modify/add: <ATTRIBUTE>: merge error

[Charles Stephens <cfs@cowlabs.com>]

We are running on RH9+mods Linux 2.4.20 using OpenLDAP 2.3.11.  Very  
recently, I've been gettings merge errors in our reject files when a  
new member is added to a posixGroup object with lots of members  
(10,000+).  Here are excerpts from the reject file (some data has  
been scrubbed):

ERROR: Internal (implementation specific) error: modify/add:  
memberUid: merge error
replica: replica10.cowlabs.com:389
time: 1143021501.0
dn: cn=biggroup,ou=Posix,ou=Groups,dc=cowlabs,dc=com
changetype: modify
add: memberUid
memberUid: anewuser
-
add: member
member: uid=anewuser,ou=People,dc=google,dc=com
-
replace: entryCSN
entryCSN: 20060322095819Z#000001#00#000000
-
replace: modifiersName
modifiersName: uid=groups_agent,ou=people,dc=cowlabs,dc=com
-
replace: modifyTimestamp
modifyTimestamp: 20060322095819Z
-

In the logs, we can find the corresponding actual MOD attempt:

Mar 22 01:58:23 replica10 slapd[13901]: conn=146642 op=2210 MOD  
dn="cn=abiggroup,ou=Posix,ou=Groups,dc=cowlabs,dc=com"
Mar 22 01:58:23 replica10 slapd[13901]: conn=146642 op=2210 MOD  
attr=memberUid member
entryCSN modifiersName modifyTimestamp
Mar 22 01:58:23 replica10 slapd[13901]: conn=146642 op=2210 RESULT  
tag=103 err=80 text=modify/add: memberUid: merge error