granicus.if.org Git - postgresql/blob - src/backend/catalog/pg_largeobject.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * pg_largeobject.c
   4  *        routines to support manipulation of the pg_largeobject relation
   5  *
   6  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        $PostgreSQL: pgsql/src/backend/catalog/pg_largeobject.c,v 1.27 2007/01/05 22:19:25 momjian Exp $
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 #include "postgres.h"
  16
  17 #include "access/genam.h"
  18 #include "access/heapam.h"
  19 #include "catalog/indexing.h"
  20 #include "catalog/pg_largeobject.h"
  21 #include "utils/builtins.h"
  22 #include "utils/fmgroids.h"
  23
  24
  25 /*
  26  * Create a large object having the given LO identifier.
  27  *
  28  * We do this by inserting an empty first page, so that the object will
  29  * appear to exist with size 0.  Note that the unique index will reject
  30  * an attempt to create a duplicate page.
  31  */
  32 void
  33 LargeObjectCreate(Oid loid)
  34 {
  35         Relation        pg_largeobject;
  36         HeapTuple       ntup;
  37         Datum           values[Natts_pg_largeobject];
  38         char            nulls[Natts_pg_largeobject];
  39         int                     i;
  40
  41         pg_largeobject = heap_open(LargeObjectRelationId, RowExclusiveLock);
  42
  43         /*
  44          * Form new tuple
  45          */
  46         for (i = 0; i < Natts_pg_largeobject; i++)
  47         {
  48                 values[i] = (Datum) NULL;
  49                 nulls[i] = ' ';
  50         }
  51
  52         i = 0;
  53         values[i++] = ObjectIdGetDatum(loid);
  54         values[i++] = Int32GetDatum(0);
  55         values[i++] = DirectFunctionCall1(byteain,
  56                                                                           CStringGetDatum(""));
  57
  58         ntup = heap_formtuple(pg_largeobject->rd_att, values, nulls);
  59
  60         /*
  61          * Insert it
  62          */
  63         simple_heap_insert(pg_largeobject, ntup);
  64
  65         /* Update indexes */
  66         CatalogUpdateIndexes(pg_largeobject, ntup);
  67
  68         heap_close(pg_largeobject, RowExclusiveLock);
  69
  70         heap_freetuple(ntup);
  71 }
  72
  73 void
  74 LargeObjectDrop(Oid loid)
  75 {
  76         bool            found = false;
  77         Relation        pg_largeobject;
  78         ScanKeyData skey[1];
  79         SysScanDesc sd;
  80         HeapTuple       tuple;
  81
  82         ScanKeyInit(&skey[0],
  83                                 Anum_pg_largeobject_loid,
  84                                 BTEqualStrategyNumber, F_OIDEQ,
  85                                 ObjectIdGetDatum(loid));
  86
  87         pg_largeobject = heap_open(LargeObjectRelationId, RowExclusiveLock);
  88
  89         sd = systable_beginscan(pg_largeobject, LargeObjectLOidPNIndexId, true,
  90                                                         SnapshotNow, 1, skey);
  91
  92         while ((tuple = systable_getnext(sd)) != NULL)
  93         {
  94                 simple_heap_delete(pg_largeobject, &tuple->t_self);
  95                 found = true;
  96         }
  97
  98         systable_endscan(sd);
  99
 100         heap_close(pg_largeobject, RowExclusiveLock);
 101
 102         if (!found)
 103                 ereport(ERROR,
 104                                 (errcode(ERRCODE_UNDEFINED_OBJECT),
 105                                  errmsg("large object %u does not exist", loid)));
 106 }
 107
 108 bool
 109 LargeObjectExists(Oid loid)
 110 {
 111         bool            retval = false;
 112         Relation        pg_largeobject;
 113         ScanKeyData skey[1];
 114         SysScanDesc sd;
 115
 116         /*
 117          * See if we can find any tuples belonging to the specified LO
 118          */
 119         ScanKeyInit(&skey[0],
 120                                 Anum_pg_largeobject_loid,
 121                                 BTEqualStrategyNumber, F_OIDEQ,
 122                                 ObjectIdGetDatum(loid));
 123
 124         pg_largeobject = heap_open(LargeObjectRelationId, AccessShareLock);
 125
 126         sd = systable_beginscan(pg_largeobject, LargeObjectLOidPNIndexId, true,
 127                                                         SnapshotNow, 1, skey);
 128
 129         if (systable_getnext(sd) != NULL)
 130                 retval = true;
 131
 132         systable_endscan(sd);
 133
 134         heap_close(pg_largeobject, AccessShareLock);
 135
 136         return retval;
 137 }