSOID, -1, 0);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 2, "fkcols",
-						   TEXTARRAYOID, -1, 0);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 3, "pktable",
-						   REGCLASSOID, -1, 0);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 4, "pkcols",
-						   TEXTARRAYOID, -1, 0);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 5, "is_array",
-						   BOOLOID, -1, 0);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 6, "is_opt",
-						   BOOLOID, -1, 0);
-
 		funcctx->tuple_desc = BlessTupleDesc(tupdesc);
 
 		/*

src/backend/utils/adt/partitionfuncs.c

@@ -88,17 +88,9 @@ pg_partition_tree(PG_FUNCTION_ARGS)
 		 */
 		partitions = find_all_inheritors(rootrelid, AccessShareLock, NULL);
 
-		tupdesc = CreateTemplateTupleDesc(PG_PARTITION_TREE_COLS);
+		if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "relid",
+			elog(ERROR, "return type must be a row type");
-						   REGCLASSOID, -1, 0);
+		funcctx->tuple_desc = tupdesc;
-		TupleDescInitEntry(tupdesc, (AttrNumber) 2, "parentid",
-						   REGCLASSOID, -1, 0);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 3, "isleaf",
-						   BOOLOID, -1, 0);
-		TupleDescInitEntry(tupdesc, (AttrNumber) 4, "level",
-						   INT4OID, -1, 0);
-
-		funcctx->tuple_desc = BlessTupleDesc(tupdesc);
 
 		/* The only state we need is the partition list */
 		funcctx->user_fctx = (void *) partitions;

src/backend/utils/adt/tsvector_op.c

@@ -647,7 +647,9 @@ tsvector_unnest(PG_FUNCTION_ARGS)
 						   INT2ARRAYOID, -1, 0);
 		TupleDescInitEntry(tupdesc, (AttrNumber) 3, "weights",
 						   TEXTARRAYOID, -1, 0);
-		funcctx->tuple_desc = BlessTupleDesc(tupdesc);
+		if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+			elog(ERROR, "return type must be a row type");
+		funcctx->tuple_desc = tupdesc;
 
 		funcctx->user_fctx = PG_GETARG_TSVECTOR_COPY(0);
 
@@ -2302,14 +2304,9 @@ ts_setup_firstcall(FunctionCallInfo fcinfo, FuncCallContext *funcctx,
 		}
 	Assert(stat->stackpos <= stat->maxdepth);
 
-	tupdesc = CreateTemplateTupleDesc(3);
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "word",
+		elog(ERROR, "return type must be a row type");
-					   TEXTOID, -1, 0);
+	funcctx->tuple_desc = tupdesc;
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "ndoc",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "nentry",
-					   INT4OID, -1, 0);
-	funcctx->tuple_desc = BlessTupleDesc(tupdesc);
 	funcctx->attinmeta = TupleDescGetAttInMetadata(tupdesc);
 
 	MemoryContextSwitchTo(oldcontext);

src/backend/utils/misc/pg_controldata.c

@@ -38,20 +38,8 @@ pg_control_system(PG_FUNCTION_ARGS)
 	ControlFileData *ControlFile;
 	bool		crc_ok;
 
-	/*
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	 * Construct a tuple descriptor for the result row.  This must match this
+		elog(ERROR, "return type must be a row type");
-	 * function's pg_proc entry!
-	 */
-	tupdesc = CreateTemplateTupleDesc(4);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "pg_control_version",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "catalog_version_no",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "system_identifier",
-					   INT8OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "pg_control_last_modified",
-					   TIMESTAMPTZOID, -1, 0);
-	tupdesc = BlessTupleDesc(tupdesc);
 
 	/* read the control file */
 	ControlFile = get_controlfile(DataDir, &crc_ok);
@@ -88,48 +76,8 @@ pg_control_checkpoint(PG_FUNCTION_ARGS)
 	char		xlogfilename[MAXFNAMELEN];
 	bool		crc_ok;
 
-	/*
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	 * Construct a tuple descriptor for the result row.  This must match this
+		elog(ERROR, "return type must be a row type");
-	 * function's pg_proc entry!
-	 */
-	tupdesc = CreateTemplateTupleDesc(18);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "checkpoint_lsn",
-					   PG_LSNOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "redo_lsn",
-					   PG_LSNOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "redo_wal_file",
-					   TEXTOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "timeline_id",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "prev_timeline_id",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "full_page_writes",
-					   BOOLOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "next_xid",
-					   TEXTOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "next_oid",
-					   OIDOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 9, "next_multixact_id",
-					   XIDOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 10, "next_multi_offset",
-					   XIDOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 11, "oldest_xid",
-					   XIDOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 12, "oldest_xid_dbid",
-					   OIDOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 13, "oldest_active_xid",
-					   XIDOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 14, "oldest_multi_xid",
-					   XIDOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 15, "oldest_multi_dbid",
-					   OIDOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 16, "oldest_commit_ts_xid",
-					   XIDOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 17, "newest_commit_ts_xid",
-					   XIDOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 18, "checkpoint_time",
-					   TIMESTAMPTZOID, -1, 0);
-	tupdesc = BlessTupleDesc(tupdesc);
 
 	/* Read the control file. */
 	ControlFile = get_controlfile(DataDir, &crc_ok);
@@ -217,22 +165,8 @@ pg_control_recovery(PG_FUNCTION_ARGS)
 	ControlFileData *ControlFile;
 	bool		crc_ok;
 
-	/*
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	 * Construct a tuple descriptor for the result row.  This must match this
+		elog(ERROR, "return type must be a row type");
-	 * function's pg_proc entry!
-	 */
-	tupdesc = CreateTemplateTupleDesc(5);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "min_recovery_end_lsn",
-					   PG_LSNOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "min_recovery_end_timeline",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "backup_start_lsn",
-					   PG_LSNOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "backup_end_lsn",
-					   PG_LSNOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "end_of_backup_record_required",
-					   BOOLOID, -1, 0);
-	tupdesc = BlessTupleDesc(tupdesc);
 
 	/* read the control file */
 	ControlFile = get_controlfile(DataDir, &crc_ok);
@@ -270,34 +204,8 @@ pg_control_init(PG_FUNCTION_ARGS)
 	ControlFileData *ControlFile;
 	bool		crc_ok;
 
-	/*
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-	 * Construct a tuple descriptor for the result row.  This must match this
+		elog(ERROR, "return type must be a row type");
-	 * function's pg_proc entry!
-	 */
-	tupdesc = CreateTemplateTupleDesc(11);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "max_data_alignment",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "database_block_size",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "blocks_per_segment",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "wal_block_size",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "bytes_per_wal_segment",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "max_identifier_length",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "max_index_columns",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "max_toast_chunk_size",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 9, "large_object_chunk_size",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 10, "float8_pass_by_value",
-					   BOOLOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 11, "data_page_checksum_version",
-					   INT4OID, -1, 0);
-	tupdesc = BlessTupleDesc(tupdesc);
 
 	/* read the control file */
 	ControlFile = get_controlfile(DataDir, &crc_ok);