Re: Incorrect visibility test function assigned to snapshot

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От Alvaro Herrera
Тема Re: Incorrect visibility test function assigned to snapshot
Дата
Msg-id 20180530132854.tkv37qiamepu3slh@alvherre.pgsql
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Ответ на Incorrect visibility test function assigned to snapshot  (Antonin Houska <ah@cybertec.at>)
Ответы Re: Incorrect visibility test function assigned to snapshot  (Antonin Houska <ah@cybertec.at>)
Re: Incorrect visibility test function assigned to snapshot  (Bruce Momjian <bruce@momjian.us>)
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On 2018-May-30, Antonin Houska wrote:

> In the header comment, SnapBuildInitialSnapshot() claims to set
> snapshot->satisfies to the HeapTupleSatisfiesMVCC test function, and indeed it
> converts the "xid" array to match its semantics (i.e. the xid items eventually
> represent running transactions as opposed to the committed ones). However the
> test function remains HeapTupleSatisfiesHistoricMVCC as set by
> SnapBuildBuildSnapshot().

Interesting.  While this sounds like an oversight that should have
horrible consequences, it's seems not to because the current callers
don't seem to care about the ->satisfies function.  Are you able to come
up with some scenario in which it causes an actual problem?

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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