src/backend/utils/cache/typcache.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * typcache.c
   4  *        POSTGRES type cache code
   5  *
   6  * The type cache exists to speed lookup of certain information about data
   7  * types that is not directly available from a type's pg_type row.  In
   8  * particular, we use a type's default btree opclass, or the default hash
   9  * opclass if no btree opclass exists, to determine which operators should
  10  * be used for grouping and sorting the type (GROUP BY, ORDER BY ASC/DESC).
  11  *
  12  * Several seemingly-odd choices have been made to support use of the type
  13  * cache by the generic array comparison routines array_eq() and array_cmp().
  14  * Because these routines are used as index support operations, they cannot
  15  * leak memory.  To allow them to execute efficiently, all information that
  16  * either of them would like to re-use across calls is made available in the
  17  * type cache.
  18  *
  19  * Once created, a type cache entry lives as long as the backend does, so
  20  * there is no need for a call to release a cache entry.  (For present uses,
  21  * it would be okay to flush type cache entries at the ends of transactions,
  22  * if we needed to reclaim space.)
  23  *
  24  * There is presently no provision for clearing out a cache entry if the
  25  * stored data becomes obsolete.  (The code will work if a type acquires
  26  * opclasses it didn't have before while a backend runs --- but not if the
  27  * definition of an existing opclass is altered.)  However, the relcache
  28  * doesn't cope with opclasses changing under it, either, so this seems
  29  * a low-priority problem.
  30  *
  31  * We do support clearing the tuple descriptor part of a rowtype's cache
  32  * entry, since that may need to change as a consequence of ALTER TABLE.
  33  *
  34  *
  35  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  36  * Portions Copyright (c) 1994, Regents of the University of California
  37  *
  38  * IDENTIFICATION
  39  *        $PostgreSQL: pgsql/src/backend/utils/cache/typcache.c,v 1.21 2006/07/14 14:52:25 momjian Exp $
  40  *
  41  *-------------------------------------------------------------------------
  42  */
  43 #include "postgres.h"
  44
  45 #include "access/hash.h"
  46 #include "access/heapam.h"
  47 #include "access/nbtree.h"
  48 #include "catalog/pg_type.h"
  49 #include "commands/defrem.h"
  50 #include "utils/builtins.h"
  51 #include "utils/lsyscache.h"
  52 #include "utils/syscache.h"
  53 #include "utils/typcache.h"
  54
  55
  56 /* The main type cache hashtable searched by lookup_type_cache */
  57 static HTAB *TypeCacheHash = NULL;
  58
  59 /*
  60  * We use a separate table for storing the definitions of non-anonymous
  61  * record types.  Once defined, a record type will be remembered for the
  62  * life of the backend.  Subsequent uses of the "same" record type (where
  63  * sameness means equalTupleDescs) will refer to the existing table entry.
  64  *
  65  * Stored record types are remembered in a linear array of TupleDescs,
  66  * which can be indexed quickly with the assigned typmod.  There is also
  67  * a hash table to speed searches for matching TupleDescs.      The hash key
  68  * uses just the first N columns' type OIDs, and so we may have multiple
  69  * entries with the same hash key.
  70  */
  71 #define REC_HASH_KEYS   16              /* use this many columns in hash key */
  72
  73 typedef struct RecordCacheEntry
  74 {
  75         /* the hash lookup key MUST BE FIRST */
  76         Oid                     hashkey[REC_HASH_KEYS]; /* column type IDs, zero-filled */
  77
  78         /* list of TupleDescs for record types with this hashkey */
  79         List       *tupdescs;
  80 } RecordCacheEntry;
  81
  82 static HTAB *RecordCacheHash = NULL;
  83
  84 static TupleDesc *RecordCacheArray = NULL;
  85 static int32 RecordCacheArrayLen = 0;   /* allocated length of array */
  86 static int32 NextRecordTypmod = 0;              /* number of entries used */
  87
  88
  89 /*
  90  * lookup_type_cache
  91  *
  92  * Fetch the type cache entry for the specified datatype, and make sure that
  93  * all the fields requested by bits in 'flags' are valid.
  94  *
  95  * The result is never NULL --- we will elog() if the passed type OID is
  96  * invalid.  Note however that we may fail to find one or more of the
  97  * requested opclass-dependent fields; the caller needs to check whether
  98  * the fields are InvalidOid or not.
