(ITS#5086) back-bdb bug when add is used with snapshot isolation

[stelios.xx.grigoriadis@ericsson.com]

Full_Name: Stelios Grigoriadis
Version: 2.3.32
OS: Linux, (SLES 10)
URL: http://ninikos.freehostia.com/bdb_idl_cache_bug.tar.gz
Submission from: (NULL) (194.237.142.7)


When using slapd with the snapshot isolation level in DB (version 4.5.20)
it is possible that added entries don't appear in subsequent searches.

Scenario: A client is adding new information while at the same time another
is initiating an LDAP search with the same searchbase as the "parent" of
the added information.
If the search is executed after the add operation has cleared the IDL-cache
but before the changes has been committed, the added entries will not appear
in any subsequent searches unless slapd is restarted.

The problem is that, in the bdb_idl_insert_key-function, the key is deleted
from the IDL-cache but the newly added keys in the database are not yet
committed, so clients that re-read the information will not have those updated
keys.

The solution would be to clear the relevant IDL-cache entries after the
changes has been committed.

This behaviour is demonstrated by the program cache_test_fork.c which is
supplied
in bdb_idl_cache_bug.tar.gz along with the slapd configuration.

I am currently working on the solution but would greatly appreciate any help
from you as I am not nearly as familiar with the code as you are.