Help, how to get sub-select to look at index?

Hello,

The outer SELECT in a stament that uses sub selects appears not
to ever make use of index files. Here is an example

(1) select * from foo where bar = 1;

The above will use an index if one exists. It is very fast
even on my 3 million row table.

(2) select * from foo where bar IN (SELECT 1)

The above seems to always do a sequencial scan of the
table It is very slow on my 3 million row table.

My real code is more complex. The inner select returns about 100
rows which triggers about 100 sequencial scans of my 3 million row
table. I let it run for hours and I have never seen it finish.
(I use a 2000 block buffer chache and disabled fsync)

Is there a trick I could use? Can you type cast a subselect?
I have both btree and hash indexes
built and did a fresh vacuum. Still no luck. Just thought I'd
ask before writting a libpg C program to simulate (2).

(Please cc a direct reply)

Thanks,

--
--Chris Albertson

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Logicon RDA, Pasadena California Fax: 626-351-0699