Re: [Proposal] Global temporary tables

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
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