Clean up and simplify code in a couple of set-returning functions

The following set-returning functions have their logic simplified, to be
more consistent with other in-core areas:
- pg_prepared_statement()'s tuple descriptor is now created with
get_call_result_type() instead of being created from scratch, saving
from some duplication with pg_proc.dat.
- show_all_file_settings(), similarly, now uses get_call_result_type()
to build its tuple descriptor instead of creating it from scratch.
- pg_options_to_table() made use of a static routine called only once.
This commit removes this internal routine to make the function easier to
follow.
- pg_config() was using a unique logic style, doing checks on the tuple
descriptor passed down in expectedDesc, but it has no need to do so.
This switches the function to use a tuplestore with a tuple descriptor
retrieved from get_call_result_type(), instead.

This simplifies an upcoming patch aimed at refactoring the way
tuplestores are created and checked in set-returning functions, this
change making sense as its own independent cleanup by shaving some
code.

Author: Melanie Plageman, Michael Paquier
Reviewed-by: Justin Pryzby
Discussion: https://postgr.es/m/CAAKRu_azyd1Z3W_r7Ou4sorTjRCs+PxeHw1CWJeXKofkE6TuZg@mail.gmail.com

1 files changed, 3 insertions, 17 deletions

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index bf7ec0d4666..1e3650184b1 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -10174,6 +10174,9 @@ show_all_file_settings(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("materialize mode required, but it is not allowed in this context")));
 
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
 	/* Scan the config files using current context as workspace */
 	conf = ProcessConfigFileInternal(PGC_SIGHUP, false, DEBUG3);
 
@@ -10181,23 +10184,6 @@ show_all_file_settings(PG_FUNCTION_ARGS)
 	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
 	oldcontext = MemoryContextSwitchTo(per_query_ctx);
 
-	/* Build a tuple descriptor for our result type */
-	tupdesc = CreateTemplateTupleDesc(NUM_PG_FILE_SETTINGS_ATTS);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "sourcefile",
-					   TEXTOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "sourceline",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "seqno",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "name",
-					   TEXTOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "setting",
-					   TEXTOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "applied",
-					   BOOLOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "error",
-					   TEXTOID, -1, 0);
-
 	/* Build a tuplestore to return our results in */
 	tupstore = tuplestore_begin_heap(true, false, work_mem);
 	rsinfo->returnMode = SFRM_Materialize;