src/libpq/include/utils/catcache.h

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/*-------------------------------------------------------------------------
 *
 * catcache.h
 *        Low-level catalog cache definitions.
 *
 * NOTE: every catalog cache must have a corresponding unique index on
 * the system table that it caches --- ie, the index must match the keys
 * used to do lookups in this cache.  All cache fetches are done with
 * indexscans (under normal conditions).  The index should be unique to
 * guarantee that there can only be one matching row for a key combination.
 *
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * $PostgreSQL: pgsql/src/include/utils/catcache.h,v 1.56.2.1 2005/11/22 18:23:29 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef CATCACHE_H
#define CATCACHE_H

#include "access/htup.h"
#include "access/skey.h"
#include "lib/dllist.h"

/*
 *              struct catctup:                 individual tuple in the cache.
 *              struct catclist:                list of tuples matching a partial key.
 *              struct catcache:                information for managing a cache.
 *              struct catcacheheader:  information for managing all the caches.
 */

typedef struct catcache
{
        int                     id;                             /* cache identifier --- see syscache.h */
        struct catcache *cc_next;       /* link to next catcache */
        const char *cc_relname;         /* name of relation the tuples come from */
        Oid                     cc_reloid;              /* OID of relation the tuples come from */
        Oid                     cc_indexoid;    /* OID of index matching cache keys */
        bool            cc_relisshared; /* is relation shared across databases? */
        TupleDesc       cc_tupdesc;             /* tuple descriptor (copied from reldesc) */
        int                     cc_reloidattr;  /* AttrNumber of relation OID attr, or 0 */
        int                     cc_ntup;                /* # of tuples currently in this cache */
        int                     cc_nbuckets;    /* # of hash buckets in this cache */
        int                     cc_nkeys;               /* # of keys (1..4) */
        int                     cc_key[4];              /* AttrNumber of each key */
        PGFunction      cc_hashfunc[4]; /* hash function to use for each key */
        ScanKeyData cc_skey[4];         /* precomputed key info for heap scans */
        bool            cc_isname[4];   /* flag key columns that are NAMEs */
        Dllist          cc_lists;               /* list of CatCList structs */
#ifdef CATCACHE_STATS
        long            cc_searches;    /* total # searches against this cache */
        long            cc_hits;                /* # of matches against existing entry */
        long            cc_neg_hits;    /* # of matches against negative entry */
        long            cc_newloads;    /* # of successful loads of new entry */

        /*
         * cc_searches - (cc_hits + cc_neg_hits + cc_newloads) is number of failed
         * searches, each of which will result in loading a negative entry
         */
        long            cc_invals;              /* # of entries invalidated from cache */
        long            cc_discards;    /* # of entries discarded due to overflow */
        long            cc_lsearches;   /* total # list-searches */
        long            cc_lhits;               /* # of matches against existing lists */
#endif
        Dllist          cc_bucket[1];   /* hash buckets --- VARIABLE LENGTH ARRAY */
} CatCache;                                             /* VARIABLE LENGTH STRUCT */


typedef struct catctup
{
        int                     ct_magic;               /* for identifying CatCTup entries */
#define CT_MAGIC   0x57261502
        CatCache   *my_cache;           /* link to owning catcache */

        /*
         * Each tuple in a cache is a member of two Dllists: one lists all the
         * elements in all the caches in LRU order, and the other lists just the
         * elements in one hashbucket of one cache, also in LRU order.
         */
        Dlelem          lrulist_elem;   /* list member of global LRU list */
        Dlelem          cache_elem;             /* list member of per-bucket list */

        /*
         * The tuple may also be a member of at most one CatCList.      (If a single
         * catcache is list-searched with varying numbers of keys, we may have to
         * make multiple entries for the same tuple because of this restriction.
         * Currently, that's not expected to be common, so we accept the potential
         * inefficiency.)
         */
        struct catclist *c_list;        /* containing CatCList, or NULL if none */

