Re: n_live_tup number double after migration do PG 10.4

Hi,
The query I’m talking about is
SELECT schemaname, relname, sum(n_live_tup) AS n_live_tup, sum(n_dead_tup) AS n_dead_tup
FROM pg_stat_user_tables
GROUP BY schemaname, relname
ORDER BY n_live_tup DESC;

> Le 6 août 2018 à 06:24, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> a écrit :
>
> Keith <keith(at)keithf4(dot)com> writes:
>> On Sun, Aug 5, 2018 at 5:29 AM, Mai Peng <maily(dot)peng(at)webedia-group(dot)com>
>> wrote:
>>> After the migration to pg 10 by pg_upgrade and vacuumdb, I’ve seen the
>>> number of live tuple double and performance decreases on few queries.
>
>> The value stored in n_liv_tup is the value seen when the last analyze was
>> run on the table.
>
> No, you're confusing this with pg_class.reltuples. I think the OP is
> talking about pg_stat counters such as pg_stat_all_tables.n_live_tup.
> Those should update after every transaction, although there are various
> reasons why they might be inaccurate.
>
> The OP hasn't given us nearly enough information to speculate usefully
> on what he's seeing. I'd suggest reading
>
> https://wiki.postgresql.org/wiki/Guide_to_reporting_problems
>
> regards, tom lane