Re: New vacuum option to do only freezing

From: "Bossart, Nathan" <bossartn(at)amazon(dot)com>
To: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: New vacuum option to do only freezing
Date: 2019-02-04 21:22:38
Message-ID: A959EFE3-3858-4E82-9993-AE9A82785544@amazon.com
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On 2/3/19, 1:48 PM, "Masahiko Sawada" <sawada(dot)mshk(at)gmail(dot)com> wrote:
> On Sat, Feb 2, 2019 at 7:00 PM Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> wrote:
>>
>> On 2019-Feb-01, Bossart, Nathan wrote:
>>
>> > IMHO we could document this feature at a slightly higher level without
>> > leaving out any really important user-facing behavior. Here's a quick
>> > attempt to show what I am thinking:
>> >
>> > With this option, VACUUM skips all index cleanup behavior and
>> > only marks tuples as "dead" without reclaiming the storage.
>> > While this can help reclaim transaction IDs faster to avoid
>> > transaction ID wraparound (see Section 24.1.5), it will not
>> > reduce bloat.
>>
>> Hmm ... don't we compact out the storage for dead tuples? If we do (and
>> I think we should) then this wording is not entirely correct.
>
> Yeah, we remove tuple and leave the dead ItemId. So we actually
> reclaim the almost tuple storage.

Ah, yes. I was wrong here. Thank you for clarifying.

> Attached the updated patch and the patch for vacuumdb.

Thanks! I am hoping to take a deeper look at this patch in the next
couple of days.

Nathan

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