        /*
         * A tuple marked "dead" must not be returned by subsequent searches.
         * However, it won't be physically deleted from the cache until its
         * refcount goes to zero.  (If it's a member of a CatCList, the list's
         * refcount must go to zero, too; also, remember to mark the list dead at
         * the same time the tuple is marked.)
         *
         * A negative cache entry is an assertion that there is no tuple matching
         * a particular key.  This is just as useful as a normal entry so far as
         * avoiding catalog searches is concerned.      Management of positive and
         * negative entries is identical.
         */
        int                     refcount;               /* number of active references */
        bool            dead;                   /* dead but not yet removed? */
        bool            negative;               /* negative cache entry? */
        uint32          hash_value;             /* hash value for this tuple's keys */
        HeapTupleData tuple;            /* tuple management header */
} CatCTup;


typedef struct catclist
{
        int                     cl_magic;               /* for identifying CatCList entries */
#define CL_MAGIC   0x52765103
        CatCache   *my_cache;           /* link to owning catcache */

        /*
         * A CatCList describes the result of a partial search, ie, a search using
         * only the first K key columns of an N-key cache.      We form the keys used
         * into a tuple (with other attributes NULL) to represent the stored key
         * set.  The CatCList object contains links to cache entries for all the
         * table rows satisfying the partial key.  (Note: none of these will be
         * negative cache entries.)
         *
         * A CatCList is only a member of a per-cache list; we do not do separate
         * LRU management for CatCLists.  See CatalogCacheCleanup() for the
         * details of the management algorithm.
         *
         * A list marked "dead" must not be returned by subsequent searches.
         * However, it won't be physically deleted from the cache until its
         * refcount goes to zero.  (A list should be marked dead if any of its
         * member entries are dead.)
         *
         * If "ordered" is true then the member tuples appear in the order of the
         * cache's underlying index.  This will be true in normal operation, but
         * might not be true during bootstrap or recovery operations. (namespace.c
         * is able to save some cycles when it is true.)
         */
        Dlelem          cache_elem;             /* list member of per-catcache list */
        int                     refcount;               /* number of active references */
        bool            dead;                   /* dead but not yet removed? */
        bool            ordered;                /* members listed in index order? */
        bool            touched;                /* used since last CatalogCacheCleanup? */
        short           nkeys;                  /* number of lookup keys specified */
        uint32          hash_value;             /* hash value for lookup keys */
        HeapTupleData tuple;            /* header for tuple holding keys */
        int                     n_members;              /* number of member tuples */
        CatCTup    *members[1];         /* members --- VARIABLE LENGTH ARRAY */
} CatCList;                                             /* VARIABLE LENGTH STRUCT */


typedef struct catcacheheader
{
        CatCache   *ch_caches;          /* head of list of CatCache structs */
        int                     ch_ntup;                /* # of tuples in all caches */
        int                     ch_maxtup;              /* max # of tuples allowed (LRU) */
        Dllist          ch_lrulist;             /* overall LRU list, most recent first */
} CatCacheHeader;


/* this extern duplicates utils/memutils.h... */
extern DLLIMPORT MemoryContext CacheMemoryContext;

extern void CreateCacheMemoryContext(void);
extern void AtEOXact_CatCache(bool isCommit);

extern CatCache *InitCatCache(int id, Oid reloid, Oid indexoid,
                         int reloidattr,
                         int nkeys, const int *key);
extern void InitCatCachePhase2(CatCache *cache);

extern HeapTuple SearchCatCache(CatCache *cache,
                           Datum v1, Datum v2,
                           Datum v3, Datum v4);
extern void ReleaseCatCache(HeapTuple tuple);

extern CatCList *SearchCatCacheList(CatCache *cache, int nkeys,
                                   Datum v1, Datum v2,
                                   Datum v3, Datum v4);
extern void ReleaseCatCacheList(CatCList *list);

extern void ResetCatalogCaches(void);
extern void CatalogCacheFlushRelation(Oid relId);
extern void CatalogCacheIdInvalidate(int cacheId, uint32 hashValue,
                                                 ItemPointer pointer);
extern void PrepareToInvalidateCacheTuple(Relation relation,
                                                          HeapTuple tuple,
                                                   void (*function) (int, uint32, ItemPointer, Oid));

extern void PrintCatCacheLeakWarning(HeapTuple tuple);
extern void PrintCatCacheListLeakWarning(CatCList *list);

#endif   /* CATCACHE_H */