139 lines
3.1 KiB
C
139 lines
3.1 KiB
C
/*-------------------------------------------------------------------------
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*
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* pg_largeobject.c
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* routines to support manipulation of the pg_largeobject relation
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*
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* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/catalog/pg_largeobject.c,v 1.25 2006/03/05 15:58:23 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/genam.h"
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#include "access/heapam.h"
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#include "catalog/indexing.h"
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#include "catalog/pg_largeobject.h"
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#include "miscadmin.h"
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#include "utils/builtins.h"
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#include "utils/fmgroids.h"
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/*
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* Create a large object having the given LO identifier.
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*
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* We do this by inserting an empty first page, so that the object will
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* appear to exist with size 0. Note that the unique index will reject
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* an attempt to create a duplicate page.
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*/
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void
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LargeObjectCreate(Oid loid)
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{
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Relation pg_largeobject;
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HeapTuple ntup;
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Datum values[Natts_pg_largeobject];
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char nulls[Natts_pg_largeobject];
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int i;
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pg_largeobject = heap_open(LargeObjectRelationId, RowExclusiveLock);
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/*
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* Form new tuple
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*/
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for (i = 0; i < Natts_pg_largeobject; i++)
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{
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values[i] = (Datum) NULL;
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nulls[i] = ' ';
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}
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i = 0;
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values[i++] = ObjectIdGetDatum(loid);
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values[i++] = Int32GetDatum(0);
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values[i++] = DirectFunctionCall1(byteain,
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CStringGetDatum(""));
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ntup = heap_formtuple(pg_largeobject->rd_att, values, nulls);
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/*
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* Insert it
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*/
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simple_heap_insert(pg_largeobject, ntup);
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/* Update indexes */
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CatalogUpdateIndexes(pg_largeobject, ntup);
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heap_close(pg_largeobject, RowExclusiveLock);
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heap_freetuple(ntup);
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}
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void
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LargeObjectDrop(Oid loid)
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{
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bool found = false;
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Relation pg_largeobject;
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ScanKeyData skey[1];
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SysScanDesc sd;
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HeapTuple tuple;
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ScanKeyInit(&skey[0],
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Anum_pg_largeobject_loid,
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BTEqualStrategyNumber, F_OIDEQ,
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ObjectIdGetDatum(loid));
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pg_largeobject = heap_open(LargeObjectRelationId, RowExclusiveLock);
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sd = systable_beginscan(pg_largeobject, LargeObjectLOidPNIndexId, true,
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SnapshotNow, 1, skey);
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while ((tuple = systable_getnext(sd)) != NULL)
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{
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simple_heap_delete(pg_largeobject, &tuple->t_self);
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found = true;
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}
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systable_endscan(sd);
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heap_close(pg_largeobject, RowExclusiveLock);
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if (!found)
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ereport(ERROR,
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(errcode(ERRCODE_UNDEFINED_OBJECT),
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errmsg("large object %u does not exist", loid)));
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}
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bool
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LargeObjectExists(Oid loid)
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{
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bool retval = false;
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Relation pg_largeobject;
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ScanKeyData skey[1];
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SysScanDesc sd;
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/*
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* See if we can find any tuples belonging to the specified LO
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*/
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ScanKeyInit(&skey[0],
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Anum_pg_largeobject_loid,
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BTEqualStrategyNumber, F_OIDEQ,
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ObjectIdGetDatum(loid));
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pg_largeobject = heap_open(LargeObjectRelationId, AccessShareLock);
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sd = systable_beginscan(pg_largeobject, LargeObjectLOidPNIndexId, true,
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SnapshotNow, 1, skey);
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if (systable_getnext(sd) != NULL)
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retval = true;
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systable_endscan(sd);
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heap_close(pg_largeobject, AccessShareLock);
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return retval;
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}
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