Yes, it really depends on Locale. If I created a database with Locale = C, the problem won't happen (at least so far). BTW, I forgot to mention I tested with some Chinese and Japanese characters.
However, it raises another issue why a wrong Locale would damage index? It shall only affect records with wrong conversion, not something like '1000'.
Search the list archives for LIKE and locale - different locales have different sorting rules. Setting locale=C makes everything simple.
With 8.0 you can define your own operator classes to tell PG it can use an index (see ch 11.6 of the manuals). I think there are examples in the mailing-list archives.
-- Richard Huxton Archonet Ltd
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