  99  */
 100 TypeCacheEntry *
 101 lookup_type_cache(Oid type_id, int flags)
 102 {
 103         TypeCacheEntry *typentry;
 104         bool            found;
 105
 106         if (TypeCacheHash == NULL)
 107         {
 108                 /* First time through: initialize the hash table */
 109                 HASHCTL         ctl;
 110
 111                 if (!CacheMemoryContext)
 112                         CreateCacheMemoryContext();
 113
 114                 MemSet(&ctl, 0, sizeof(ctl));
 115                 ctl.keysize = sizeof(Oid);
 116                 ctl.entrysize = sizeof(TypeCacheEntry);
 117                 ctl.hash = oid_hash;
 118                 TypeCacheHash = hash_create("Type information cache", 64,
 119                                                                         &ctl, HASH_ELEM | HASH_FUNCTION);
 120         }
 121
 122         /* Try to look up an existing entry */
 123         typentry = (TypeCacheEntry *) hash_search(TypeCacheHash,
 124                                                                                           (void *) &type_id,
 125                                                                                           HASH_FIND, NULL);
 126         if (typentry == NULL)
 127         {
 128                 /*
 129                  * If we didn't find one, we want to make one.  But first look up the
 130                  * pg_type row, just to make sure we don't make a cache entry for an
 131                  * invalid type OID.
 132                  */
 133                 HeapTuple       tp;
 134                 Form_pg_type typtup;
 135
 136                 tp = SearchSysCache(TYPEOID,
 137                                                         ObjectIdGetDatum(type_id),
 138                                                         0, 0, 0);
 139                 if (!HeapTupleIsValid(tp))
 140                         elog(ERROR, "cache lookup failed for type %u", type_id);
 141                 typtup = (Form_pg_type) GETSTRUCT(tp);
 142                 if (!typtup->typisdefined)
 143                         ereport(ERROR,
 144                                         (errcode(ERRCODE_UNDEFINED_OBJECT),
 145                                          errmsg("type \"%s\" is only a shell",
 146                                                         NameStr(typtup->typname))));
 147
 148                 /* Now make the typcache entry */
 149                 typentry = (TypeCacheEntry *) hash_search(TypeCacheHash,
 150                                                                                                   (void *) &type_id,
 151                                                                                                   HASH_ENTER, &found);
 152                 Assert(!found);                 /* it wasn't there a moment ago */
 153
 154                 MemSet(typentry, 0, sizeof(TypeCacheEntry));
 155                 typentry->type_id = type_id;
 156                 typentry->typlen = typtup->typlen;
 157                 typentry->typbyval = typtup->typbyval;
 158                 typentry->typalign = typtup->typalign;
 159                 typentry->typtype = typtup->typtype;
 160                 typentry->typrelid = typtup->typrelid;
 161
 162                 ReleaseSysCache(tp);
 163         }
 164
 165         /* If we haven't already found the opclass, try to do so */
 166         if ((flags & (TYPECACHE_EQ_OPR | TYPECACHE_LT_OPR | TYPECACHE_GT_OPR |
 167                                   TYPECACHE_CMP_PROC |
 168                                   TYPECACHE_EQ_OPR_FINFO | TYPECACHE_CMP_PROC_FINFO)) &&
 169                 typentry->btree_opc == InvalidOid)
 170         {
 171                 typentry->btree_opc = GetDefaultOpClass(type_id,
 172                                                                                                 BTREE_AM_OID);
 173                 /* Only care about hash opclass if no btree opclass... */
 174                 if (typentry->btree_opc == InvalidOid)
 175                 {
 176                         if (typentry->hash_opc == InvalidOid)
 177                                 typentry->hash_opc = GetDefaultOpClass(type_id,
 178                                                                                                            HASH_AM_OID);
 179                 }
 180                 else
 181                 {
 182                         /*
 183                          * If we find a btree opclass where previously we only found a
 184                          * hash opclass, forget the hash equality operator so we can use
 185                          * the btree operator instead.
