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Commitaf73e37

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Cope with inplace update making catcache stale during TOAST fetch.
This extendsad98fb1 to invals ofinplace updates. Trouble requires an inplace update of a catalog havinga TOAST table, so only pg_database was at risk. (The other catalog onwhich core code performs inplace updates, pg_class, has no TOAST table.)Trouble would require something like the inplace-inval.spec test.Consider GRANT ... ON DATABASE fetching a stale row from cache anddiscarding a datfrozenxid update that vac_truncate_clog() has alreadyrelied upon. Back-patch to v12 (all supported versions).Reviewed (in an earlier version) by Robert Haas.Discussion:https://postgr.es/m/20240114201411.d0@rfd.leadboat.comDiscussion:https://postgr.es/m/20240512232923.aa.nmisch@google.com
1 parente038b77 commitaf73e37

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3 files changed

+64
-3
lines changed

3 files changed

+64
-3
lines changed

‎src/backend/catalog/catalog.c

Lines changed: 21 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -135,6 +135,27 @@ IsCatalogRelationOid(Oid relid)
135135
return (relid< (Oid)FirstBootstrapObjectId);
136136
}
137137

138+
/*
139+
* IsInplaceUpdateRelation
140+
*True iff core code performs inplace updates on the relation.
141+
*/
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bool
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IsInplaceUpdateRelation(Relationrelation)
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{
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returnIsInplaceUpdateOid(RelationGetRelid(relation));
146+
}
147+
148+
/*
149+
* IsInplaceUpdateOid
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*Like the above, but takes an OID as argument.
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*/
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bool
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IsInplaceUpdateOid(Oidrelid)
154+
{
155+
return (relid==RelationRelationId||
156+
relid==DatabaseRelationId);
157+
}
158+
138159
/*
139160
* IsToastRelation
140161
*True iff relation is a TOAST support relation (or index).

‎src/backend/utils/cache/catcache.c

Lines changed: 41 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -21,6 +21,7 @@
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#include"access/table.h"
2222
#include"access/valid.h"
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#include"access/xact.h"
24+
#include"catalog/catalog.h"
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#include"catalog/pg_collation.h"
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#include"catalog/pg_operator.h"
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#include"catalog/pg_type.h"
@@ -1849,6 +1850,23 @@ ReleaseCatCacheList(CatCList *list)
18491850
}
18501851

18511852

1853+
/*
1854+
* equalTuple
1855+
*Are these tuples memcmp()-equal?
1856+
*/
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staticbool
1858+
equalTuple(HeapTuplea,HeapTupleb)
1859+
{
1860+
uint32alen;
1861+
uint32blen;
1862+
1863+
alen=a->t_len;
1864+
blen=b->t_len;
1865+
return (alen==blen&&
1866+
memcmp((char*)a->t_data,
1867+
(char*)b->t_data,blen)==0);
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}
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18521870
/*
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* CatalogCacheCreateEntry
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*Create a new CatCTup entry, copying the given HeapTuple and other
@@ -1899,14 +1917,34 @@ CatalogCacheCreateEntry(CatCache *cache, HeapTuple ntp, SysScanDesc scandesc,
18991917
*/
19001918
if (HeapTupleHasExternal(ntp))
19011919
{
1920+
boolneed_cmp=IsInplaceUpdateOid(cache->cc_reloid);
1921+
HeapTuplebefore=NULL;
1922+
boolmatches= true;
1923+
1924+
if (need_cmp)
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before=heap_copytuple(ntp);
19021926
dtp=toast_flatten_tuple(ntp,cache->cc_tupdesc);
19031927

19041928
/*
19051929
* The tuple could become stale while we are doing toast table
1906-
* access (since AcceptInvalidationMessages can run then), so we
1907-
* must recheck its visibility afterwards.
1930+
* access (since AcceptInvalidationMessages can run then).
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* equalTuple() detects staleness from inplace updates, while
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* systable_recheck_tuple() detects staleness from normal updates.
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*
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* While this equalTuple() follows the usual rule of reading with
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* a pin and no buffer lock, it warrants suspicion since an
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* inplace update could appear at any moment. It's safe because
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* the inplace update sends an invalidation that can't reorder
1938+
* before the inplace heap change. If the heap change reaches
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* this process just after equalTuple() looks, we've not missed
1940+
* its inval.
19081941
*/
1909-
if (!systable_recheck_tuple(scandesc,ntp))
1942+
if (need_cmp)
1943+
{
1944+
matches=equalTuple(before,ntp);
1945+
heap_freetuple(before);
1946+
}
1947+
if (!matches|| !systable_recheck_tuple(scandesc,ntp))
19101948
{
19111949
heap_freetuple(dtp);
19121950
returnNULL;

‎src/include/catalog/catalog.h

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -21,11 +21,13 @@
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externboolIsSystemRelation(Relationrelation);
2222
externboolIsToastRelation(Relationrelation);
2323
externboolIsCatalogRelation(Relationrelation);
24+
externboolIsInplaceUpdateRelation(Relationrelation);
2425

2526
externboolIsSystemClass(Oidrelid,Form_pg_classreltuple);
2627
externboolIsToastClass(Form_pg_classreltuple);
2728

2829
externboolIsCatalogRelationOid(Oidrelid);
30+
externboolIsInplaceUpdateOid(Oidrelid);
2931

3032
externboolIsCatalogNamespace(OidnamespaceId);
3133
externboolIsToastNamespace(OidnamespaceId);

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