catcache.h

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * 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) 1996-2019, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/utils/catcache.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef CATCACHE_H
#define CATCACHE_H

#include "access/htup.h"
#include "access/skey.h"
#include "lib/ilist.h"
#include "utils/relcache.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.
 */

#define CATCACHE_MAXKEYS        4


/* function computing a datum's hash */
typedef uint32 (*CCHashFN) (Datum datum);

/* function computing equality of two datums */
typedef bool (*CCFastEqualFN) (Datum a, Datum b);

typedef struct catcache
{
    int         id;             /* cache identifier --- see syscache.h */
    int         cc_nbuckets;    /* # of hash buckets in this cache */
    TupleDesc   cc_tupdesc;     /* tuple descriptor (copied from reldesc) */
    dlist_head *cc_bucket;      /* hash buckets */
    CCHashFN    cc_hashfunc[CATCACHE_MAXKEYS];  /* hash function for each key */
    CCFastEqualFN cc_fastequal[CATCACHE_MAXKEYS];   /* fast equal function for
                                                     * each key */
    int         cc_keyno[CATCACHE_MAXKEYS]; /* AttrNumber of each key */
    dlist_head  cc_lists;       /* list of CatCList structs */
    int         cc_ntup;        /* # of tuples currently in this cache */
    int         cc_nkeys;       /* # of keys (1..CATCACHE_MAXKEYS) */
    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? */
    slist_node  cc_next;        /* list link */
    ScanKeyData cc_skey[CATCACHE_MAXKEYS];  /* precomputed key info for heap
                                             * scans */

    /*
     * Keep these at the end, so that compiling catcache.c with CATCACHE_STATS
     * doesn't break ABI for other modules
     */
#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_lsearches;   /* total # list-searches */
    long        cc_lhits;       /* # of matches against existing lists */
#endif
} CatCache;


typedef struct catctup
{
    int         ct_magic;       /* for identifying CatCTup entries */
#define CT_MAGIC   0x57261502

    uint32      hash_value;     /* hash value for this tuple's keys */

    /*
     * Lookup keys for the entry. By-reference datums point into the tuple for
     * positive cache entries, and are separately allocated for negative ones.
     */
    Datum       keys[CATCACHE_MAXKEYS];

    /*
     * Each tuple in a cache is a member of a dlist that stores the elements
     * of its hash bucket.  We keep each dlist in LRU order to speed repeated
     * lookups.
     */
    dlist_node  cache_elem;     /* list member of per-bucket list */

    /*
     * 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? */
    HeapTupleData tuple;        /* tuple management header */

    /*
     * 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 */

    CatCache   *my_cache;       /* link to owning catcache */
    /* properly aligned tuple data follows, unless a negative entry */
} CatCTup;


/*
 * 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 store the keys used
 * into the keys attribute 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 currently
 * divide them into hash buckets.
 *
 * 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.)
 */
typedef struct catclist
{
    int         cl_magic;       /* for identifying CatCList entries */
#define CL_MAGIC   0x52765103

    uint32      hash_value;     /* hash value for lookup keys */

    dlist_node  cache_elem;     /* list member of per-catcache list */

    /*
     * Lookup keys for the entry, with the first nkeys elements being valid.
     * All by-reference are separately allocated.
     */
    Datum       keys[CATCACHE_MAXKEYS];

    int         refcount;       /* number of active references */
    bool        dead;           /* dead but not yet removed? */
    bool        ordered;        /* members listed in index order? */
    short       nkeys;          /* number of lookup keys specified */
    int         n_members;      /* number of member tuples */
    CatCache   *my_cache;       /* link to owning catcache */
    CatCTup    *members[FLEXIBLE_ARRAY_MEMBER]; /* members */
} CatCList;


typedef struct catcacheheader
{
    slist_head  ch_caches;      /* head of list of CatCache structs */
    int         ch_ntup;        /* # of tuples in all caches */
} CatCacheHeader;


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

extern void CreateCacheMemoryContext(void);

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

extern HeapTuple SearchCatCache(CatCache *cache,
                                Datum v1, Datum v2, Datum v3, Datum v4);
extern HeapTuple SearchCatCache1(CatCache *cache,
                                 Datum v1);
extern HeapTuple SearchCatCache2(CatCache *cache,
                                 Datum v1, Datum v2);
extern HeapTuple SearchCatCache3(CatCache *cache,
                                 Datum v1, Datum v2, Datum v3);
extern HeapTuple SearchCatCache4(CatCache *cache,
                                 Datum v1, Datum v2, Datum v3, Datum v4);
extern void ReleaseCatCache(HeapTuple tuple);

extern uint32 GetCatCacheHashValue(CatCache *cache,
                                   Datum v1, Datum v2,
                                   Datum v3, Datum v4);

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

extern void ResetCatalogCaches(void);
extern void CatalogCacheFlushCatalog(Oid catId);
extern void CatCacheInvalidate(CatCache *cache, uint32 hashValue);
extern void PrepareToInvalidateCacheTuple(Relation relation,
                                          HeapTuple tuple,
                                          HeapTuple newtuple,
                                          void (*function) (int, uint32, Oid));

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

#endif                          /* CATCACHE_H */