 186                          */
 187                         typentry->eq_opr = InvalidOid;
 188                         typentry->eq_opr_finfo.fn_oid = InvalidOid;
 189                 }
 190         }
 191
 192         /* Look for requested operators and functions */
 193         if ((flags & (TYPECACHE_EQ_OPR | TYPECACHE_EQ_OPR_FINFO)) &&
 194                 typentry->eq_opr == InvalidOid)
 195         {
 196                 if (typentry->btree_opc != InvalidOid)
 197                         typentry->eq_opr = get_opclass_member(typentry->btree_opc,
 198                                                                                                   InvalidOid,
 199                                                                                                   BTEqualStrategyNumber);
 200                 if (typentry->eq_opr == InvalidOid &&
 201                         typentry->hash_opc != InvalidOid)
 202                         typentry->eq_opr = get_opclass_member(typentry->hash_opc,
 203                                                                                                   InvalidOid,
 204                                                                                                   HTEqualStrategyNumber);
 205         }
 206         if ((flags & TYPECACHE_LT_OPR) && typentry->lt_opr == InvalidOid)
 207         {
 208                 if (typentry->btree_opc != InvalidOid)
 209                         typentry->lt_opr = get_opclass_member(typentry->btree_opc,
 210                                                                                                   InvalidOid,
 211                                                                                                   BTLessStrategyNumber);
 212         }
 213         if ((flags & TYPECACHE_GT_OPR) && typentry->gt_opr == InvalidOid)
 214         {
 215                 if (typentry->btree_opc != InvalidOid)
 216                         typentry->gt_opr = get_opclass_member(typentry->btree_opc,
 217                                                                                                   InvalidOid,
 218                                                                                                   BTGreaterStrategyNumber);
 219         }
 220         if ((flags & (TYPECACHE_CMP_PROC | TYPECACHE_CMP_PROC_FINFO)) &&
 221                 typentry->cmp_proc == InvalidOid)
 222         {
 223                 if (typentry->btree_opc != InvalidOid)
 224                         typentry->cmp_proc = get_opclass_proc(typentry->btree_opc,
 225                                                                                                   InvalidOid,
 226                                                                                                   BTORDER_PROC);
 227         }
 228
 229         /*
 230          * Set up fmgr lookup info as requested
 231          *
 232          * Note: we tell fmgr the finfo structures live in CacheMemoryContext,
 233          * which is not quite right (they're really in DynaHashContext) but this
 234          * will do for our purposes.
 235          */
 236         if ((flags & TYPECACHE_EQ_OPR_FINFO) &&
 237                 typentry->eq_opr_finfo.fn_oid == InvalidOid &&
 238                 typentry->eq_opr != InvalidOid)
 239         {
 240                 Oid                     eq_opr_func;
 241
 242                 eq_opr_func = get_opcode(typentry->eq_opr);
 243                 if (eq_opr_func != InvalidOid)
 244                         fmgr_info_cxt(eq_opr_func, &typentry->eq_opr_finfo,
 245                                                   CacheMemoryContext);
 246         }
 247         if ((flags & TYPECACHE_CMP_PROC_FINFO) &&
 248                 typentry->cmp_proc_finfo.fn_oid == InvalidOid &&
 249                 typentry->cmp_proc != InvalidOid)
 250         {
 251                 fmgr_info_cxt(typentry->cmp_proc, &typentry->cmp_proc_finfo,
 252                                           CacheMemoryContext);
 253         }
 254
 255         /*
 256          * If it's a composite type (row type), get tupdesc if requested
 257          */
 258         if ((flags & TYPECACHE_TUPDESC) &&
 259                 typentry->tupDesc == NULL &&
 260                 typentry->typtype == 'c')
 261         {
 262                 Relation        rel;
 263
 264                 if (!OidIsValid(typentry->typrelid))    /* should not happen */
 265                         elog(ERROR, "invalid typrelid for composite type %u",
 266                                  typentry->type_id);
 267                 rel = relation_open(typentry->typrelid, AccessShareLock);
 268                 Assert(rel->rd_rel->reltype == typentry->type_id);
 269
 270                 /*
 271                  * Link to the tupdesc and increment its refcount (we assert it's
 272                  * a refcounted descriptor).  We don't use IncrTupleDescRefCount()
 273                  * for this, because the reference mustn't be entered in the current
 274                  * resource owner; it can outlive the current query.
 275                  */
 276                 typentry->tupDesc = RelationGetDescr(rel);
 277
 278                 Assert(typentry->tupDesc->tdrefcount > 0);
 279                 typentry->tupDesc->tdrefcount++;
 280
 281                 relation_close(rel, AccessShareLock);
 282         }
 283
 284         return typentry;
 285 }
 286
 287 /*
 288  * lookup_rowtype_tupdesc_internal --- internal routine to lookup a rowtype
 289  *
 290  * Same API as lookup_rowtype_tupdesc_noerror, but the returned tupdesc
 291  * hasn't had its refcount bumped.
