[GENERAL] Avoiding sequential scans with OR join condition

[Mike Mascari]

Hello. I have a query like:
SELECT big_table.*
FROM little_table, big_table
WHERE little_table.x = 10 AND
little_table.y IN (big_table.y1, big_table.y2);
I have indexes on both big_table.y1 and big_table.y2 and on 
little_table.x and little_table.y. The result is a sequential scan of 
big_table. In order to prevent this, I've rewritten the query as:

SELECT big_table.*
FROM little_table, big_table
WHERE little_table.x = 10 AND
little_table.y = big_table.y1
 UNION
SELECT big_table.*
FROM little_table, big_table
WHERE little_table.x = 10 AND
little_table.y = big_table.y2
which does allow an index scan, but suffers from two separate queries 
along with a unique sort, which, from the data, represents 90% of the 
tuples returned by both queries.

Is there any way to write the first query such that indexes will be used?
Mike Mascari
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