src/include/utils/catcache.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * catcache.h
   4  *        Low-level catalog cache definitions.
   5  *
   6  * NOTE: every catalog cache must have a corresponding unique index on
   7  * the system table that it caches --- ie, the index must match the keys
   8  * used to do lookups in this cache.  All cache fetches are done with
   9  * indexscans (under normal conditions).  The index should be unique to
  10  * guarantee that there can only be one matching row for a key combination.
  11  *
  12  *
  13  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  14  * Portions Copyright (c) 1994, Regents of the University of California
  15  *
  16  * $PostgreSQL$
  17  *
  18  *-------------------------------------------------------------------------
  19  */
  20 #ifndef CATCACHE_H
  21 #define CATCACHE_H
  22
  23 #include "access/htup.h"
  24 #include "access/skey.h"
  25 #include "lib/dllist.h"
  26 #include "utils/relcache.h"
  27
  28 /*
  29  *              struct catctup:                 individual tuple in the cache.
  30  *              struct catclist:                list of tuples matching a partial key.
  31  *              struct catcache:                information for managing a cache.
  32  *              struct catcacheheader:  information for managing all the caches.
  33  */
  34
  35 typedef struct catcache
  36 {
  37         int                     id;                             /* cache identifier --- see syscache.h */
  38         struct catcache *cc_next;       /* link to next catcache */
  39         const char *cc_relname;         /* name of relation the tuples come from */
  40         Oid                     cc_reloid;              /* OID of relation the tuples come from */
  41         Oid                     cc_indexoid;    /* OID of index matching cache keys */
  42         bool            cc_relisshared; /* is relation shared across databases? */
  43         TupleDesc       cc_tupdesc;             /* tuple descriptor (copied from reldesc) */
  44         int                     cc_reloidattr;  /* AttrNumber of relation OID attr, or 0 */
  45         int                     cc_ntup;                /* # of tuples currently in this cache */
  46         int                     cc_nbuckets;    /* # of hash buckets in this cache */
  47         int                     cc_nkeys;               /* # of keys (1..4) */
  48         int                     cc_key[4];              /* AttrNumber of each key */
  49         PGFunction      cc_hashfunc[4]; /* hash function to use for each key */
  50         ScanKeyData cc_skey[4];         /* precomputed key info for heap scans */
  51         bool            cc_isname[4];   /* flag key columns that are NAMEs */
  52         Dllist          cc_lists;               /* list of CatCList structs */
  53 #ifdef CATCACHE_STATS
  54         long            cc_searches;    /* total # searches against this cache */
  55         long            cc_hits;                /* # of matches against existing entry */
  56         long            cc_neg_hits;    /* # of matches against negative entry */
  57         long            cc_newloads;    /* # of successful loads of new entry */
  58
  59         /*
  60          * cc_searches - (cc_hits + cc_neg_hits + cc_newloads) is number of failed
  61          * searches, each of which will result in loading a negative entry
  62          */
  63         long            cc_invals;              /* # of entries invalidated from cache */
  64         long            cc_lsearches;   /* total # list-searches */
  65         long            cc_lhits;               /* # of matches against existing lists */
  66 #endif
  67         Dllist          cc_bucket[1];   /* hash buckets --- VARIABLE LENGTH ARRAY */
  68 } CatCache;                                             /* VARIABLE LENGTH STRUCT */
  69
  70
  71 typedef struct catctup
  72 {
  73         int                     ct_magic;               /* for identifying CatCTup entries */
  74 #define CT_MAGIC   0x57261502
  75         CatCache   *my_cache;           /* link to owning catcache */
  76
  77         /*
  78          * Each tuple in a cache is a member of a Dllist that stores the elements
  79          * of its hash bucket.  We keep each Dllist in LRU order to speed repeated
  80          * lookups.
  81          */
  82         Dlelem          cache_elem;             /* list member of per-bucket list */
  83
  84         /*
  85          * The tuple may also be a member of at most one CatCList.      (If a single
  86          * catcache is list-searched with varying numbers of keys, we may have to
  87          * make multiple entries for the same tuple because of this restriction.
  88          * Currently, that's not expected to be common, so we accept the potential
  89          * inefficiency.)
  90          */
  91         struct catclist *c_list;        /* containing CatCList, or NULL if none */
  92
  93         /*
  94          * A tuple marked "dead" must not be returned by subsequent searches.
  95          * However, it won't be physically deleted from the cache until its
  96          * refcount goes to zero.  (If it's a member of a CatCList, the list's
  97          * refcount must go to zero, too; also, remember to mark the list dead at
  98          * the same time the tuple is marked.)
