From 10db3de66eb226e9aed32e789abd532c41f0f471 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 15 Jun 2011 14:05:22 -0400
Subject: [PATCH] Fix failure to account for memory used by
 tuplestore_putvalues().

This oversight could result in a tuplestore using much more than the
intended amount of memory.  It would only happen in a code path that loaded
a tuplestore via tuplestore_putvalues(), and many of those won't emit huge
amounts of data; but cases such as holdable cursors and plpgsql's RETURN
NEXT command could have the problem.  The fix ensures that the tuplestore
will switch to write-to-disk mode when it overruns work_mem.

The potential overrun was finite, because we would still count the space
used by the tuple pointer array, so the tuplestore code would eventually
flip into write-to-disk mode anyway.  When storing wide tuples we would
go far past the expected work_mem usage before that happened; but this
may account for the lack of prior reports.

Back-patch to 8.4, where tuplestore_putvalues was introduced.

Per bug #6061 from Yann Delorme.
---
 src/backend/utils/sort/tuplestore.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/utils/sort/tuplestore.c b/src/backend/utils/sort/tuplestore.c
index b59587b73b3..4d6e3aa0e4b 100644
--- a/src/backend/utils/sort/tuplestore.c
+++ b/src/backend/utils/sort/tuplestore.c
@@ -570,7 +570,8 @@ tuplestore_puttuple(Tuplestorestate *state, HeapTuple tuple)
 	MemoryContext oldcxt = MemoryContextSwitchTo(state->context);
 
 	/*
-	 * Copy the tuple.	(Must do this even in WRITEFILE case.)
+	 * Copy the tuple.  (Must do this even in WRITEFILE case.  Note that
+	 * COPYTUP includes USEMEM, so we needn't do that here.)
 	 */
 	tuple = COPYTUP(state, tuple);
 
@@ -580,9 +581,8 @@ tuplestore_puttuple(Tuplestorestate *state, HeapTuple tuple)
 }
 
 /*
- * Similar to tuplestore_puttuple(), but start from the values + nulls
- * array. This avoids requiring that the caller construct a HeapTuple,
- * saving a copy.
+ * Similar to tuplestore_puttuple(), but work from values + nulls arrays.
+ * This avoids an extra tuple-construction operation.
  */
 void
 tuplestore_putvalues(Tuplestorestate *state, TupleDesc tdesc,
@@ -592,6 +592,7 @@ tuplestore_putvalues(Tuplestorestate *state, TupleDesc tdesc,
 	MemoryContext oldcxt = MemoryContextSwitchTo(state->context);
 
 	tuple = heap_form_minimal_tuple(tdesc, values, isnull);
+	USEMEM(state, GetMemoryChunkSpace(tuple));
 
 	tuplestore_puttuple_common(state, (void *) tuple);
 
-- 
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