Horton

Re: BUG #18213: Standby's repeatable read isolation level transaction encountered a "nonrepeatable read" problem

feichanghong <feichanghong@qq.com>

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From: 费长红 <feichanghong@qq.com>
To: zhihuifan1213 <zhihuifan1213@163.com>
Cc: pgsql-bugs <pgsql-bugs@lists.postgresql.org>
Date: 2023-12-05T11:47:27Z
Lists: pgsql-bugs

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix timing-dependent failure in GSSAPI data transmission.

Attachments

Yes, the existing "ProcArrayGetReplicationSlotXmin" function has met the functional requirements and I have updated it in the attachment.




Best regards,


Changhong Fei


------------------&nbsp;Original&nbsp;------------------
From:                                                                                                                        "zhihuifan1213"                                                                                    <zhihuifan1213@163.com&gt;;
Date:&nbsp;Wed, Nov 29, 2023 03:50 PM
To:&nbsp;"费长红"<feichanghong@qq.com&gt;;
Cc:&nbsp;"pgsql-bugs"<pgsql-bugs@lists.postgresql.org&gt;;
Subject:&nbsp;Re: 回复： BUG #18213: Standby's repeatable read isolation level transaction encountered a "nonrepeatable read" problem




"费长红" <feichanghong@qq.com&gt; writes:

&gt; -------------------------------------------------------------------------------------------------------------------------
&gt;
&gt;&nbsp; *&nbsp; 起个啥名好呢&nbsp; 
&gt;&nbsp;&nbsp;&nbsp; feichanghong@qq.com&nbsp; 
&gt;&nbsp; 
&gt; Indeed, I simply implemented and verified the solution. In the above test, the "create index" command on RW will hang
&gt; until the transaction on standby is committed or aborted.

I think this is acceptable since its behavior is same as we wait for the
transactions in primary.

&gt; In addition, even if there is no select query on the standby, RW's "create index" command may wait for a period of time,
&gt; which affected by the wal_receiver_status_interval parameter.

The "wait" happens at the very last of index building, so the building
stages gives an enough time for standby to exceeds the xmin, so in a
real case, I think the overhead will be pretty low. 

&gt; You can see attachment for the patch.

I take a look at the that, function GetReplicationSlotXmin should be not
needed. You can use ProcArrayGetReplicationSlotXmin directly.

After searching the caller of WaitForOlderSnapshots, I think this bug
probably has impact on "deteach partition concurrently" / "reindex
concurrently" features.&nbsp; All of them needs the same fix. 

-- 
Best Regards
Andy Fan