 292  */
 293 static TupleDesc
 294 lookup_rowtype_tupdesc_internal(Oid type_id, int32 typmod, bool noError)
 295 {
 296         if (type_id != RECORDOID)
 297         {
 298                 /*
 299                  * It's a named composite type, so use the regular typcache.
 300                  */
 301                 TypeCacheEntry *typentry;
 302
 303                 typentry = lookup_type_cache(type_id, TYPECACHE_TUPDESC);
 304                 if (typentry->tupDesc == NULL && !noError)
 305                         ereport(ERROR,
 306                                         (errcode(ERRCODE_WRONG_OBJECT_TYPE),
 307                                          errmsg("type %s is not composite",
 308                                                         format_type_be(type_id))));
 309                 return typentry->tupDesc;
 310         }
 311         else
 312         {
 313                 /*
 314                  * It's a transient record type, so look in our record-type table.
 315                  */
 316                 if (typmod < 0 || typmod >= NextRecordTypmod)
 317                 {
 318                         if (!noError)
 319                                 ereport(ERROR,
 320                                                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
 321                                                  errmsg("record type has not been registered")));
 322                         return NULL;
 323                 }
 324                 return RecordCacheArray[typmod];
 325         }
 326 }
 327
 328 /*
 329  * lookup_rowtype_tupdesc
 330  *
 331  * Given a typeid/typmod that should describe a known composite type,
 332  * return the tuple descriptor for the type.  Will ereport on failure.
 333  *
 334  * Note: on success, we increment the refcount of the returned TupleDesc,
 335  * and log the reference in CurrentResourceOwner.  Caller should call
 336  * ReleaseTupleDesc or DecrTupleDescRefCount when done using the tupdesc.
 337  */
 338 TupleDesc
 339 lookup_rowtype_tupdesc(Oid type_id, int32 typmod)
 340 {
 341         TupleDesc       tupDesc;
 342
 343         tupDesc = lookup_rowtype_tupdesc_internal(type_id, typmod, false);
 344         IncrTupleDescRefCount(tupDesc);
 345         return tupDesc;
 346 }
 347
 348 /*
 349  * lookup_rowtype_tupdesc_noerror
 350  *
 351  * As above, but if the type is not a known composite type and noError
 352  * is true, returns NULL instead of ereport'ing.  (Note that if a bogus
 353  * type_id is passed, you'll get an ereport anyway.)
 354  */
 355 TupleDesc
 356 lookup_rowtype_tupdesc_noerror(Oid type_id, int32 typmod, bool noError)
 357 {
 358         TupleDesc       tupDesc;
 359
 360         tupDesc = lookup_rowtype_tupdesc_internal(type_id, typmod, noError);
 361         if (tupDesc != NULL)
 362                 IncrTupleDescRefCount(tupDesc);
 363         return tupDesc;
 364 }
 365
 366 /*
 367  * lookup_rowtype_tupdesc_copy
 368  *
 369  * Like lookup_rowtype_tupdesc(), but the returned TupleDesc has been
 370  * copied into the CurrentMemoryContext and is not reference-counted.
 371  */
 372 TupleDesc
 373 lookup_rowtype_tupdesc_copy(Oid type_id, int32 typmod)
 374 {
 375         TupleDesc tmp;
 376
 377         tmp = lookup_rowtype_tupdesc_internal(type_id, typmod, false);
 378         return CreateTupleDescCopyConstr(tmp);
 379 }
 380
 381
 382 /*
 383  * assign_record_type_typmod
 384  *
 385  * Given a tuple descriptor for a RECORD type, find or create a cache entry
 386  * for the type, and set the tupdesc's tdtypmod field to a value that will
 387  * identify this cache entry to lookup_rowtype_tupdesc.
