Simplify SRFs using materialize mode in contrib/ modules

9e98583 introduced a helper to centralize building their needed state
(tuplestore, tuple descriptors, etc.), checking for any errors.  This
commit updates all places of contrib/ that can be switched to use
SetSingleFuncCall() as a drop-in replacement, resulting in the removal
of a lot of boilerplate code in all the modules updated by this commit.

Per analysis, some places remain as they are:
- pg_logdir_ls() in adminpack/ uses historically TYPEFUNC_RECORD as
return type, and I suspect that changing it may cause issues at run-time
with some of its past versions, down to 1.0.
- dblink/ uses a wrapper function doing exactly the work of
SetSingleFuncCall().  Here the switch should be possible, but rather
invasive so it does not seem the extra backpatch maintenance cost.
- tablefunc/, similarly, uses multiple helper functions with portions of
SetSingleFuncCall() spread across the code paths of this module.

Author: Melanie Plageman
Discussion: https://postgr.es/m/CAAKRu_bvDPJoL9mH6eYwvBpPtTGQwbDzfJbCM-OjkSZDu5yTPg@mail.gmail.com

1 files changed, 3 insertions, 30 deletions

diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index d803253ceaf..9e525a6ad3b 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -1494,10 +1494,6 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
 							bool showtext)
 {
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
-	TupleDesc	tupdesc;
-	Tuplestorestate *tupstore;
-	MemoryContext per_query_ctx;
-	MemoryContext oldcontext;
 	Oid			userid = GetUserId();
 	bool		is_allowed_role = false;
 	char	   *qbuffer = NULL;
@@ -1516,30 +1512,14 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				 errmsg("pg_stat_statements must be loaded via shared_preload_libraries")));
 
-	/* 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")));
-
-	/* Switch into long-lived context to construct returned data structures */
-	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
-	oldcontext = MemoryContextSwitchTo(per_query_ctx);
-
-	/* Build a tuple descriptor for our result type */
-	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-		elog(ERROR, "return type must be a row type");
+	SetSingleFuncCall(fcinfo, 0);
 
 	/*
 	 * Check we have the expected number of output arguments.  Aside from
 	 * being a good safety check, we need a kluge here to detect API version
 	 * 1.1, which was wedged into the code in an ill-considered way.
 	 */
-	switch (tupdesc->natts)
+	switch (rsinfo->setDesc->natts)
 	{
 		case PG_STAT_STATEMENTS_COLS_V1_0:
 			if (api_version != PGSS_V1_0)
@@ -1571,13 +1551,6 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
 			elog(ERROR, "incorrect number of output arguments");
 	}
 
-	tupstore = tuplestore_begin_heap(true, false, work_mem);
-	rsinfo->returnMode = SFRM_Materialize;
-	rsinfo->setResult = tupstore;
-	rsinfo->setDesc = tupdesc;
-
-	MemoryContextSwitchTo(oldcontext);
-
 	/*
 	 * We'd like to load the query text file (if needed) while not holding any
 	 * lock on pgss->lock.  In the worst case we'll have to do this again
@@ -1800,7 +1773,7 @@ pg_stat_statements_internal(FunctionCallInfo fcinfo,
 					 api_version == PGSS_V1_9 ? PG_STAT_STATEMENTS_COLS_V1_9 :
 					 -1 /* fail if you forget to update this assert */ ));
 
-		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
 	}
 
 	LWLockRelease(pgss->lock);