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Diffstat (limited to 'src/backend/catalog/pg_largeobject.c')
| -rw-r--r-- | src/backend/catalog/pg_largeobject.c | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/src/backend/catalog/pg_largeobject.c b/src/backend/catalog/pg_largeobject.c new file mode 100644 index 00000000000..c471a9ae139 --- /dev/null +++ b/src/backend/catalog/pg_largeobject.c @@ -0,0 +1,184 @@ +/*------------------------------------------------------------------------- + * + * pg_largeobject.c + * routines to support manipulation of the pg_largeobject relation + * + * Portions Copyright (c) 1996-2000, PostgreSQL, Inc + * Portions Copyright (c) 1994, Regents of the University of California + * + * + * IDENTIFICATION + * $Header: /cvsroot/pgsql/src/backend/catalog/pg_largeobject.c,v 1.5 2000/10/24 01:38:23 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. + * + * Return value is OID assigned to the page tuple (any use in it?) + */ +Oid +LargeObjectCreate(Oid loid) +{ + Oid retval; + 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 + */ + retval = 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); + + return retval; +} + +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); + pfree(indexRes); + if (tuple.t_data != NULL) + { + heap_delete(pg_largeobject, &tuple.t_self, NULL); + 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); + 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; +} |