Restore from online backup, query from pg_proc, got wrong result, please see the problem!

After restoring from online backup and archive xlog files, I query pg_proc using SQL: select * from pg_proc where
proname= 'xxx' and oid = XXX. I got no result back, but when using SQL:select * from pg_proc where proname = 'xxx', I
gotwhat I want, and the result OID is just the one in the first SQL.Then I reindex pg_proc, retry the first SQL, the
resultis correct. 
Any one konw what is the matter?  How can I solve this without reindexing the table!

PS: I am using PG8.3.7

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Richard
2010-08-11