From: | Anastasia Lubennikova <lubennikovaav(at)gmail(dot)com> |
---|---|
To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Index-only scans for GIST |
Date: | 2014-08-17 16:15:38 |
Message-ID: | CAP4vRV4DZAqSR_h_i9xurum45uPK3bAkMvR619_b0YVbLVff4Q@mail.gmail.com |
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Lists: | pgsql-hackers |
2014-08-07 0:30 GMT+04:00 Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>:
* I'm getting two regression failures with this (opr_sanity and join).
>
opr_sanity failure is corrected.
But there is remain question with join.
I check the latest version of my github repo and there's no fail in join
regression test
All 145 tests passed.
To tell the truth, I don't understand which changes could led to this
failure.
Could you show me regression diffs?
I want to understand what's wrong with the patch.
* The regression test queries that use LIMIT are not guaranteed to always
> return the same rows, hence they're not very good regression test cases.
> I'd suggest using more restricting WHERE clauses, so that each query only
> returns a handful of rows.
>
Thank you for comment, I rewrote wrong queries. But could you explain why
LIMIT queries may return different results? Is it happens because of
different query optimization?
* I think it's leaking memory, in GIST scan context. I tested this with a
> variant of the regression tests:
>
> insert into gist_tbl select box(point(0.05*i, 0.05*i), point(0.05*i,
> 0.05*i)),
> point(0.05*i, 0.05*i) FROM generate_series(0,
> 10000000) as i;
> CREATE INDEX gist_tbl_point_index ON gist_tbl USING gist (p);
>
> set enable_seqscan=off;
> set enable_bitmapscan=off;
>
> explain analyze select p from gist_tbl where p <@ box(point(0,0),
> point(9999999,9999999)) and length(p::text) < 10;
>
> while the final query runs, 'top' shows constantly increasing memory usage.
I don't think it's memory leak. After some increasing, memory using remain
the same. It works similar without using indexonlyscan.
--
Best regards,
Lubennikova Anastasia
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