55 * contains the user-level large object application interface routines.
66 *
77 *
8+ * Note: we access pg_largeobject.data using its C struct declaration.
9+ * This is safe because it immediately follows pageno which is an int4 field,
10+ * and therefore the data field will always be 4-byte aligned, even if it
11+ * is in the short 1-byte-header format. We have to detoast it since it's
12+ * quite likely to be in compressed or short format. We also need to check
13+ * for NULLs, since initdb will mark loid and pageno but not data as NOT NULL.
14+ *
815 * Note: many of these routines leak memory in CurrentMemoryContext, as indeed
916 * does most of the backend code. We expect that CurrentMemoryContext will
1017 * be a short-lived context. Data that must persist across function calls
1724 *
1825 *
1926 * IDENTIFICATION
20- * $PostgreSQL: pgsql/src/backend/storage/large_object/inv_api.c,v 1.124 2007/04/06 04:21:42 tgl Exp $
27+ * $PostgreSQL: pgsql/src/backend/storage/large_object/inv_api.c,v 1.125 2007/06/12 19:46:24 tgl Exp $
2128 *
2229 *-------------------------------------------------------------------------
2330 */
@@ -330,8 +337,10 @@ inv_getsize(LargeObjectDesc *obj_desc)
330337bool pfreeit ;
331338
332339found = true;
340+ if (HeapTupleHasNulls (tuple ))/* paranoia */
341+ elog (ERROR ,"null field found in pg_largeobject" );
333342data = (Form_pg_largeobject )GETSTRUCT (tuple );
334- datafield = & (data -> data );
343+ datafield = & (data -> data );/* see note at top of file */
335344pfreeit = false;
336345if (VARATT_IS_EXTENDED (datafield ))
337346{
@@ -434,6 +443,8 @@ inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes)
434443bytea * datafield ;
435444bool pfreeit ;
436445
446+ if (HeapTupleHasNulls (tuple ))/* paranoia */
447+ elog (ERROR ,"null field found in pg_largeobject" );
437448data = (Form_pg_largeobject )GETSTRUCT (tuple );
438449
439450/*
@@ -457,7 +468,7 @@ inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes)
457468off = (int ) (obj_desc -> offset - pageoff );
458469Assert (off >=0 && off < LOBLKSIZE );
459470
460- datafield = & (data -> data );
471+ datafield = & (data -> data );/* see note at top of file */
461472pfreeit = false;
462473if (VARATT_IS_EXTENDED (datafield ))
463474{
@@ -558,6 +569,8 @@ inv_write(LargeObjectDesc *obj_desc, const char *buf, int nbytes)
558569{
559570if ((oldtuple = index_getnext (sd ,ForwardScanDirection ))!= NULL )
560571{
572+ if (HeapTupleHasNulls (oldtuple ))/* paranoia */
573+ elog (ERROR ,"null field found in pg_largeobject" );
561574olddata = (Form_pg_largeobject )GETSTRUCT (oldtuple );
562575Assert (olddata -> pageno >=pageno );
563576}
@@ -575,7 +588,7 @@ inv_write(LargeObjectDesc *obj_desc, const char *buf, int nbytes)
575588 *
576589 * First, load old data into workbuf
577590 */
578- datafield = & (olddata -> data );
591+ datafield = & (olddata -> data );/* see note at top of file */
579592pfreeit = false;
580593if (VARATT_IS_EXTENDED (datafield ))
581594{
@@ -737,6 +750,8 @@ inv_truncate(LargeObjectDesc *obj_desc, int len)
737750olddata = NULL ;
738751if ((oldtuple = index_getnext (sd ,ForwardScanDirection ))!= NULL )
739752{
753+ if (HeapTupleHasNulls (oldtuple ))/* paranoia */
754+ elog (ERROR ,"null field found in pg_largeobject" );
740755olddata = (Form_pg_largeobject )GETSTRUCT (oldtuple );
741756Assert (olddata -> pageno >=pageno );
742757}
@@ -749,7 +764,7 @@ inv_truncate(LargeObjectDesc *obj_desc, int len)
749764if (olddata != NULL && olddata -> pageno == pageno )
750765{
751766/* First, load old data into workbuf */
752- bytea * datafield = & (olddata -> data );
767+ bytea * datafield = & (olddata -> data );/* see note at top of file */
753768bool pfreeit = false;
754769int pagelen ;
755770