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) 1996-2001, 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 1.11 2002/05/20 23:51:42 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         Relation        idescs[Num_pg_largeobject_indices];
  40         Datum           values[Natts_pg_largeobject];
  41         char            nulls[Natts_pg_largeobject];
  42         int                     i;
  43
  44         pg_largeobject = heap_openr(LargeObjectRelationName, RowExclusiveLock);
  45
  46         /*
  47          * Form new tuple
  48          */
  49         for (i = 0; i < Natts_pg_largeobject; i++)
  50         {
  51                 values[i] = (Datum) NULL;
  52                 nulls[i] = ' ';
  53         }
  54
  55         i = 0;
  56         values[i++] = ObjectIdGetDatum(loid);
  57         values[i++] = Int32GetDatum(0);
  58         values[i++] = DirectFunctionCall1(byteain,
  59                                                                           CStringGetDatum(""));
  60
  61         ntup = heap_formtuple(pg_largeobject->rd_att, values, nulls);
  62
  63         /*
  64          * Insert it
  65          */
  66         heap_insert(pg_largeobject, ntup);
  67
  68         /*
  69          * Update indices
  70          */
  71         if (!IsIgnoringSystemIndexes())
  72         {
  73                 CatalogOpenIndices(Num_pg_largeobject_indices, Name_pg_largeobject_indices, idescs);
  74                 CatalogIndexInsert(idescs, Num_pg_largeobject_indices, pg_largeobject, ntup);
  75                 CatalogCloseIndices(Num_pg_largeobject_indices, idescs);
  76         }
  77
  78         heap_close(pg_largeobject, RowExclusiveLock);
  79
  80         heap_freetuple(ntup);
  81 }
  82
  83 void
  84 LargeObjectDrop(Oid loid)
  85 {
  86         bool            found = false;
  87         Relation        pg_largeobject;
  88         Relation        pg_lo_idx;
  89         ScanKeyData skey[1];
  90         IndexScanDesc sd;
  91         HeapTuple       tuple;
  92
  93         ScanKeyEntryInitialize(&skey[0],
  94                                                    (bits16) 0x0,
  95                                                    (AttrNumber) 1,
  96                                                    (RegProcedure) F_OIDEQ,
  97                                                    ObjectIdGetDatum(loid));
  98
  99         pg_largeobject = heap_openr(LargeObjectRelationName, RowShareLock);
 100         pg_lo_idx = index_openr(LargeObjectLOidPNIndex);
 101
 102         sd = index_beginscan(pg_largeobject, pg_lo_idx, SnapshotNow, 1, skey);
 103
 104         while ((tuple = index_getnext(sd, ForwardScanDirection)) != NULL)
 105         {
 106                 simple_heap_delete(pg_largeobject, &tuple->t_self);
 107                 found = true;
 108         }
 109
 110         index_endscan(sd);
 111
 112         index_close(pg_lo_idx);
 113         heap_close(pg_largeobject, RowShareLock);
 114
 115         if (!found)
 116                 elog(ERROR, "LargeObjectDrop: large object %u not found", loid);
 117 }
 118
 119 bool
 120 LargeObjectExists(Oid loid)
 121 {
 122         bool            retval = false;
 123         Relation        pg_largeobject;
 124         Relation        pg_lo_idx;
 125         ScanKeyData skey[1];
 126         IndexScanDesc sd;
 127         HeapTuple       tuple;
 128
 129         /*
 130          * See if we can find any tuples belonging to the specified LO
 131          */
 132         ScanKeyEntryInitialize(&skey[0],
 133                                                    (bits16) 0x0,
 134                                                    (AttrNumber) 1,
 135                                                    (RegProcedure) F_OIDEQ,
 136                                                    ObjectIdGetDatum(loid));
 137
 138         pg_largeobject = heap_openr(LargeObjectRelationName, RowShareLock);
 139         pg_lo_idx = index_openr(LargeObjectLOidPNIndex);
 140
 141         sd = index_beginscan(pg_largeobject, pg_lo_idx, SnapshotNow, 1, skey);
 142
 143         if ((tuple = index_getnext(sd, ForwardScanDirection)) != NULL)
 144                 retval = true;
 145
 146         index_endscan(sd);
 147
 148         index_close(pg_lo_idx);
 149         heap_close(pg_largeobject, RowShareLock);
 150
 151         return retval;
 152 }