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From: Tomas Vondra <[email protected]>
To: Konstantin Knizhnik <[email protected]>
Cc: 曾文旌(义从) <[email protected]>
Cc: Pavel Stehule <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: 蔡松露(子嘉) <[email protected]>
Cc: Cai, Le <[email protected]>
Cc: 萧少聪(铁庵) <[email protected]>
Subject: Re: [Proposal] Global temporary tables
Date: Sun, 12 Jan 2020 02:14:01 +0100
Message-ID: <20200112011401.zwvvxoywrrivl542@development> (raw)
In-Reply-To: <[email protected]>
References: <CAFj8pRBo8YZ=bJESqf2fkxGL8Bq2Fs7=SjxisS7UhXHh6yPSfA@mail.gmail.com>
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	<[email protected]>

On Fri, Jan 10, 2020 at 03:24:34PM +0300, Konstantin Knizhnik wrote:
>
>
>On 09.01.2020 19:30, Tomas Vondra wrote:
>
>
>>
>>>
>>>>
>>>>>3 Still no one commented on GTT's transaction information 
>>>>>processing, they include
>>>>>3.1 Should gtt's frozenxid need to be care?
>>>>>3.2 gtt’s clog clean
>>>>>3.3 How to deal with "too old" gtt data
>>>>>
>>>>
>>>>No idea what to do about this.
>>>>
>>>
>>>I wonder what is the specific of GTT here?
>>>The same problem takes place for normal (local) temp tables, doesn't it?
>>>
>>
>>Not sure. TBH I'm not sure I understand what the issue actually is.
>
>Just open session, create temporary table and insert some data in it.
>Then in other session run 2^31 transactions (at my desktop it takes 
>about 2 hours).
>As far as temp tables are not proceeded by vacuum, database is stalled:
>
> ERROR:  database is not accepting commands to avoid wraparound data 
>loss in database "postgres"
>
>It seems to be quite dubious behavior and it is strange to me that 
>nobody complains about it.
>We discuss  many issues related with temp tables (statistic, parallel 
>queries,...) which seems to be less critical.
>
>But this problem is not specific to GTT - it can be reproduced with 
>normal (local) temp tables.
>This is why I wonder why do we need to solve it in GTT patch.
>

Yeah, I think that's out of scope for GTT patch. Once we solve it for
plain temporary tables, we'll solve it for GTT too.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services 

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