[Zodb-checkins] CVS: ZODB3 - NEWS.txt:1.17.2.25

[Jeremy Hylton]

Update of /cvs-repository/ZODB3
In directory cvs.zope.org:/tmp/cvs-serv784

Modified Files:
      Tag: ZODB3-3_1-branch
	NEWS.txt 
Log Message:
Backport atomic invalidations code.


=== ZODB3/NEWS.txt 1.17.2.24 => 1.17.2.25 ===
--- ZODB3/NEWS.txt:1.17.2.24	Wed Apr 30 15:41:46 2003
+++ ZODB3/NEWS.txt	Wed Apr 30 16:37:04 2003
@@ -4,6 +4,17 @@
 ZODB
 ----
 
+Invalidations are now processed atomically.  Each transaction will see
+all the changes caused by an earlier transaction or none of them.
+Before this patch, it was possible for a transaction to see invalid
+data because it saw only a subset of the invalidations.  This is the
+most likely cause of reported BTrees corruption, where keys were
+stored in the wrong bucket.  When a BTree bucket splits, the bucket
+and the bucket's parent are both modified.  If a transaction sees the
+invalidation for the bucket but not the parent, the BTree in memory
+will be internally inconsistent and keys can be put in the wrong
+bucket.  The atomic invalidation fix prevents this problem.
+
 A number of minor reference count fixes in the object cache were
 fixed.  That's the cPickleCache.c file.