diff options
Diffstat (limited to 'src/backend/access/nbtree/nbtpage.c')
| -rw-r--r-- | src/backend/access/nbtree/nbtpage.c | 44 |
1 files changed, 35 insertions, 9 deletions
diff --git a/src/backend/access/nbtree/nbtpage.c b/src/backend/access/nbtree/nbtpage.c index bc0ed6641f7..a4c6c0b974c 100644 --- a/src/backend/access/nbtree/nbtpage.c +++ b/src/backend/access/nbtree/nbtpage.c @@ -9,7 +9,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.74 2003/12/21 01:23:06 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.75 2004/04/21 18:24:25 tgl Exp $ * * NOTES * Postgres btree pages look like ordinary relation pages. The opaque @@ -262,11 +262,15 @@ _bt_getroot(Relation rel, int access) Assert(rootblkno != P_NONE); rootlevel = metad->btm_fastlevel; - _bt_relbuf(rel, metabuf); /* done with the meta page */ + /* + * We are done with the metapage; arrange to release it via + * first _bt_relandgetbuf call + */ + rootbuf = metabuf; for (;;) { - rootbuf = _bt_getbuf(rel, rootblkno, BT_READ); + rootbuf = _bt_relandgetbuf(rel, rootbuf, rootblkno, BT_READ); rootpage = BufferGetPage(rootbuf); rootopaque = (BTPageOpaque) PageGetSpecialPointer(rootpage); @@ -278,8 +282,6 @@ _bt_getroot(Relation rel, int access) elog(ERROR, "no live root page found in \"%s\"", RelationGetRelationName(rel)); rootblkno = rootopaque->btpo_next; - - _bt_relbuf(rel, rootbuf); } /* Note: can't check btpo.level on deleted pages */ @@ -352,11 +354,15 @@ _bt_gettrueroot(Relation rel) rootblkno = metad->btm_root; rootlevel = metad->btm_level; - _bt_relbuf(rel, metabuf); /* done with the meta page */ + /* + * We are done with the metapage; arrange to release it via + * first _bt_relandgetbuf call + */ + rootbuf = metabuf; for (;;) { - rootbuf = _bt_getbuf(rel, rootblkno, BT_READ); + rootbuf = _bt_relandgetbuf(rel, rootbuf, rootblkno, BT_READ); rootpage = BufferGetPage(rootbuf); rootopaque = (BTPageOpaque) PageGetSpecialPointer(rootpage); @@ -368,8 +374,6 @@ _bt_gettrueroot(Relation rel) elog(ERROR, "no live root page found in \"%s\"", RelationGetRelationName(rel)); rootblkno = rootopaque->btpo_next; - - _bt_relbuf(rel, rootbuf); } /* Note: can't check btpo.level on deleted pages */ @@ -493,6 +497,28 @@ _bt_getbuf(Relation rel, BlockNumber blkno, int access) } /* + * _bt_relandgetbuf() -- release a locked buffer and get another one. + * + * This is equivalent to _bt_relbuf followed by _bt_getbuf, with the + * exception that blkno may not be P_NEW. Also, if obuf is InvalidBuffer + * then it reduces to just _bt_getbuf; allowing this case simplifies some + * callers. The motivation for using this is to avoid two entries to the + * bufmgr when one will do. + */ +Buffer +_bt_relandgetbuf(Relation rel, Buffer obuf, BlockNumber blkno, int access) +{ + Buffer buf; + + Assert(blkno != P_NEW); + if (BufferIsValid(obuf)) + LockBuffer(obuf, BUFFER_LOCK_UNLOCK); + buf = ReleaseAndReadBuffer(obuf, rel, blkno); + LockBuffer(buf, access); + return buf; +} + +/* * _bt_relbuf() -- release a locked buffer. * * Lock and pin (refcount) are both dropped. Note that either read or |