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) 1996-2022, PostgreSQL Global Development Group
  14  * Portions Copyright (c) 1994, Regents of the University of California
  15  *
  16  * src/include/utils/catcache.h
  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/ilist.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 #define CATCACHE_MAXKEYS                4
  36
  37
  38 /* function computing a datum's hash */
  39 typedef uint32 (*CCHashFN) (Datum datum);
  40
  41 /* function computing equality of two datums */
  42 typedef bool (*CCFastEqualFN) (Datum a, Datum b);
  43
  44 typedef struct catcache
  45 {
  46         int                     id;                             /* cache identifier --- see syscache.h */
  47         int                     cc_nbuckets;    /* # of hash buckets in this cache */
  48         TupleDesc       cc_tupdesc;             /* tuple descriptor (copied from reldesc) */
  49         dlist_head *cc_bucket;          /* hash buckets */
  50         CCHashFN        cc_hashfunc[CATCACHE_MAXKEYS];  /* hash function for each key */
  51         CCFastEqualFN cc_fastequal[CATCACHE_MAXKEYS];   /* fast equal function for
  52                                                                                                          * each key */
  53         int                     cc_keyno[CATCACHE_MAXKEYS]; /* AttrNumber of each key */
  54         dlist_head      cc_lists;               /* list of CatCList structs */
  55         int                     cc_ntup;                /* # of tuples currently in this cache */
  56         int                     cc_nkeys;               /* # of keys (1..CATCACHE_MAXKEYS) */
  57         const char *cc_relname;         /* name of relation the tuples come from */
  58         Oid                     cc_reloid;              /* OID of relation the tuples come from */
  59         Oid                     cc_indexoid;    /* OID of index matching cache keys */
  60         bool            cc_relisshared; /* is relation shared across databases? */
  61         slist_node      cc_next;                /* list link */
  62         ScanKeyData cc_skey[CATCACHE_MAXKEYS];  /* precomputed key info for heap
  63                                                                                          * scans */
  64
  65         /*
  66          * Keep these at the end, so that compiling catcache.c with CATCACHE_STATS
  67          * doesn't break ABI for other modules
  68          */
  69 #ifdef CATCACHE_STATS
  70         long            cc_searches;    /* total # searches against this cache */
  71         long            cc_hits;                /* # of matches against existing entry */
  72         long            cc_neg_hits;    /* # of matches against negative entry */
  73         long            cc_newloads;    /* # of successful loads of new entry */
  74
  75         /*
  76          * cc_searches - (cc_hits + cc_neg_hits + cc_newloads) is number of failed
  77          * searches, each of which will result in loading a negative entry
  78          */
  79         long            cc_invals;              /* # of entries invalidated from cache */
  80         long            cc_lsearches;   /* total # list-searches */
  81         long            cc_lhits;               /* # of matches against existing lists */
  82 #endif
  83 } CatCache;
  84
  85
  86 typedef struct catctup
  87 {
  88         int                     ct_magic;               /* for identifying CatCTup entries */
  89 #define CT_MAGIC   0x57261502
  90
  91         uint32          hash_value;             /* hash value for this tuple's keys */
  92
  93         /*
  94          * Lookup keys for the entry. By-reference datums point into the tuple for
  95          * positive cache entries, and are separately allocated for negative ones.
  96          */
  97         Datum           keys[CATCACHE_MAXKEYS];
  98
  99         /*
 100          * Each tuple in a cache is a member of a dlist that stores the elements
 101          * of its hash bucket.  We keep each dlist in LRU order to speed repeated
 102          * lookups.
 103          */
 104         dlist_node      cache_elem;             /* list member of per-bucket list */
 105
 106         /*
 107          * A tuple marked "dead" must not be returned by subsequent searches.
 108          * However, it won't be physically deleted from the cache until its
 109          * refcount goes to zero.  (If it's a member of a CatCList, the list's
 110          * refcount must go to zero, too; also, remember to mark the list dead at
 111          * the same time the tuple is marked.)
 112          *
 113          * A negative cache entry is an assertion that there is no tuple matching
 114          * a particular key.  This is just as useful as a normal entry so far as
 115          * avoiding catalog searches is concerned.  Management of positive and
 116          * negative entries is identical.
 117          */
 118         int                     refcount;               /* number of active references */
 119         bool            dead;                   /* dead but not yet removed? */
 120         bool            negative;               /* negative cache entry? */
 121         HeapTupleData tuple;            /* tuple management header */
 122
 123         /*
 124          * The tuple may also be a member of at most one CatCList.  (If a single
 125          * catcache is list-searched with varying numbers of keys, we may have to
 126          * make multiple entries for the same tuple because of this restriction.
 127          * Currently, that's not expected to be common, so we accept the potential
 128          * inefficiency.)
