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Change hashscan.c to keep its list of active hash index scans in

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TopMemoryContext, rather than scattered through executor per-query contexts.
This poses no danger of memory leak since the ResourceOwner mechanism
guarantees release of no-longer-needed items.  It is needed because the
per-query context might already be released by the time we try to clean up
the hash scan list.  Report by ykhuang, diagnosis by Heikki.

Back-patch to 8.0, where the ResourceOwner-based cleanup was introduced.
The given test case does not fail before 8.2, probably because we rearranged
transaction abort processing somehow; but this coding is undoubtedly risky
so I'll patch 8.0 and 8.1 anyway.
This commit is contained in:
Tom Lane 2008-03-07 15:59:03 +00:00
parent b2facfd918
commit 6a17826621
1 changed files with 20 additions and 3 deletions
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23
src/backend/access/hash/hashscan.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/hash/hashscan.c,v 1.43 2008/01/01 19:45:46 momjian Exp $
* $PostgreSQL: pgsql/src/backend/access/hash/hashscan.c,v 1.44 2008/03/07 15:59:03 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -16,9 +16,20 @@
#include "postgres.h"
#include "access/hash.h"
#include "utils/memutils.h"
#include "utils/resowner.h"
/*
* We track all of a backend's active scans on hash indexes using a list
* of HashScanListData structs, which are allocated in TopMemoryContext.
* It's okay to use a long-lived context because we rely on the ResourceOwner
* mechanism to clean up unused entries after transaction or subtransaction
* abort. We can't safely keep the entries in the executor's per-query
* context, because that might be already freed before we get a chance to
* clean up the list. (XXX seems like there should be a better way to
* manage this...)
*/
typedef struct HashScanListData
{
IndexScanDesc hashsl_scan;
@ -44,6 +55,11 @@ ReleaseResources_hash(void)
HashScanList next;
/*
* Release all HashScanList items belonging to the current ResourceOwner.
* Note that we do not release the underlying IndexScanDesc; that's in
* executor memory and will go away on its own (in fact quite possibly
* has gone away already, so we mustn't try to touch it here).
*
* Note: this should be a no-op during normal query shutdown. However, in
* an abort situation ExecutorEnd is not called and so there may be open
* index scans to clean up.
@ -69,14 +85,15 @@ ReleaseResources_hash(void)
}
/*
* _Hash_regscan() -- register a new scan.
* _hash_regscan() -- register a new scan.
*/
void
_hash_regscan(IndexScanDesc scan)
{
HashScanList new_el;
new_el = (HashScanList) palloc(sizeof(HashScanListData));
new_el = (HashScanList) MemoryContextAlloc(TopMemoryContext,
sizeof(HashScanListData));
new_el->hashsl_scan = scan;
new_el->hashsl_owner = CurrentResourceOwner;
new_el->hashsl_next = HashScans;