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) 1996-2002, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        $Header: /cvsroot/pgsql/src/backend/catalog/pg_largeobject.c,v 1.15 2003/07/21 01:59:10 tgl Exp $
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 #include "postgres.h"
  16
  17 #include "access/genam.h"
  18 #include "access/heapam.h"
  19 #include "catalog/catname.h"
  20 #include "catalog/indexing.h"
  21 #include "catalog/pg_largeobject.h"
  22 #include "miscadmin.h"
  23 #include "utils/builtins.h"
  24 #include "utils/fmgroids.h"
  25
  26
  27 /*
  28  * Create a large object having the given LO identifier.
  29  *
  30  * We do this by inserting an empty first page, so that the object will
  31  * appear to exist with size 0.  Note that the unique index will reject
  32  * an attempt to create a duplicate page.
  33  */
  34 void
  35 LargeObjectCreate(Oid loid)
  36 {
  37         Relation        pg_largeobject;
  38         HeapTuple       ntup;
  39         Datum           values[Natts_pg_largeobject];
  40         char            nulls[Natts_pg_largeobject];
  41         int                     i;
  42
  43         pg_largeobject = heap_openr(LargeObjectRelationName, RowExclusiveLock);
  44
  45         /*
  46          * Form new tuple
  47          */
  48         for (i = 0; i < Natts_pg_largeobject; i++)
  49         {
  50                 values[i] = (Datum) NULL;
  51                 nulls[i] = ' ';
  52         }
  53
  54         i = 0;
  55         values[i++] = ObjectIdGetDatum(loid);
  56         values[i++] = Int32GetDatum(0);
  57         values[i++] = DirectFunctionCall1(byteain,
  58                                                                           CStringGetDatum(""));
  59
  60         ntup = heap_formtuple(pg_largeobject->rd_att, values, nulls);
  61
  62         /*
  63          * Insert it
  64          */
  65         simple_heap_insert(pg_largeobject, ntup);
  66
  67         /* Update indexes */
  68         CatalogUpdateIndexes(pg_largeobject, ntup);
  69
  70         heap_close(pg_largeobject, RowExclusiveLock);
  71
  72         heap_freetuple(ntup);
  73 }
  74
  75 void
  76 LargeObjectDrop(Oid loid)
  77 {
  78         bool            found = false;
  79         Relation        pg_largeobject;
  80         Relation        pg_lo_idx;
  81         ScanKeyData skey[1];
  82         IndexScanDesc sd;
  83         HeapTuple       tuple;
  84
  85         ScanKeyEntryInitialize(&skey[0],
  86                                                    (bits16) 0x0,
  87                                                    (AttrNumber) 1,
  88                                                    (RegProcedure) F_OIDEQ,
  89                                                    ObjectIdGetDatum(loid));
  90
  91         pg_largeobject = heap_openr(LargeObjectRelationName, RowShareLock);
  92         pg_lo_idx = index_openr(LargeObjectLOidPNIndex);
  93
  94         sd = index_beginscan(pg_largeobject, pg_lo_idx, SnapshotNow, 1, skey);
  95
  96         while ((tuple = index_getnext(sd, ForwardScanDirection)) != NULL)
  97         {
  98                 simple_heap_delete(pg_largeobject, &tuple->t_self);
  99                 found = true;
 100         }
 101
 102         index_endscan(sd);
 103
 104         index_close(pg_lo_idx);
 105         heap_close(pg_largeobject, RowShareLock);
 106
 107         if (!found)
 108                 ereport(ERROR,
 109                                 (errcode(ERRCODE_UNDEFINED_OBJECT),
 110                                  errmsg("large object %u does not exist", loid)));
 111 }
 112
 113 bool
 114 LargeObjectExists(Oid loid)
 115 {
 116         bool            retval = false;
 117         Relation        pg_largeobject;
 118         Relation        pg_lo_idx;
 119         ScanKeyData skey[1];
 120         IndexScanDesc sd;
 121         HeapTuple       tuple;
 122
 123         /*
 124          * See if we can find any tuples belonging to the specified LO
 125          */
 126         ScanKeyEntryInitialize(&skey[0],
 127                                                    (bits16) 0x0,
 128                                                    (AttrNumber) 1,
 129                                                    (RegProcedure) F_OIDEQ,
 130                                                    ObjectIdGetDatum(loid));
 131
 132         pg_largeobject = heap_openr(LargeObjectRelationName, RowShareLock);
 133         pg_lo_idx = index_openr(LargeObjectLOidPNIndex);
 134
 135         sd = index_beginscan(pg_largeobject, pg_lo_idx, SnapshotNow, 1, skey);
 136
 137         if ((tuple = index_getnext(sd, ForwardScanDirection)) != NULL)
 138                 retval = true;
 139
 140         index_endscan(sd);
 141
 142         index_close(pg_lo_idx);
 143         heap_close(pg_largeobject, RowShareLock);
 144
 145         return retval;
 146 }