 129          */
 130         struct catclist *c_list;        /* containing CatCList, or NULL if none */
 131
 132         CatCache   *my_cache;           /* link to owning catcache */
 133         /* properly aligned tuple data follows, unless a negative entry */
 134 } CatCTup;
 135
 136
 137 /*
 138  * A CatCList describes the result of a partial search, ie, a search using
 139  * only the first K key columns of an N-key cache.  We store the keys used
 140  * into the keys attribute to represent the stored key set.  The CatCList
 141  * object contains links to cache entries for all the table rows satisfying
 142  * the partial key.  (Note: none of these will be negative cache entries.)
 143  *
 144  * A CatCList is only a member of a per-cache list; we do not currently
 145  * divide them into hash buckets.
 146  *
 147  * A list marked "dead" must not be returned by subsequent searches.
 148  * However, it won't be physically deleted from the cache until its
 149  * refcount goes to zero.  (A list should be marked dead if any of its
 150  * member entries are dead.)
 151  *
 152  * If "ordered" is true then the member tuples appear in the order of the
 153  * cache's underlying index.  This will be true in normal operation, but
 154  * might not be true during bootstrap or recovery operations. (namespace.c
 155  * is able to save some cycles when it is true.)
 156  */
 157 typedef struct catclist
 158 {
 159         int                     cl_magic;               /* for identifying CatCList entries */
 160 #define CL_MAGIC   0x52765103
 161
 162         uint32          hash_value;             /* hash value for lookup keys */
 163
 164         dlist_node      cache_elem;             /* list member of per-catcache list */
 165
 166         /*
 167          * Lookup keys for the entry, with the first nkeys elements being valid.
 168          * All by-reference are separately allocated.
 169          */
 170         Datum           keys[CATCACHE_MAXKEYS];
 171
 172         int                     refcount;               /* number of active references */
 173         bool            dead;                   /* dead but not yet removed? */
 174         bool            ordered;                /* members listed in index order? */
 175         short           nkeys;                  /* number of lookup keys specified */
 176         int                     n_members;              /* number of member tuples */
 177         CatCache   *my_cache;           /* link to owning catcache */
 178         CatCTup    *members[FLEXIBLE_ARRAY_MEMBER]; /* members */
 179 } CatCList;
 180
 181
 182 typedef struct catcacheheader
 183 {
 184         slist_head      ch_caches;              /* head of list of CatCache structs */
 185         int                     ch_ntup;                /* # of tuples in all caches */
 186 } CatCacheHeader;
 187
 188
 189 /* this extern duplicates utils/memutils.h... */
 190 extern PGDLLIMPORT MemoryContext CacheMemoryContext;
 191
 192 extern void CreateCacheMemoryContext(void);
 193
 194 extern CatCache *InitCatCache(int id, Oid reloid, Oid indexoid,
 195                                                           int nkeys, const int *key,
 196                                                           int nbuckets);
 197 extern void InitCatCachePhase2(CatCache *cache, bool touch_index);
 198
 199 extern HeapTuple SearchCatCache(CatCache *cache,
 200                                                                 Datum v1, Datum v2, Datum v3, Datum v4);
 201 extern HeapTuple SearchCatCache1(CatCache *cache,
 202                                                                  Datum v1);
 203 extern HeapTuple SearchCatCache2(CatCache *cache,
 204                                                                  Datum v1, Datum v2);
 205 extern HeapTuple SearchCatCache3(CatCache *cache,
 206                                                                  Datum v1, Datum v2, Datum v3);
 207 extern HeapTuple SearchCatCache4(CatCache *cache,
 208                                                                  Datum v1, Datum v2, Datum v3, Datum v4);
 209 extern void ReleaseCatCache(HeapTuple tuple);
 210
 211 extern uint32 GetCatCacheHashValue(CatCache *cache,
 212                                                                    Datum v1, Datum v2,
 213                                                                    Datum v3, Datum v4);
 214
 215 extern CatCList *SearchCatCacheList(CatCache *cache, int nkeys,
 216                                                                         Datum v1, Datum v2,
 217                                                                         Datum v3);
 218 extern void ReleaseCatCacheList(CatCList *list);
 219
 220 extern void ResetCatalogCaches(void);
 221 extern void CatalogCacheFlushCatalog(Oid catId);
 222 extern void CatCacheInvalidate(CatCache *cache, uint32 hashValue);
 223 extern void PrepareToInvalidateCacheTuple(Relation relation,
 224                                                                                   HeapTuple tuple,
 225                                                                                   HeapTuple newtuple,
 226                                                                                   void (*function) (int, uint32, Oid));
 227
 228 extern void PrintCatCacheLeakWarning(HeapTuple tuple);
 229 extern void PrintCatCacheListLeakWarning(CatCList *list);
 230
 231 #endif                                                  /* CATCACHE_H */