Repair longstanding error in btree xlog replay: XLogReadBuffer should be

passed extend = true whenever we are reading a page we intend to reinitialize
completely, even if we think the page "should exist".  This is because it
might indeed not exist, if the relation got truncated sometime after the
current xlog record was made and before the crash we're trying to recover
from.  These two thinkos appear to explain both of the old bug reports
discussed here:
http://archives.postgresql.org/pgsql-hackers/2005-05/msg01369.php

diff --git a/src/backend/access/nbtree/nbtxlog.c b/src/backend/access/nbtree/nbtxlog.c
index 8351926f2cfc83b508fb3e19543bc6ed45713e02..12425ee873416ddd7dfd65c5a46098f8e2c74a0e 100644 (file)
--- a/src/backend/access/nbtree/nbtxlog.c
+++ b/src/backend/access/nbtree/nbtxlog.c
@@ -251,7 +251,7 @@ btree_xlog_split(bool redo, bool onleft, bool isroot,
        rightsib = (onleft) ? xlrec->otherblk : targetblk;
 
        /* Left (original) sibling */
-       buffer = XLogReadBuffer(false, reln, leftsib);
+       buffer = XLogReadBuffer(true, reln, leftsib);
        if (!BufferIsValid(buffer))
                elog(PANIC, "btree_split_%s: lost left sibling", op);
 
@@ -524,7 +524,7 @@ btree_xlog_delete_page(bool redo, bool ismeta,
        }
 
        /* Rewrite target page as empty deleted page */
-       buffer = XLogReadBuffer(false, reln, target);
+       buffer = XLogReadBuffer(true, reln, target);
        if (!BufferIsValid(buffer))
                elog(PANIC, "btree_delete_page_%s: lost target page", op);
        page = (Page) BufferGetPage(buffer);