I am relying on reltuples on my web app to get fast row counts.
This was recommended by this article to get fast approx row counts:
https://wiki.postgresql.org/wiki/Count_estimate
However for some table I am getting twice as many values when I try to do
this. I did some more research and came up with this query.
select reltuples, n_live_tup, n_dead_tup
from pg_stat_user_tables join pg_class using (relname)
where relname =
'main_csv_0f247511f5c247c8813ba3cec90c6ae1_yf34fbb38d';
it returns
reltuples | n_live_tup | n_dead_tup
-------------+------------+------------
2.7209e+06 | 1360448 | 1360448
If I run analyze main_csv_0f247511f5c247c8813ba3cec90c6ae1_yf34fbb38d
and I run the same query again,
reltuples | n_live_tup | n_dead_tup
-------------+------------+------------
1.36045e+06 | 1360448 | 1360448
But after some time the value goes back to being double the value. This is
causing me a lot of problems since this inaccuracy does not make any sense
to me.
Any help would be appreciated.
FYI, also asked the same question on stackoverflow since I am new to
postgres mail lists.
https://stackoverflow.com/questions/49625259/postgres-reltuples-seems-to-return-twice-the-number-of-values
--
~Ranjith
