From: | Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> |
---|---|
To: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> |
Cc: | Noah Misch <noah(at)leadboat(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Petr Jelinek <petr(dot)jelinek(at)enterprisedb(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: logical decoding and replication of sequences |
Date: | 2022-08-29 18:04:13 |
Message-ID: | 67acc02f-7989-0bc3-1b19-e5210b7659db@enterprisedb.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On 8/29/22 12:21, Thomas Munro wrote:
> On Mon, Aug 8, 2022 at 8:56 PM Kyotaro Horiguchi
> <horikyota(dot)ntt(at)gmail(dot)com> wrote:
>> At Mon, 08 Aug 2022 17:33:22 +0900 (JST), Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> wrote in
>>> If WaitForWALToBecomeAvailable returned by promotion, ReadPageInteral
>>> misses the chance to inavlidate reader-state. That state is not an
>>> error while in StandbyMode.
>>
>> Mmm... Maybe I wanted to say: (Still I'm not sure the rewrite works..)
>>
>> If WaitForWALToBecomeAvailable returned by promotion, ReadPageInteral
>> would miss the chance to invalidate reader-state. When XLogPageRead
>> is called in blocking mode while in StandbyMode (that is, the
>> traditional condition) , the function continues retrying until it
>> succeeds, or returns XLRAD_FAIL if promote is triggered. In other
>> words, it was not supposed to return non-failure while the header
>> validation is failing while in standby mode. But while in nonblocking
>> mode, the function can return non-failure with lastSourceFailed =
>> true, which seems wrong.
>
> New ideas:
>
> 0001: Instead of figuring out when to invalidate the cache, let's
> just invalidate it before every read attempt. It is only marked valid
> after success (ie state->readLen > 0). No need to worry about error
> cases.
>
Maybe I misunderstand how all this works, but won't this have a really
bad performance impact. If not, why do we need the cache at all?
regards
--
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
From | Date | Subject | |
---|---|---|---|
Next Message | Jeff Davis | 2022-08-29 18:47:16 | Re: New strategies for freezing, advancing relfrozenxid early |
Previous Message | Peter Geoghegan | 2022-08-29 17:25:50 | Re: effective_multixact_freeze_max_age issue |