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Fix possible failures when a tuplestore switches from in-memory to on-disk

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mode while callers hold pointers to in-memory tuples.  I reported this for
the case of nodeWindowAgg's primary scan tuple, but inspection of the code
shows that all of the calls in nodeWindowAgg and nodeCtescan are at risk.
For the moment, fix it with a rather brute-force approach of copying
whenever one of the at-risk callers requests a tuple.  Later we might
think of some sort of reference-count approach to reduce tuple copying.
This commit is contained in:
Tom Lane
2009-03-27 18:30:21 +00:00
parent a95307b639
commit 25bf7f8b9b
10 changed files with 53 additions and 25 deletions
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8
src/backend/executor/nodeCtescan.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/nodeCtescan.c,v 1.3 2009/01/01 17:23:41 momjian Exp $
* $PostgreSQL: pgsql/src/backend/executor/nodeCtescan.c,v 1.4 2009/03/27 18:30:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -71,10 +71,14 @@ CteScanNext(CteScanState *node)
/*
* If we can fetch another tuple from the tuplestore, return it.
*
* Note: we have to use copy=true in the tuplestore_gettupleslot call,
* because we are sharing the tuplestore with other nodes that might
* write into the tuplestore before we get called again.
*/
if (!eof_tuplestore)
{
if (tuplestore_gettupleslot(tuplestorestate, forward, slot))
if (tuplestore_gettupleslot(tuplestorestate, forward, true, slot))
return slot;
if (forward)
eof_tuplestore = true;