On Mon, Sep 12, 2016 at 7:30 AM, Akash Bedi <abedi0501@xxxxxxxxx> wrote:
Note that a VACUUM wouldn't be able to remove the dead rows if there's a long running active query OR any idle transaction in an isolation >= Repeatable Read, tracking transactions in "pg_stat_activity" should help you eliminate/track this activity. Also, the row estimates consider the size of your table, so it isn't necessary that close estimates indicate an ANALYZE operation performed, a better way to track this would be monitoring results from "pg_stat_user_tables", tracking when was did the autovacuum/analyze last performed on this tableRegards,AkashOn Mon, Sep 12, 2016 at 4:36 PM, Francisco Olarte <folarte@xxxxxxxxxxxxxx> wrote:Hi:
On Mon, Sep 12, 2016 at 1:17 AM, Patrick B <patrickbakerbr@xxxxxxxxx> wrote:
>> schemaname relname n_live_tup n_dead_tup
>> ---------- ------------- ---------- ----------
>> public parts 191623953 182477402
...
> Because of that the table is very slow...
> When I do a select on that table it doesn't use an index, for example:
> \d parts;
>> "index_parts_id" btree (company_id)
>> "index_parts_id_and_country" btree (company_id, country)
> explain select * from parts WHERE company_id = 12;
>> Seq Scan on parts (cost=0.00..6685241.40 rows=190478997 width=223)
>> Filter: (company_id = 12)
You've already been directed to check table is really getting vacuumed
/ analyzed, but I'd like to point that if the count estimates are
nearly correct that plan is good ( it's estimating getting more than
99% of the table, a seq scan tends to beat index scan easily when
selecting that big part of the table, even accounting for dead tuples
it's more about 50% of the table, and a seq scan is much faster PER
TUPLE then an index scan ( and and index scan would likely touch every
data page for that big fraction, so reading all of them sequentially
and oing a quick filter is easier )).
Francisco Olarte.
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Just out of curiosity, rather than rely on auto_vacuum, have you considered scheduling a cron job to do a manual vacuum / analyze in off peak hours?
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Melvin Davidson
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I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.
