Re: Archiving and recovering pg_stat_tmp

> >"You need to have statistics recovered to the same state as they were
> >when you took the FS level backup of your database after shutting down
> >the server."
>
Correct

>
> >"Shutting down" is important since that is when you would have
> >statistics files ($PGDATA/pg_stat/*.stat) available to backup. They
> >capture the statistics as of when the server was shut down.
> Agreed

>What I did:

>
> >1) Collect a few statistics in a result file from a currently running
> >server. For example, the result of the query "select * from
> >pg_stat_user_tables", into say stats1.txt
>
> >2) Clean shut down the server. Take a snapshot of the data directory,
> >"cp -r $pgdata $pgbkp"
>
> >3) Start the server and run a few pgbench tests so that statistics
> >change. Again collect stats, same as in (1) into say stats2.txt
>
> >4) Write $pgbkp/recovery.conf with appropriate restore_command and
> >maybe recovery target (PITR), which I did not, though. Note that we
> >have archiving enabled.
>
> >5) Start the server using -D $pgbkp (may be with port changed for the
> >sake of testing).
>
> >6) After server started in (5) is done recovering and comes online,
> >collect stats again into say stats3.txt
>
> >7) Compare stats3.txt with stats1.txt and stats2.txt.
>
> >8) I observed that stats3.txt == stats1.txt. That is stats after
> >recovery are same as they were when the snapshot was taken.
>
> Thank you for all the effort! A question
>
When server was restarted in (5) which stats file was loaded stats1.txt
or stats.2.txt?. I think it must have been stats1.txt as stats3.txt =
stats1.txt. What happens if stats2.txt is loaded on (5) instead on
stats1.txt? I am trying to figure out if the Server will reject stats file
from a different timeline than the one its been rolled back to.
regards
Sameer

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