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568d4138c6
SnapshotNow scans have the undesirable property that, in the face of concurrent updates, the scan can fail to see either the old or the new versions of the row. In many cases, we work around this by requiring DDL operations to hold AccessExclusiveLock on the object being modified; in some cases, the existing locking is inadequate and random failures occur as a result. This commit doesn't change anything related to locking, but will hopefully pave the way to allowing lock strength reductions in the future. The major issue has held us back from making this change in the past is that taking an MVCC snapshot is significantly more expensive than using a static special snapshot such as SnapshotNow. However, testing of various worst-case scenarios reveals that this problem is not severe except under fairly extreme workloads. To mitigate those problems, we avoid retaking the MVCC snapshot for each new scan; instead, we take a new snapshot only when invalidation messages have been processed. The catcache machinery already requires that invalidation messages be sent before releasing the related heavyweight lock; else other backends might rely on locally-cached data rather than scanning the catalog at all. Thus, making snapshot reuse dependent on the same guarantees shouldn't break anything that wasn't already subtly broken. Patch by me. Review by Michael Paquier and Andres Freund.
193 lines
5.7 KiB
C
193 lines
5.7 KiB
C
/*-------------------------------------------------------------------------
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*
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* syscache.h
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* System catalog cache definitions.
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*
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* See also lsyscache.h, which provides convenience routines for
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* common cache-lookup operations.
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*
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* Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/utils/syscache.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef SYSCACHE_H
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#define SYSCACHE_H
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#include "access/attnum.h"
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#include "access/htup.h"
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/* we purposedly do not include utils/catcache.h here */
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/*
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* SysCache identifiers.
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*
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* The order of these identifiers must match the order
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* of the entries in the array cacheinfo[] in syscache.c.
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* Keep them in alphabetical order (renumbering only costs a
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* backend rebuild).
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*/
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enum SysCacheIdentifier
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{
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AGGFNOID = 0,
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AMNAME,
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AMOID,
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AMOPOPID,
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AMOPSTRATEGY,
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AMPROCNUM,
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ATTNAME,
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ATTNUM,
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AUTHMEMMEMROLE,
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AUTHMEMROLEMEM,
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AUTHNAME,
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AUTHOID,
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CASTSOURCETARGET,
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CLAAMNAMENSP,
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CLAOID,
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COLLNAMEENCNSP,
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COLLOID,
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CONDEFAULT,
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CONNAMENSP,
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CONSTROID,
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CONVOID,
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DATABASEOID,
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DEFACLROLENSPOBJ,
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ENUMOID,
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ENUMTYPOIDNAME,
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EVENTTRIGGERNAME,
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EVENTTRIGGEROID,
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FOREIGNDATAWRAPPERNAME,
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FOREIGNDATAWRAPPEROID,
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FOREIGNSERVERNAME,
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FOREIGNSERVEROID,
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FOREIGNTABLEREL,
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INDEXRELID,
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LANGNAME,
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LANGOID,
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NAMESPACENAME,
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NAMESPACEOID,
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OPERNAMENSP,
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OPEROID,
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OPFAMILYAMNAMENSP,
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OPFAMILYOID,
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PROCNAMEARGSNSP,
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PROCOID,
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RANGETYPE,
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RELNAMENSP,
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RELOID,
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RULERELNAME,
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STATRELATTINH,
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TABLESPACEOID,
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TSCONFIGMAP,
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TSCONFIGNAMENSP,
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TSCONFIGOID,
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TSDICTNAMENSP,
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TSDICTOID,
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TSPARSERNAMENSP,
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TSPARSEROID,
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TSTEMPLATENAMENSP,
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TSTEMPLATEOID,
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TYPENAMENSP,
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TYPEOID,
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USERMAPPINGOID,
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USERMAPPINGUSERSERVER
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};
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extern void InitCatalogCache(void);
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extern void InitCatalogCachePhase2(void);
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extern HeapTuple SearchSysCache(int cacheId,
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Datum key1, Datum key2, Datum key3, Datum key4);
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extern void ReleaseSysCache(HeapTuple tuple);
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/* convenience routines */
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extern HeapTuple SearchSysCacheCopy(int cacheId,
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Datum key1, Datum key2, Datum key3, Datum key4);
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extern bool SearchSysCacheExists(int cacheId,
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Datum key1, Datum key2, Datum key3, Datum key4);
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extern Oid GetSysCacheOid(int cacheId,
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Datum key1, Datum key2, Datum key3, Datum key4);
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extern HeapTuple SearchSysCacheAttName(Oid relid, const char *attname);
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extern HeapTuple SearchSysCacheCopyAttName(Oid relid, const char *attname);
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extern bool SearchSysCacheExistsAttName(Oid relid, const char *attname);
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extern Datum SysCacheGetAttr(int cacheId, HeapTuple tup,
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AttrNumber attributeNumber, bool *isNull);
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extern uint32 GetSysCacheHashValue(int cacheId,
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Datum key1, Datum key2, Datum key3, Datum key4);
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/* list-search interface. Users of this must import catcache.h too */
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struct catclist;
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extern struct catclist *SearchSysCacheList(int cacheId, int nkeys,
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Datum key1, Datum key2, Datum key3, Datum key4);
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extern bool RelationInvalidatesSnapshotsOnly(Oid);
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extern bool RelationHasSysCache(Oid);
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/*
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* The use of the macros below rather than direct calls to the corresponding
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* functions is encouraged, as it insulates the caller from changes in the
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* maximum number of keys.
