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/*-------------------------------------------------------------------------
*
* pg_largeobject.c
* routines to support manipulation of the pg_largeobject relation
*
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/catalog/pg_largeobject.c,v 1.10 2001/08/10 20:52:24 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/genam.h"
#include "access/heapam.h"
#include "catalog/catname.h"
#include "catalog/indexing.h"
#include "catalog/pg_largeobject.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
/*
* Create a large object having the given LO identifier.
*
* We do this by inserting an empty first page, so that the object will
* appear to exist with size 0. Note that the unique index will reject
* an attempt to create a duplicate page.
*/
void
LargeObjectCreate(Oid loid)
{
Relation pg_largeobject;
HeapTuple ntup;
Relation idescs[Num_pg_largeobject_indices];
Datum values[Natts_pg_largeobject];
char nulls[Natts_pg_largeobject];
int i;
pg_largeobject = heap_openr(LargeObjectRelationName, RowExclusiveLock);
/*
* Form new tuple
*/
for (i = 0; i < Natts_pg_largeobject; i++)
{
values[i] = (Datum) NULL;
nulls[i] = ' ';
}
i = 0;
values[i++] = ObjectIdGetDatum(loid);
values[i++] = Int32GetDatum(0);
values[i++] = DirectFunctionCall1(byteain,
CStringGetDatum(""));
ntup = heap_formtuple(pg_largeobject->rd_att, values, nulls);
/*
* Insert it
*/
heap_insert(pg_largeobject, ntup);
/*
* Update indices
*/
if (!IsIgnoringSystemIndexes())
{
CatalogOpenIndices(Num_pg_largeobject_indices, Name_pg_largeobject_indices, idescs);
CatalogIndexInsert(idescs, Num_pg_largeobject_indices, pg_largeobject, ntup);
CatalogCloseIndices(Num_pg_largeobject_indices, idescs);
}
heap_close(pg_largeobject, RowExclusiveLock);
heap_freetuple(ntup);
}
void
LargeObjectDrop(Oid loid)
{
bool found = false;
Relation pg_largeobject;
Relation pg_lo_idx;
ScanKeyData skey[1];
IndexScanDesc sd;
RetrieveIndexResult indexRes;
HeapTupleData tuple;
Buffer buffer;
ScanKeyEntryInitialize(&skey[0],
(bits16) 0x0,
(AttrNumber) 1,
(RegProcedure) F_OIDEQ,
ObjectIdGetDatum(loid));
pg_largeobject = heap_openr(LargeObjectRelationName, RowShareLock);
pg_lo_idx = index_openr(LargeObjectLOidPNIndex);
sd = index_beginscan(pg_lo_idx, false, 1, skey);
tuple.t_datamcxt = CurrentMemoryContext;
tuple.t_data = NULL;
while ((indexRes = index_getnext(sd, ForwardScanDirection)))
{
tuple.t_self = indexRes->heap_iptr;
heap_fetch(pg_largeobject, SnapshotNow, &tuple, &buffer, sd);
pfree(indexRes);
if (tuple.t_data != NULL)
{
simple_heap_delete(pg_largeobject, &tuple.t_self);
ReleaseBuffer(buffer);
found = true;
}
}
index_endscan(sd);
index_close(pg_lo_idx);
heap_close(pg_largeobject, RowShareLock);
if (!found)
elog(ERROR, "LargeObjectDrop: large object %u not found", loid);
}
bool
LargeObjectExists(Oid loid)
{
bool retval = false;
Relation pg_largeobject;
Relation pg_lo_idx;
ScanKeyData skey[1];
IndexScanDesc sd;
RetrieveIndexResult indexRes;
HeapTupleData tuple;
Buffer buffer;
/*
* See if we can find any tuples belonging to the specified LO
*/
ScanKeyEntryInitialize(&skey[0],
(bits16) 0x0,
(AttrNumber) 1,
(RegProcedure) F_OIDEQ,
ObjectIdGetDatum(loid));
pg_largeobject = heap_openr(LargeObjectRelationName, RowShareLock);
pg_lo_idx = index_openr(LargeObjectLOidPNIndex);
sd = index_beginscan(pg_lo_idx, false, 1, skey);
tuple.t_datamcxt = CurrentMemoryContext;
tuple.t_data = NULL;
while ((indexRes = index_getnext(sd, ForwardScanDirection)))
{
tuple.t_self = indexRes->heap_iptr;
heap_fetch(pg_largeobject, SnapshotNow, &tuple, &buffer, sd);
pfree(indexRes);
if (tuple.t_data != NULL)
{
retval = true;
ReleaseBuffer(buffer);
break;
}
}
index_endscan(sd);
index_close(pg_lo_idx);
heap_close(pg_largeobject, RowShareLock);
return retval;
}
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