| From: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
|---|---|
| To: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Optimization for lazy_scan_heap |
| Date: | 2016-09-05 09:27:53 |
| Message-ID: | CANP8+jLj0xN-3VgYaZfbg-XbtFU=9u=qXS+RhycGk5o7NrPMJg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 4 August 2016 at 05:57, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> While reviewing freeze map code, Andres pointed out[1] that
> lazy_scan_heap could accesses visibility map twice and its logic is
> seems a bit tricky.
> As discussed before, it's not nice especially when large relation is
> entirely frozen.
>
> I posted the patch for that before but since this is an optimization,
> not bug fix, I'd like to propose it again.
> Please give me feedback.
>
> [1] https://www.postgresql.org/message-id/20160505000840.epatoq6d2e556446%40alap3.anarazel.de
If we have a freeze map now, surely tables will no longer be entirely frozen?
What performance difference does this make, in a realistic use case?
How would we test this to check it is exactly correct?
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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