| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Dmitriy Sarafannikov <dsarafannikov(at)yandex(dot)ru>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Borodin Vladimir <root(at)simply(dot)name>, Хомик Кирилл <khomikki(at)yandex-team(dot)ru> |
| Subject: | Re: [PROPOSAL] Use SnapshotAny in get_actual_variable_range |
| Date: | 2017-04-27 21:33:54 |
| Message-ID: | 17753.1493328834@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2017-04-27 17:22:25 -0400, Tom Lane wrote:
>> How so? Shouldn't the indexscan go back and mark such tuples dead in
>> the index, such that they'd be visited this way only once? If that's
>> not happening, maybe we should try to fix it.
> One way that never happens is if you end up choosing bitmap index scans
> all the time...
What I'm thinking of is the regular indexscan that's done internally
by get_actual_variable_range, not whatever ends up getting chosen as
the plan for the user query. I had supposed that that would kill
dead index entries as it went, but maybe that's not happening for
some reason.
regards, tom lane
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