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Commit6a17826

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Change hashscan.c to keep its list of active hash index scans in
TopMemoryContext, rather than scattered through executor per-query contexts.This poses no danger of memory leak since the ResourceOwner mechanismguarantees release of no-longer-needed items. It is needed because theper-query context might already be released by the time we try to clean upthe 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 rearrangedtransaction abort processing somehow; but this coding is undoubtedly riskyso I'll patch 8.0 and 8.1 anyway.
1 parentb2facfd commit6a17826

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‎src/backend/access/hash/hashscan.c

Lines changed: 20 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -8,17 +8,28 @@
88
*
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*
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* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/access/hash/hashscan.c,v 1.43 2008/01/01 19:45:46 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/hash/hashscan.c,v 1.44 2008/03/07 15:59:03 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include"postgres.h"
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#include"access/hash.h"
19+
#include"utils/memutils.h"
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#include"utils/resowner.h"
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/*
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* We track all of a backend's active scans on hash indexes using a list
25+
* of HashScanListData structs, which are allocated in TopMemoryContext.
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* It's okay to use a long-lived context because we rely on the ResourceOwner
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* mechanism to clean up unused entries after transaction or subtransaction
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* abort. We can't safely keep the entries in the executor's per-query
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* context, because that might be already freed before we get a chance to
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* clean up the list. (XXX seems like there should be a better way to
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* manage this...)
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*/
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typedefstructHashScanListData
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{
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IndexScanDeschashsl_scan;
@@ -44,6 +55,11 @@ ReleaseResources_hash(void)
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HashScanListnext;
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/*
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* Release all HashScanList items belonging to the current ResourceOwner.
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* Note that we do not release the underlying IndexScanDesc; that's in
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* executor memory and will go away on its own (in fact quite possibly
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* has gone away already, so we mustn't try to touch it here).
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*
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* Note: this should be a no-op during normal query shutdown. However, in
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* an abort situation ExecutorEnd is not called and so there may be open
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* index scans to clean up.
@@ -69,14 +85,15 @@ ReleaseResources_hash(void)
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}
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/*
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*_Hash_regscan() -- register a new scan.
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*_hash_regscan() -- register a new scan.
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*/
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void
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_hash_regscan(IndexScanDescscan)
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{
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HashScanListnew_el;
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79-
new_el= (HashScanList)palloc(sizeof(HashScanListData));
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new_el= (HashScanList)MemoryContextAlloc(TopMemoryContext,
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sizeof(HashScanListData));
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new_el->hashsl_scan=scan;
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new_el->hashsl_owner=CurrentResourceOwner;
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new_el->hashsl_next=HashScans;

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