[CI] BHUNT comparison experiments

[Hideaki Kimura]

> You can play with enable_seqscan to force index lookups globally.
I did
   SET enable_seqscan = FALSE;
but nothing has changed. How can I disable seqscan?

>> So, I split the query to
>> SELECT DISTINCT CATID FROM EXCEPTIONS WHERE PRICE BETWEEN 1000 AND 1100
> 
> How's the performance without the DISTINCT in the inner select?
I'll try.

> Hmm, are the union-ed CATIDs just the exception table IDs, or all
> relevant IDs? How would BHUNT get from 'CATID BETWEEN 20 AND 33' to
> this step?

All relevant IDs. In this case,
SELECT COUNT(DISTINCT CAT3) FROM ITEMS WHERE PRICE BETWEEN 1000 AND 1100 
AND CATID IN (18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,35,37)

BHUNT will manually concat 20-33 and the exceptions.
-- 
Hideaki Kimura <hkimura at cs.brown.edu>