1010 *
1111 *
1212 * IDENTIFICATION
13- * $Header: /cvsroot/pgsql/src/backend/storage/smgr/smgr.c,v 1.4 1996/11/08 05:59:15 momjian Exp $
13+ * $Header: /cvsroot/pgsql/src/backend/storage/smgr/smgr.c,v 1.5 1996/11/27 07:25:52 vadim Exp $
1414 *
1515 *-------------------------------------------------------------------------
1616 */
@@ -36,6 +36,7 @@ typedef struct f_smgr {
3636int (* smgr_flush )();
3737int (* smgr_blindwrt )();
3838int (* smgr_nblocks )();
39+ int (* smgr_truncate )();
3940int (* smgr_commit )();/* may be NULL */
4041int (* smgr_abort )();/* may be NULL */
4142}f_smgr ;
@@ -49,12 +50,14 @@ static f_smgr smgrsw[] = {
4950
5051/* magnetic disk */
5152 {mdinit ,NULL ,mdcreate ,mdunlink ,mdextend ,mdopen ,mdclose ,
52- mdread ,mdwrite ,mdflush ,mdblindwrt ,mdnblocks ,mdcommit ,mdabort },
53+ mdread ,mdwrite ,mdflush ,mdblindwrt ,mdnblocks ,mdtruncate ,
54+ mdcommit ,mdabort },
5355
5456#ifdef MAIN_MEMORY
5557/* main memory */
5658 {mminit ,mmshutdown ,mmcreate ,mmunlink ,mmextend ,mmopen ,mmclose ,
57- mmread ,mmwrite ,mmflush ,mmblindwrt ,mmnblocks ,mmcommit ,mmabort },
59+ mmread ,mmwrite ,mmflush ,mmblindwrt ,mmnblocks ,NULL ,
60+ mmcommit ,mmabort },
5861
5962#endif /* MAIN_MEMORY */
6063};
@@ -321,6 +324,29 @@ smgrnblocks(int16 which, Relation reln)
321324return (nblocks );
322325}
323326
327+ /*
328+ * smgrtruncate() -- Truncate supplied relation to a specified number
329+ *of blocks
330+ *
331+ *Returns the number of blocks on success, aborts the current
332+ *transaction on failure.
333+ */
334+ int
335+ smgrtruncate (int16 which ,Relation reln ,int nblocks )
336+ {
337+ int newblks ;
338+
339+ newblks = nblocks ;
340+ if (smgrsw [which ].smgr_truncate )
341+ {
342+ if ((newblks = (* (smgrsw [which ].smgr_truncate ))(reln ,nblocks ))< 0 )
343+ elog (WARN ,"cannot truncate %.*s to %d blocks" ,
344+ NAMEDATALEN ,& (reln -> rd_rel -> relname .data [0 ]),nblocks );
345+ }
346+
347+ return (newblks );
348+ }
349+
324350/*
325351 * smgrcommit(), smgrabort() -- Commit or abort changes made during the
326352 * current transaction.