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) 1996-2006, 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 1.25 2006/03/05 15:58:23 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 "miscadmin.h"
  22 #include "utils/builtins.h"
  23 #include "utils/fmgroids.h"
  24
  25
  26 /*
  27  * Create a large object having the given LO identifier.
  28  *
  29  * We do this by inserting an empty first page, so that the object will
  30  * appear to exist with size 0.  Note that the unique index will reject
  31  * an attempt to create a duplicate page.
  32  */
  33 void
  34 LargeObjectCreate(Oid loid)
  35 {
  36         Relation        pg_largeobject;
  37         HeapTuple       ntup;
  38         Datum           values[Natts_pg_largeobject];
  39         char            nulls[Natts_pg_largeobject];
  40         int                     i;
  41
  42         pg_largeobject = heap_open(LargeObjectRelationId, RowExclusiveLock);
  43
  44         /*
  45          * Form new tuple
  46          */
  47         for (i = 0; i < Natts_pg_largeobject; i++)
  48         {
  49                 values[i] = (Datum) NULL;
  50                 nulls[i] = ' ';
  51         }
  52
  53         i = 0;
  54         values[i++] = ObjectIdGetDatum(loid);
  55         values[i++] = Int32GetDatum(0);
  56         values[i++] = DirectFunctionCall1(byteain,
  57                                                                           CStringGetDatum(""));
  58
  59         ntup = heap_formtuple(pg_largeobject->rd_att, values, nulls);
  60
  61         /*
  62          * Insert it
  63          */
  64         simple_heap_insert(pg_largeobject, ntup);
  65
  66         /* Update indexes */
  67         CatalogUpdateIndexes(pg_largeobject, ntup);
  68
  69         heap_close(pg_largeobject, RowExclusiveLock);
  70
  71         heap_freetuple(ntup);
  72 }
  73
  74 void
  75 LargeObjectDrop(Oid loid)
  76 {
  77         bool            found = false;
  78         Relation        pg_largeobject;
  79         ScanKeyData skey[1];
  80         SysScanDesc sd;
  81         HeapTuple       tuple;
  82
  83         ScanKeyInit(&skey[0],
  84                                 Anum_pg_largeobject_loid,
  85                                 BTEqualStrategyNumber, F_OIDEQ,
  86                                 ObjectIdGetDatum(loid));
  87
  88         pg_largeobject = heap_open(LargeObjectRelationId, RowExclusiveLock);
  89
  90         sd = systable_beginscan(pg_largeobject, LargeObjectLOidPNIndexId, true,
  91                                                         SnapshotNow, 1, skey);
  92
  93         while ((tuple = systable_getnext(sd)) != NULL)
  94         {
  95                 simple_heap_delete(pg_largeobject, &tuple->t_self);
  96                 found = true;
  97         }
  98
  99         systable_endscan(sd);
 100
 101         heap_close(pg_largeobject, RowExclusiveLock);
 102
 103         if (!found)
 104                 ereport(ERROR,
 105                                 (errcode(ERRCODE_UNDEFINED_OBJECT),
 106                                  errmsg("large object %u does not exist", loid)));
 107 }
 108
 109 bool
 110 LargeObjectExists(Oid loid)
 111 {
 112         bool            retval = false;
 113         Relation        pg_largeobject;
 114         ScanKeyData skey[1];
 115         SysScanDesc sd;
 116
 117         /*
 118          * See if we can find any tuples belonging to the specified LO
 119          */
 120         ScanKeyInit(&skey[0],
 121                                 Anum_pg_largeobject_loid,
 122                                 BTEqualStrategyNumber, F_OIDEQ,
 123                                 ObjectIdGetDatum(loid));
 124
 125         pg_largeobject = heap_open(LargeObjectRelationId, AccessShareLock);
 126
 127         sd = systable_beginscan(pg_largeobject, LargeObjectLOidPNIndexId, true,
 128                                                         SnapshotNow, 1, skey);
 129
 130         if (systable_getnext(sd) != NULL)
 131                 retval = true;
 132
 133         systable_endscan(sd);
 134
 135         heap_close(pg_largeobject, AccessShareLock);
 136
 137         return retval;
 138 }