Dmitry Tkach <[EMAIL PROTECTED]> writes:
explain select * from abc where a=1 and b in (1,2); Now, why doesn't it want to use the index for the second condition???
Because the expression preprocessor prefers CNF (AND of ORs) over DNF (OR of ANDs). Since your WHERE clause is already CNF, it won't convert to DNF, which unfortunately is what's needed to produce a multiple indexscan. For now you have to write something like
WHERE (a=1 and b=1) OR (a=1 and b=2)
to get a multiple indexscan from this. (Actually, it would work if b were the first index column --- you need OR clauses that all mention the first index column to trigger consideration of a multiple indexscan.)
Improving this is on the TODO list, but fixing it in a reasonable way seems to require a major rethinking of the way multi-indexscans are planned.
That's what I suspected... In fact, I even tried converting it to the DNF, and it worked...
My problem is that this was just an example, the real query is a lot more complicated (joining about 10 tables), and the list is about 20 elements :-(
Dima
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