Create routine able to set single-call SRFs for Materialize mode

Set-returning functions that use the Materialize mode, creating a
tuplestore to include all the tuples returned in a set rather than doing
so in multiple calls, use roughly the same set of steps to prepare
ReturnSetInfo for this job:
- Check if ReturnSetInfo supports returning a tuplestore and if the
materialize mode is enabled.
- Create a tuplestore for all the tuples part of the returned set in the
per-query memory context, stored in ReturnSetInfo->setResult.
- Build a tuple descriptor mostly from get_call_result_type(), then
stored in ReturnSetInfo->setDesc.  Note that there are some cases where
the SRF's tuple descriptor has to be the one specified by the function
caller.

This refactoring is done so as there are (well, should be) no behavior
changes in any of the in-core functions refactored, and the centralized
function that checks and sets up the function's ReturnSetInfo can be
controlled with a set of bits32 options.  Two of them prove to be
necessary now:
- SRF_SINGLE_USE_EXPECTED to use expectedDesc as tuple descriptor, as
expected by the function's caller.
- SRF_SINGLE_BLESS to validate the tuple descriptor for the SRF.

The same initialization pattern is simplified in 28 places per my
count as of src/backend/, shaving up to ~900 lines of code.  These
mostly come from the removal of the per-query initializations and the
sanity checks now grouped in a single location.  There are more
locations that could be simplified in contrib/, that are left for a
follow-up cleanup.

fcc2817, 07daca5 and d61a361 have prepared the areas of the code related
to this change, to ease this refactoring.

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

5 files changed, 15 insertions, 131 deletions

diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
index 5a68d6deadc..6f25b2c2ad5 100644
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -930,34 +930,8 @@ pg_stat_get_subscription(PG_FUNCTION_ARGS)
 	Oid			subid = PG_ARGISNULL(0) ? InvalidOid : PG_GETARG_OID(0);
 	int			i;
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
-	TupleDesc	tupdesc;
-	Tuplestorestate *tupstore;
-	MemoryContext per_query_ctx;
-	MemoryContext oldcontext;
 
-	/* 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 */
-	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);
+	SetSingleFuncCall(fcinfo, 0);
 
 	/* Make sure we get consistent view of the workers. */
 	LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
@@ -1010,7 +984,8 @@ pg_stat_get_subscription(PG_FUNCTION_ARGS)
 		else
 			values[7] = TimestampTzGetDatum(worker.reply_time);
 
-		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
+							 values, nulls);
 
 		/*
 		 * If only a single subscription was requested, and we found it,
diff --git a/src/backend/replication/logical/logicalfuncs.c b/src/backend/replication/logical/logicalfuncs.c
index 3bd770a3ba6..6058d36e0d5 100644
--- a/src/backend/replication/logical/logicalfuncs.c
+++ b/src/backend/replication/logical/logicalfuncs.c
@@ -142,25 +142,11 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin
 				 errmsg("options array must not be null")));
 	arr = PG_GETARG_ARRAYTYPE_P(3);
 
-	/* 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")));
-
 	/* state to write output to */
 	p = palloc0(sizeof(DecodingOutputState));
 
 	p->binary_output = binary;
 
-	/* Build a tuple descriptor for our result type */
-	if (get_call_result_type(fcinfo, NULL, &p->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);
 
@@ -203,10 +189,9 @@ pg_logical_slot_get_changes_guts(FunctionCallInfo fcinfo, bool confirm, bool bin
 		}
 	}
 
-	p->tupstore = tuplestore_begin_heap(true, false, work_mem);
-	rsinfo->returnMode = SFRM_Materialize;
-	rsinfo->setResult = p->tupstore;
-	rsinfo->setDesc = p->tupdesc;
+	SetSingleFuncCall(fcinfo, 0);
+	p->tupstore = rsinfo->setResult;
+	p->tupdesc = rsinfo->setDesc;
 
 	/*
 	 * Compute the current end-of-wal.
diff --git a/src/backend/replication/logical/origin.c b/src/backend/replication/logical/origin.c
index 76055a8a036..0e38eff0f00 100644
--- a/src/backend/replication/logical/origin.c
+++ b/src/backend/replication/logical/origin.c
@@ -1482,40 +1482,13 @@ Datum
 pg_show_replication_origin_status(PG_FUNCTION_ARGS)
 {
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
-	TupleDesc	tupdesc;
-	Tuplestorestate *tupstore;
-	MemoryContext per_query_ctx;
-	MemoryContext oldcontext;
 	int			i;
 #define REPLICATION_ORIGIN_PROGRESS_COLS 4
 
 	/* we want to return 0 rows if slot is set to zero */
 	replorigin_check_prerequisites(false, true);
 
-	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")));
-	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-		elog(ERROR, "return type must be a row type");
-
-	if (tupdesc->natts != REPLICATION_ORIGIN_PROGRESS_COLS)
-		elog(ERROR, "wrong function definition");
-
-	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);
-
+	SetSingleFuncCall(fcinfo, 0);
 
 	/* prevent slots from being concurrently dropped */
 	LWLockAcquire(ReplicationOriginLock, LW_SHARED);
@@ -1565,7 +1538,8 @@ pg_show_replication_origin_status(PG_FUNCTION_ARGS)
 
 		LWLockRelease(&state->lock);
 
-		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
+							 values, nulls);
 	}
 
 	LWLockRelease(ReplicationOriginLock);
diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index 886899afd22..ca945994ef0 100644
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -233,42 +233,16 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
 {
 #define PG_GET_REPLICATION_SLOTS_COLS 14
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
-	TupleDesc	tupdesc;
-	Tuplestorestate *tupstore;
-	MemoryContext per_query_ctx;
-	MemoryContext oldcontext;
 	XLogRecPtr	currlsn;
 	int			slotno;
 
-	/* 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 */
-	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-		elog(ERROR, "return type must be a row type");
-
 	/*
 	 * We don't require any special permission to see this function's data
 	 * because nothing should be sensitive. The most critical being the slot
 	 * name, which shouldn't contain anything particularly sensitive.
 	 */
 
-	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);
+	SetSingleFuncCall(fcinfo, 0);
 
 	currlsn = GetXLogWriteRecPtr();
 
@@ -431,7 +405,8 @@ pg_get_replication_slots(PG_FUNCTION_ARGS)
 
 		Assert(i == PG_GET_REPLICATION_SLOTS_COLS);
 
-		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
+							 values, nulls);
 	}
 
 	LWLockRelease(ReplicationSlotControlLock);
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 5a718b1fe9b..2d0292a092e 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -3403,37 +3403,11 @@ pg_stat_get_wal_senders(PG_FUNCTION_ARGS)
 {
 #define PG_STAT_GET_WAL_SENDERS_COLS	12
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
-	TupleDesc	tupdesc;
-	Tuplestorestate *tupstore;
-	MemoryContext per_query_ctx;
-	MemoryContext oldcontext;
 	SyncRepStandbyData *sync_standbys;
 	int			num_standbys;
 	int			i;
 
-	/* 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 */
-	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);
+	SetSingleFuncCall(fcinfo, 0);
 
 	/*
 	 * Get the currently active synchronous standbys.  This could be out of
@@ -3577,7 +3551,8 @@ pg_stat_get_wal_senders(PG_FUNCTION_ARGS)
 				values[11] = TimestampTzGetDatum(replyTime);
 		}
 
-		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
+							 values, nulls);
 	}
 
 	return (Datum) 0;