 388  */
 389 void
 390 assign_record_type_typmod(TupleDesc tupDesc)
 391 {
 392         RecordCacheEntry *recentry;
 393         TupleDesc       entDesc;
 394         Oid                     hashkey[REC_HASH_KEYS];
 395         bool            found;
 396         int                     i;
 397         ListCell   *l;
 398         int32           newtypmod;
 399         MemoryContext oldcxt;
 400
 401         Assert(tupDesc->tdtypeid == RECORDOID);
 402
 403         if (RecordCacheHash == NULL)
 404         {
 405                 /* First time through: initialize the hash table */
 406                 HASHCTL         ctl;
 407
 408                 if (!CacheMemoryContext)
 409                         CreateCacheMemoryContext();
 410
 411                 MemSet(&ctl, 0, sizeof(ctl));
 412                 ctl.keysize = REC_HASH_KEYS * sizeof(Oid);
 413                 ctl.entrysize = sizeof(RecordCacheEntry);
 414                 ctl.hash = tag_hash;
 415                 RecordCacheHash = hash_create("Record information cache", 64,
 416                                                                           &ctl, HASH_ELEM | HASH_FUNCTION);
 417         }
 418
 419         /* Find or create a hashtable entry for this hash class */
 420         MemSet(hashkey, 0, sizeof(hashkey));
 421         for (i = 0; i < tupDesc->natts; i++)
 422         {
 423                 if (i >= REC_HASH_KEYS)
 424                         break;
 425                 hashkey[i] = tupDesc->attrs[i]->atttypid;
 426         }
 427         recentry = (RecordCacheEntry *) hash_search(RecordCacheHash,
 428                                                                                                 (void *) hashkey,
 429                                                                                                 HASH_ENTER, &found);
 430         if (!found)
 431         {
 432                 /* New entry ... hash_search initialized only the hash key */
 433                 recentry->tupdescs = NIL;
 434         }
 435
 436         /* Look for existing record cache entry */
 437         foreach(l, recentry->tupdescs)
 438         {
 439                 entDesc = (TupleDesc) lfirst(l);
 440                 if (equalTupleDescs(tupDesc, entDesc))
 441                 {
 442                         tupDesc->tdtypmod = entDesc->tdtypmod;
 443                         return;
 444                 }
 445         }
 446
 447         /* Not present, so need to manufacture an entry */
 448         oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
 449
 450         if (RecordCacheArray == NULL)
 451         {
 452                 RecordCacheArray = (TupleDesc *) palloc(64 * sizeof(TupleDesc));
 453                 RecordCacheArrayLen = 64;
 454         }
 455         else if (NextRecordTypmod >= RecordCacheArrayLen)
 456         {
 457                 int32           newlen = RecordCacheArrayLen * 2;
 458
 459                 RecordCacheArray = (TupleDesc *) repalloc(RecordCacheArray,
 460                                                                                                   newlen * sizeof(TupleDesc));
 461                 RecordCacheArrayLen = newlen;
 462         }
 463
 464         /* if fail in subrs, no damage except possibly some wasted memory... */
 465         entDesc = CreateTupleDescCopy(tupDesc);
 466         recentry->tupdescs = lcons(entDesc, recentry->tupdescs);
 467         /* mark it as a reference-counted tupdesc */
 468         entDesc->tdrefcount = 1;
 469         /* now it's safe to advance NextRecordTypmod */
 470         newtypmod = NextRecordTypmod++;
 471         entDesc->tdtypmod = newtypmod;
 472         RecordCacheArray[newtypmod] = entDesc;
 473
 474         /* report to caller as well */
 475         tupDesc->tdtypmod = newtypmod;
 476
 477         MemoryContextSwitchTo(oldcxt);
 478 }
 479
 480 /*
 481  * flush_rowtype_cache
 482  *
 483  * If a typcache entry exists for a rowtype, delete the entry's cached
 484  * tuple descriptor link.  This is called from relcache.c when a cached
 485  * relation tupdesc is about to be dropped.
 486  */
 487 void
 488 flush_rowtype_cache(Oid type_id)
 489 {
 490         TypeCacheEntry *typentry;
 491
 492         if (TypeCacheHash == NULL)
 493                 return;                                 /* no table, so certainly no entry */
 494
 495         typentry = (TypeCacheEntry *) hash_search(TypeCacheHash,
 496                                                                                           (void *) &type_id,
 497                                                                                           HASH_FIND, NULL);
 498         if (typentry == NULL)
 499                 return;                                 /* no matching entry */
 500         if (typentry->tupDesc == NULL)
 501                 return;                                 /* tupdesc hasn't been requested */
 502
 503         /*
 504          * Release our refcount and free the tupdesc if none remain.
 505          * (Can't use DecrTupleDescRefCount because this reference is not
 506          * logged in current resource owner.)
 507          */
 508         Assert(typentry->tupDesc->tdrefcount > 0);
 509         if (--typentry->tupDesc->tdrefcount == 0)
 510                 FreeTupleDesc(typentry->tupDesc);
 511
 512         typentry->tupDesc = NULL;
 513 }