>>If an idx is faster than a cdx, and the index expression is the same, you must have some kind of data corruption. I suggest that you find the cause of this error instead of trying to fix the consequences of the error.
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>How could that be possible ?
>I have rebuilt the indexes (cdx) Just before running the tests
>Is it possible ?????

Did you use REINDEX or did you rebuild them from scratch? REINDEX can keep corruption, so DELETE the tags and build them again and see whether the problems goes away.

Also, I would rethink the idea of running a query inside a SCAN loop. Why not gather all the information once with a single query and then just process it in a loop.

Tamar