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The original implementation of TABLESAMPLE modeled the tablesample method API on index access methods, which wasn't a good choice because, without specialized DDL commands, there's no way to build an extension that can implement a TSM. (Raw inserts into system catalogs are not an acceptable thing to do, because we can't undo them during DROP EXTENSION, nor will pg_upgrade behave sanely.) Instead adopt an API more like procedural language handlers or foreign data wrappers, wherein the only SQL-level support object needed is a single handler function identified by having a special return type. This lets us get rid of the supporting catalog altogether, so that no custom DDL support is needed for the feature. Adjust the API so that it can support non-constant tablesample arguments (the original coding assumed we could evaluate the argument expressions at ExecInitSampleScan time, which is undesirable even if it weren't outright unsafe), and discourage sampling methods from looking at invisible tuples. Make sure that the BERNOULLI and SYSTEM methods are genuinely repeatable within and across queries, as required by the SQL standard, and deal more honestly with methods that can't support that requirement. Make a full code-review pass over the tablesample additions, and fix assorted bugs, omissions, infelicities, and cosmetic issues (such as failure to put the added code stanzas in a consistent ordering). Improve EXPLAIN's output of tablesample plans, too. Back-patch to 9.5 so that we don't have to support the original API in production.
197 lines
5.8 KiB
C
197 lines
5.8 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) 1996-2015, 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 intentionally 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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REPLORIGIDENT,
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REPLORIGNAME,
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RULERELNAME,
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STATRELATTINH,
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TABLESPACEOID,
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TRFOID,
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TRFTYPELANG,
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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 relid);
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extern bool RelationHasSysCache(Oid relid);
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extern bool RelationSupportsSysCache(Oid relid);
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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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