Re: Index-only scans for GIST - Mailing list pgsql-hackers

From Anastasia Lubennikova
Subject Re: Index-only scans for GIST
Date
Msg-id CAP4vRV4DZAqSR_h_i9xurum45uPK3bAkMvR619_b0YVbLVff4Q@mail.gmail.com
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In response to Re: Index-only scans for GIST  (Heikki Linnakangas <hlinnakangas@vmware.com>)
Responses Re: Index-only scans for GIST
Re: Index-only scans for GIST
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2014-08-07 0:30 GMT+04:00 Heikki Linnakangas <hlinnakangas@vmware.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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