Fix catalog data of pg_stop_backup(), labelled v2

This function has been incorrectly marked as a set-returning function
with prorows (estimated number of rows) set to 1 since its creation in
7117685, that introduced non-exclusive backups.  There is no need for
that as the function is designed to return only one tuple.

This commit fixes the catalog definition of pg_stop_backup_v2() so as it
is not marked as proretset anymore, with prorows set to 0.  This
simplifies its internals by removing one tuplestore (used for one single
record anyway) and by removing all the checks related to a set-returning
function.

Issue found during my quest to simplify some of the logic used in
in-core system functions.

Bump catalog version.

Reviewed-by: Aleksander Alekseev, Kyotaro Horiguchi
Discussion: https://postgr.es/m/Yh8guT78f1Ercfzw@paquier.xyz

Author: michaelpq

src/backend/access/transam/xlogfuncs.c

@@ -165,43 +165,20 @@ pg_stop_backup(PG_FUNCTION_ARGS)
 Datum
 pg_stop_backup_v2(PG_FUNCTION_ARGS)
 {
-	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+#define PG_STOP_BACKUP_V2_COLS 3
 	TupleDesc	tupdesc;
-	Tuplestorestate *tupstore;
-	MemoryContext per_query_ctx;
-	MemoryContext oldcontext;
-	Datum		values[3];
-	bool		nulls[3];
+	Datum		values[PG_STOP_BACKUP_V2_COLS];
+	bool		nulls[PG_STOP_BACKUP_V2_COLS];
 
 	bool		exclusive = PG_GETARG_BOOL(0);
 	bool		waitforarchive = PG_GETARG_BOOL(1);
 	XLogRecPtr	stoppoint;
 	SessionBackupState status = get_backup_status();
 
-	/* 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")));
-
-	/* Build a tuple descriptor for our result type */
+	/* Initialize attributes information in the tuple descriptor */
 	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
 		elog(ERROR, "return type must be a row type");
 
-	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
-	oldcontext = MemoryContextSwitchTo(per_query_ctx);
-
-	tupstore = tuplestore_begin_heap(true, false, work_mem);
-	rsinfo->returnMode = SFRM_Materialize;
-	rsinfo->setResult = tupstore;
-	rsinfo->setDesc = tupdesc;
-
-	MemoryContextSwitchTo(oldcontext);
-
 	MemSet(values, 0, sizeof(values));
 	MemSet(nulls, 0, sizeof(nulls));
 
@@ -251,9 +228,8 @@ pg_stop_backup_v2(PG_FUNCTION_ARGS)
 	/* Stoppoint is included on both exclusive and nonexclusive backups */
 	values[0] = LSNGetDatum(stoppoint);
 
-	tuplestore_putvalues(tupstore, tupdesc, values, nulls);
-
-	return (Datum) 0;
+	/* Returns the record as Datum */
+	PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
 }
 
 /*

src/backend/catalog/system_functions.sql

@@ -384,7 +384,7 @@ CREATE OR REPLACE FUNCTION
 CREATE OR REPLACE FUNCTION pg_stop_backup (
         exclusive boolean, wait_for_archive boolean DEFAULT true,
         OUT lsn pg_lsn, OUT labelfile text, OUT spcmapfile text)
-  RETURNS SETOF record STRICT VOLATILE LANGUAGE internal as 'pg_stop_backup_v2'
+  RETURNS record STRICT VOLATILE LANGUAGE internal as 'pg_stop_backup_v2'
   PARALLEL RESTRICTED;
 
 CREATE OR REPLACE FUNCTION

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202203011
+#define CATALOG_VERSION_NO	202203031
 
 #endif

src/include/catalog/pg_proc.dat

@@ -6275,9 +6275,9 @@
   proname => 'pg_stop_backup', provolatile => 'v', proparallel => 'r',
   prorettype => 'pg_lsn', proargtypes => '', prosrc => 'pg_stop_backup' },
 { oid => '2739', descr => 'finish taking an online backup',
-  proname => 'pg_stop_backup', prorows => '1', proretset => 't',
-  provolatile => 'v', proparallel => 'r', prorettype => 'record',
-  proargtypes => 'bool bool', proallargtypes => '{bool,bool,pg_lsn,text,text}',
+  proname => 'pg_stop_backup', provolatile => 'v', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'bool bool',
+  proallargtypes => '{bool,bool,pg_lsn,text,text}',
   proargmodes => '{i,i,o,o,o}',
   proargnames => '{exclusive,wait_for_archive,lsn,labelfile,spcmapfile}',
   prosrc => 'pg_stop_backup_v2' },