Simplify more checks related to set-returning functions

This makes more consistent the SRF-related checks in the area of
PL/pgSQL, PL/Perl, PL/Tcl, pageinspect and some of the JSON worker
functions, making it easier to grep for the same error patterns through
the code, reducing a bit the translation work.

It is worth noting that each_worker_jsonb()/each_worker() in jsonfuncs.c
and pageinspect's brin_page_items() were doing a check on expectedDesc
that is not required as they fetch their tuple descriptor directly from
get_call_result_type().  This looks like a set of copy-paste errors that
have spread over the years.

This commit is a continuation of the changes begun in 07daca5, for any
remaining code paths on sight.  Like fcc2817, this makes the code more
consistent, easing the integration of a larger patch that will refactor
the way tuplestores are created and checked in a good portion of the
set-returning functions present in core.

I have worked my way through the changes of this patch by myself, and
Ranier has proposed the same changes in a different thread in parallel,
though there were some inconsistencies related in expectedDesc in what
was proposed by him.

Author: Michael Paquier, Ranier Vilela
Discussion: https://postgr.es/m/CAAKRu_azyd1Z3W_r7Ou4sorTjRCs+PxeHw1CWJeXKofkE6TuZg@mail.gmail.com
Discussion: https://postgr.es/m/CAEudQApm=AFuJjEHLBjBcJbxcw4pBMwg2sHwXyCXYcbBOj3hpg@mail.gmail.com

contrib/pageinspect/brinfuncs.c

@@ -148,8 +148,7 @@ brin_page_items(PG_FUNCTION_ARGS)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("set-valued function called in context that cannot accept a set")));
-	if (!(rsinfo->allowedModes & SFRM_Materialize) ||
+	if (!(rsinfo->allowedModes & SFRM_Materialize))
-		rsinfo->expectedDesc == NULL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("materialize mode required, but it is not allowed in this context")));

src/backend/utils/adt/jsonfuncs.c

@@ -1927,21 +1927,19 @@ each_worker_jsonb(FunctionCallInfo fcinfo, const char *funcname, bool as_text)
 
 	rsi = (ReturnSetInfo *) fcinfo->resultinfo;
 
-	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
+	if (!rsi || !IsA(rsi, ReturnSetInfo))
-		(rsi->allowedModes & SFRM_Materialize) == 0 ||
-		rsi->expectedDesc == NULL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("set-valued function called in context that "
+				 errmsg("set-valued function called in context that cannot accept a set")));
-						"cannot accept a set")));
+	if (!(rsi->allowedModes & SFRM_Materialize))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not allowed in this context")));
 
 	rsi->returnMode = SFRM_Materialize;
 
 	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
-		ereport(ERROR,
+		elog(ERROR, "return type must be a row type");
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("function returning record called in context "
-						"that cannot accept type record")));
 
 	old_cxt = MemoryContextSwitchTo(rsi->econtext->ecxt_per_query_memory);
 
@@ -2039,13 +2037,15 @@ each_worker(FunctionCallInfo fcinfo, bool as_text)
 
 	rsi = (ReturnSetInfo *) fcinfo->resultinfo;
 
-	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
+	if (!rsi || !IsA(rsi, ReturnSetInfo))
-		(rsi->allowedModes & SFRM_Materialize) == 0 ||
-		rsi->expectedDesc == NULL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("set-valued function called in context that "
+				 errmsg("set-valued function called in context that cannot accept a set")));
-						"cannot accept a set")));
+
+	if (!(rsi->allowedModes & SFRM_Materialize))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not allowed in this context")));
 
 	rsi->returnMode = SFRM_Materialize;
 
@@ -2227,13 +2227,16 @@ elements_worker_jsonb(FunctionCallInfo fcinfo, const char *funcname,
 
 	rsi = (ReturnSetInfo *) fcinfo->resultinfo;
 
-	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
+	if (!rsi || !IsA(rsi, ReturnSetInfo))
-		(rsi->allowedModes & SFRM_Materialize) == 0 ||
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+
+	if (!(rsi->allowedModes & SFRM_Materialize) ||
 		rsi->expectedDesc == NULL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("set-valued function called in context that "
+				 errmsg("materialize mode required, but it is not allowed in this context")));
-						"cannot accept a set")));
 
 	rsi->returnMode = SFRM_Materialize;
 
@@ -2336,13 +2339,16 @@ elements_worker(FunctionCallInfo fcinfo, const char *funcname, bool as_text)
 
 	rsi = (ReturnSetInfo *) fcinfo->resultinfo;
 
