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
