Re: Optimization for lazy_scan_heap

On 4 August 2016 at 05:57, Masahiko Sawada <sawada.mshk@gmail.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?

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