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Re: [PATCH] remove condition always true(/src/backend/access/heap/vacuumlazy.c) - Mailing list pgsql-hackers

From Andres Freund
Subject Re: [PATCH] remove condition always true(/src/backend/access/heap/vacuumlazy.c)
Date
Msg-id 20200330190505.3ep6gbagdha24bjy@alap3.anarazel.de
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In response to [PATCH] remove condition always true (/src/backend/access/heap/vacuumlazy.c)  (Ranier Vilela <ranier.vf@gmail.com>)
List pgsql-hackers
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Hi,

On 2020-03-30 15:07:40 -0300, Ranier Vilela wrote:
> I'm not sure that the patch is 100% correct.

This is *NOT* correct.


> But the fix is about expression about always true.
> But if this patch is correct, he fix one possible bug.
> 
> The comment says:
> * Perform checking of FSM after releasing lock, the fsm is
> * approximate, after all.
> 
> But this is not what the code does, apparently it checks before unlocking.

No, it doesn't. The freespace check isn't the PageIsNew(), it's the
GetRecordedFreeSpace() call. Which happens after unlocking.

Greetings,

Andres Freund

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