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*/
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#define SearchSysCache1(cacheId, key1) \
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SearchSysCache(cacheId, key1, 0, 0, 0)
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#define SearchSysCache2(cacheId, key1, key2) \
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SearchSysCache(cacheId, key1, key2, 0, 0)
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#define SearchSysCache3(cacheId, key1, key2, key3) \
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SearchSysCache(cacheId, key1, key2, key3, 0)
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#define SearchSysCache4(cacheId, key1, key2, key3, key4) \
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SearchSysCache(cacheId, key1, key2, key3, key4)
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#define SearchSysCacheCopy1(cacheId, key1) \
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SearchSysCacheCopy(cacheId, key1, 0, 0, 0)
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#define SearchSysCacheCopy2(cacheId, key1, key2) \
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SearchSysCacheCopy(cacheId, key1, key2, 0, 0)
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#define SearchSysCacheCopy3(cacheId, key1, key2, key3) \
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SearchSysCacheCopy(cacheId, key1, key2, key3, 0)
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#define SearchSysCacheCopy4(cacheId, key1, key2, key3, key4) \
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SearchSysCacheCopy(cacheId, key1, key2, key3, key4)
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#define SearchSysCacheExists1(cacheId, key1) \
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SearchSysCacheExists(cacheId, key1, 0, 0, 0)
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#define SearchSysCacheExists2(cacheId, key1, key2) \
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SearchSysCacheExists(cacheId, key1, key2, 0, 0)
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#define SearchSysCacheExists3(cacheId, key1, key2, key3) \
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SearchSysCacheExists(cacheId, key1, key2, key3, 0)
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#define SearchSysCacheExists4(cacheId, key1, key2, key3, key4) \
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SearchSysCacheExists(cacheId, key1, key2, key3, key4)
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#define GetSysCacheOid1(cacheId, key1) \
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GetSysCacheOid(cacheId, key1, 0, 0, 0)
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#define GetSysCacheOid2(cacheId, key1, key2) \
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GetSysCacheOid(cacheId, key1, key2, 0, 0)
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#define GetSysCacheOid3(cacheId, key1, key2, key3) \
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GetSysCacheOid(cacheId, key1, key2, key3, 0)
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#define GetSysCacheOid4(cacheId, key1, key2, key3, key4) \
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GetSysCacheOid(cacheId, key1, key2, key3, key4)
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#define GetSysCacheHashValue1(cacheId, key1) \
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GetSysCacheHashValue(cacheId, key1, 0, 0, 0)
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#define GetSysCacheHashValue2(cacheId, key1, key2) \
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GetSysCacheHashValue(cacheId, key1, key2, 0, 0)
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#define GetSysCacheHashValue3(cacheId, key1, key2, key3) \
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GetSysCacheHashValue(cacheId, key1, key2, key3, 0)
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#define GetSysCacheHashValue4(cacheId, key1, key2, key3, key4) \
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GetSysCacheHashValue(cacheId, key1, key2, key3, key4)
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#define SearchSysCacheList1(cacheId, key1) \
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SearchSysCacheList(cacheId, 1, key1, 0, 0, 0)
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#define SearchSysCacheList2(cacheId, key1, key2) \
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SearchSysCacheList(cacheId, 2, key1, key2, 0, 0)
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#define SearchSysCacheList3(cacheId, key1, key2, key3) \
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SearchSysCacheList(cacheId, 3, key1, key2, key3, 0)
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#define SearchSysCacheList4(cacheId, key1, key2, key3, key4) \
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SearchSysCacheList(cacheId, 4, key1, key2, key3, key4)
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#define ReleaseSysCacheList(x) ReleaseCatCacheList(x)
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#endif /* SYSCACHE_H */
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