  99          *
 100          * A negative cache entry is an assertion that there is no tuple matching
 101          * a particular key.  This is just as useful as a normal entry so far as
 102          * avoiding catalog searches is concerned.      Management of positive and
 103          * negative entries is identical.
 104          */
 105         int                     refcount;               /* number of active references */
 106         bool            dead;                   /* dead but not yet removed? */
 107         bool            negative;               /* negative cache entry? */
 108         uint32          hash_value;             /* hash value for this tuple's keys */
 109         HeapTupleData tuple;            /* tuple management header */
 110 } CatCTup;
 111
 112
 113 typedef struct catclist
 114 {
 115         int                     cl_magic;               /* for identifying CatCList entries */
 116 #define CL_MAGIC   0x52765103
 117         CatCache   *my_cache;           /* link to owning catcache */
 118
 119         /*
 120          * A CatCList describes the result of a partial search, ie, a search using
 121          * only the first K key columns of an N-key cache.      We form the keys used
 122          * into a tuple (with other attributes NULL) to represent the stored key
 123          * set.  The CatCList object contains links to cache entries for all the
 124          * table rows satisfying the partial key.  (Note: none of these will be
 125          * negative cache entries.)
 126          *
 127          * A CatCList is only a member of a per-cache list; we do not currently
 128          * divide them into hash buckets.
 129          *
 130          * A list marked "dead" must not be returned by subsequent searches.
 131          * However, it won't be physically deleted from the cache until its
 132          * refcount goes to zero.  (A list should be marked dead if any of its
 133          * member entries are dead.)
 134          *
 135          * If "ordered" is true then the member tuples appear in the order of the
 136          * cache's underlying index.  This will be true in normal operation, but
 137          * might not be true during bootstrap or recovery operations. (namespace.c
 138          * is able to save some cycles when it is true.)
 139          */
 140         Dlelem          cache_elem;             /* list member of per-catcache list */
 141         int                     refcount;               /* number of active references */
 142         bool            dead;                   /* dead but not yet removed? */
 143         bool            ordered;                /* members listed in index order? */
 144         short           nkeys;                  /* number of lookup keys specified */
 145         uint32          hash_value;             /* hash value for lookup keys */
 146         HeapTupleData tuple;            /* header for tuple holding keys */
 147         int                     n_members;              /* number of member tuples */
 148         CatCTup    *members[1];         /* members --- VARIABLE LENGTH ARRAY */
 149 } CatCList;                                             /* VARIABLE LENGTH STRUCT */
 150
 151
 152 typedef struct catcacheheader
 153 {
 154         CatCache   *ch_caches;          /* head of list of CatCache structs */
 155         int                     ch_ntup;                /* # of tuples in all caches */
 156 } CatCacheHeader;
 157
 158
 159 /* this extern duplicates utils/memutils.h... */
 160 extern PGDLLIMPORT MemoryContext CacheMemoryContext;
 161
 162 extern void CreateCacheMemoryContext(void);
 163 extern void AtEOXact_CatCache(bool isCommit);
 164
 165 extern CatCache *InitCatCache(int id, Oid reloid, Oid indexoid,
 166                          int reloidattr,
 167                          int nkeys, const int *key,
 168                          int nbuckets);
 169 extern void InitCatCachePhase2(CatCache *cache, bool touch_index);
 170
 171 extern HeapTuple SearchCatCache(CatCache *cache,
 172                            Datum v1, Datum v2,
 173                            Datum v3, Datum v4);
 174 extern void ReleaseCatCache(HeapTuple tuple);
 175
 176 extern CatCList *SearchCatCacheList(CatCache *cache, int nkeys,
 177                                    Datum v1, Datum v2,
 178                                    Datum v3, Datum v4);
 179 extern void ReleaseCatCacheList(CatCList *list);
 180
 181 extern void ResetCatalogCaches(void);
 182 extern void CatalogCacheFlushRelation(Oid relId);
 183 extern void CatalogCacheIdInvalidate(int cacheId, uint32 hashValue,
 184                                                  ItemPointer pointer);
 185 extern void PrepareToInvalidateCacheTuple(Relation relation,
 186                                                           HeapTuple tuple,
 187                                                    void (*function) (int, uint32, ItemPointer, Oid));
 188
 189 extern void PrintCatCacheLeakWarning(HeapTuple tuple);
 190 extern void PrintCatCacheListLeakWarning(CatCList *list);
 191
 192 #endif   /* CATCACHE_H */