From d5768dce10576c2fb1254c03fb29475d4fac6bb4 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 8 Feb 2010 20:39:52 +0000
Subject: Create an official API function for C functions to use to check if
 they are being called as aggregates, and to get the aggregate transition
 state memory context if needed.  Use it instead of poking directly into
 AggState and WindowAggState in places that shouldn't know so much.

We should have done this in 8.4, probably, but better late than never.

Revised version of a patch by Hitoshi Harada.
---
 src/backend/utils/adt/varlena.c | 40 ++++++++++++++++++----------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

(limited to 'src/backend/utils/adt/varlena.c')

diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index 096ca75bf93..652e1e6add4 100644
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/varlena.c,v 1.175 2010/02/01 03:14:43 itagaki Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/varlena.c,v 1.176 2010/02/08 20:39:51 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,7 +21,6 @@
 #include "libpq/md5.h"
 #include "libpq/pqformat.h"
 #include "miscadmin.h"
-#include "nodes/execnodes.h"
 #include "parser/scansup.h"
 #include "regex/regex.h"
 #include "utils/builtins.h"
@@ -74,7 +73,7 @@ static bytea *bytea_substring(Datum str,
 				int L,
 				bool length_not_specified);
 static bytea *bytea_overlay(bytea *t1, bytea *t2, int sp, int sl);
-static StringInfo makeStringAggState(fmNodePtr context);
+static StringInfo makeStringAggState(FunctionCallInfo fcinfo);
 
 
 /*****************************************************************************
@@ -3327,25 +3326,25 @@ pg_column_size(PG_FUNCTION_ARGS)
  * actually used at all, and on subsequent calls the delimiter precedes
  * the associated value.
  */
+
+/* subroutine to initialize state */
 static StringInfo
-makeStringAggState(fmNodePtr context)
+makeStringAggState(FunctionCallInfo fcinfo)
 {
 	StringInfo		state;
 	MemoryContext	aggcontext;
 	MemoryContext	oldcontext;
 
-	if (context && IsA(context, AggState))
-		aggcontext = ((AggState *) context)->aggcontext;
-	else if (context && IsA(context, WindowAggState))
-		aggcontext = ((WindowAggState *) context)->wincontext;
-	else
+	if (!AggCheckCallContext(fcinfo, &aggcontext))
 	{
 		/* cannot be called directly because of internal-type argument */
 		elog(ERROR, "string_agg_transfn called in non-aggregate context");
-		aggcontext = NULL;		/* keep compiler quiet */
 	}
 
-	/* Create state in aggregate context */
+	/*
+	 * Create state in aggregate context.  It'll stay there across subsequent
+	 * calls.
+	 */
 	oldcontext = MemoryContextSwitchTo(aggcontext);
 	state = makeStringInfo();
 	MemoryContextSwitchTo(oldcontext);
@@ -3360,11 +3359,11 @@ string_agg_transfn(PG_FUNCTION_ARGS)
 
 	state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);
 
-	/* Append the element unless not null. */
+	/* Append the element unless null. */
 	if (!PG_ARGISNULL(1))
 	{
 		if (state == NULL)
-			state = makeStringAggState(fcinfo->context);
+			state = makeStringAggState(fcinfo);
 		appendStringInfoText(state, PG_GETARG_TEXT_PP(1));	/* value */
 	}
 
@@ -3382,11 +3381,12 @@ string_agg_delim_transfn(PG_FUNCTION_ARGS)
 
 	state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);
 
-	/* Append the value unless not null. */
+	/* Append the value unless null. */
 	if (!PG_ARGISNULL(1))
 	{
+		/* On the first time through, we ignore the delimiter. */
 		if (state == NULL)
-			state = makeStringAggState(fcinfo->context);
+			state = makeStringAggState(fcinfo);
 		else if (!PG_ARGISNULL(2))
 			appendStringInfoText(state, PG_GETARG_TEXT_PP(2));	/* delimiter */
 
@@ -3405,15 +3405,11 @@ string_agg_finalfn(PG_FUNCTION_ARGS)
 {
 	StringInfo		state;
 
-	if (PG_ARGISNULL(0))
-		PG_RETURN_NULL();
-
 	/* cannot be called directly because of internal-type argument */
-	Assert(fcinfo->context &&
-		   (IsA(fcinfo->context, AggState) ||
-			IsA(fcinfo->context, WindowAggState)));
+	Assert(AggCheckCallContext(fcinfo, NULL));
+
+	state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);
 
-	state = (StringInfo) PG_GETARG_POINTER(0);
 	if (state != NULL)
 		PG_RETURN_TEXT_P(cstring_to_text(state->data));
 	else
-- 
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