-	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
+	if (!rsi || !IsA(rsi, ReturnSetInfo))
-		(rsi->allowedModes & SFRM_Materialize) == 0 ||
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+
+	if (!(rsi->allowedModes & SFRM_Materialize) ||
 		rsi->expectedDesc == NULL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("set-valued function called in context that "
+				 errmsg("materialize mode required, but it is not allowed in this context")));
-						"cannot accept a set")));
 
 	rsi->returnMode = SFRM_Materialize;
 
@@ -3798,12 +3804,15 @@ populate_recordset_worker(FunctionCallInfo fcinfo, const char *funcname,
 
 	rsi = (ReturnSetInfo *) fcinfo->resultinfo;
 
-	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
+	if (!rsi || !IsA(rsi, ReturnSetInfo))
-		(rsi->allowedModes & SFRM_Materialize) == 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("set-valued function called in context that "
+				 errmsg("set-valued function called in context that cannot accept a set")));
-						"cannot accept a set")));
+
+	if (!(rsi->allowedModes & SFRM_Materialize))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not allowed in this context")));
 
 	rsi->returnMode = SFRM_Materialize;
 

src/pl/plperl/plperl.c

@@ -2414,12 +2414,15 @@ plperl_func_handler(PG_FUNCTION_ARGS)
 	if (prodesc->fn_retisset)
 	{
 		/* Check context before allowing the call to go through */
-		if (!rsi || !IsA(rsi, ReturnSetInfo) ||
+		if (!rsi || !IsA(rsi, ReturnSetInfo))
-			(rsi->allowedModes & SFRM_Materialize) == 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-					 errmsg("set-valued function called in context that "
+					 errmsg("set-valued function called in context that cannot accept a set")));
-							"cannot accept a set")));
+
+		if (!(rsi->allowedModes & SFRM_Materialize))
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("materialize mode required, but it is not allowed in this context")));
 	}
 
 	activate_interpreter(prodesc->interp);

src/pl/plpgsql/src/pl_exec.c

@@ -629,11 +629,16 @@ plpgsql_exec_function(PLpgSQL_function *func, FunctionCallInfo fcinfo,
 		ReturnSetInfo *rsi = estate.rsi;
 
 		/* Check caller can handle a set result */
-		if (!rsi || !IsA(rsi, ReturnSetInfo) ||
+		if (!rsi || !IsA(rsi, ReturnSetInfo))
-			(rsi->allowedModes & SFRM_Materialize) == 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 					 errmsg("set-valued function called in context that cannot accept a set")));
+
+		if (!(rsi->allowedModes & SFRM_Materialize))
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("materialize mode required, but it is not allowed in this context")));
+
 		rsi->returnMode = SFRM_Materialize;
 
 		/* If we produced any tuples, send back the result */
@@ -3645,13 +3650,17 @@ exec_init_tuple_store(PLpgSQL_execstate *estate)
 	/*
 	 * Check caller can handle a set result in the way we want
 	 */
-	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
+	if (!rsi || !IsA(rsi, ReturnSetInfo))
-		(rsi->allowedModes & SFRM_Materialize) == 0 ||
-		rsi->expectedDesc == NULL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("set-valued function called in context that cannot accept a set")));
 
+	if (!(rsi->allowedModes & SFRM_Materialize) ||
+		rsi->expectedDesc == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not allowed in this context")));
+
 	/*
 	 * Switch to the right memory context and resource owner for storing the
 	 * tuplestore for return set. If we're within a subtransaction opened for

src/pl/tcl/pltcl.c

@@ -829,12 +829,16 @@ pltcl_func_handler(PG_FUNCTION_ARGS, pltcl_call_state *call_state,
 	{
 		ReturnSetInfo *rsi = (ReturnSetInfo *) fcinfo->resultinfo;
 
-		if (!rsi || !IsA(rsi, ReturnSetInfo) ||
+		if (!rsi || !IsA(rsi, ReturnSetInfo))
-			(rsi->allowedModes & SFRM_Materialize) == 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 					 errmsg("set-valued function called in context that cannot accept a set")));
 
+		if (!(rsi->allowedModes & SFRM_Materialize))
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("materialize mode required, but it is not allowed in this context")));
+
 		call_state->rsi = rsi;
 		call_state->tuple_store_cxt = rsi->econtext->ecxt_per_query_memory;
 		call_state->tuple_store_owner = CurrentResourceOwner;