Re: [HACKERS] [PROPOSAL] Use SnapshotAny in get_actual_variable_range - Mailing list pgsql-hackers

From Tom Lane
Subject Re: [HACKERS] [PROPOSAL] Use SnapshotAny in get_actual_variable_range
Date
Msg-id 17753.1493328834@sss.pgh.pa.us
Whole thread Raw
In response to Re: [HACKERS] [PROPOSAL] Use SnapshotAny in get_actual_variable_range  (Andres Freund <andres@anarazel.de>)
Responses Re: [HACKERS] [PROPOSAL] Use SnapshotAny in get_actual_variable_range
List pgsql-hackers
Andres Freund <andres@anarazel.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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