Re: Slow Query - PostgreSQL 9.2

On 1/10/16, Saulo Merlo <smerlo50(at)outlook(dot)com> wrote:
> CREATE INDEX CONCURRENTLY index_name ON gorfs.inode_segments(st_ctime);
> ERROR: column "st_ctime" does not exist
> Look the error I've got
>
> Lucas
>
>> Date: Sun, 10 Jan 2016 22:43:21 -0800
>> Subject: Re: [GENERAL] Slow Query - PostgreSQL 9.2
>> From: vitaly(dot)burovoy(at)gmail(dot)com
>> To: smerlo50(at)outlook(dot)com
>> CC: pgsql-general(at)postgresql(dot)org
>>
>> On 1/10/16, Saulo Merlo <smerlo50(at)outlook(dot)com> wrote:
>> > Hi Vitaly,
>> >
>> > Yep... gorfs.nodes is a view.
>> > And the schema is: gorfs.inode_segments
>> > So... CREATE INDEX index_name ON gorfs.inode_segments(st_ctime)
>> > Is that correct? It would be "st_ctime"?
>> If "inodes" is an alias for "gorfs.inode_segments" in your view, yes,
>> the above DDL is OK. According to EXPLAIN's "Filter" row the column
>> involving in comparison is st_ctime.
>>
>> Hint: you can create the index without blocking table using "CREATE
>> INDEX CONCURRENTLY":
>> http://www.postgresql.org/docs/9.2/static/sql-createindex.html
>>
>> > I've rewriten the query as well. Thank you for that!
>> >
>> > Thank you
>> > Lucas
>>
>> >> Date: Sun, 10 Jan 2016 21:23:01 -0800
>> >> Subject: Re: [GENERAL] Slow Query - PostgreSQL 9.2
>> >> From: vitaly(dot)burovoy(at)gmail(dot)com
>> >> To: smerlo50(at)outlook(dot)com
>> >> CC: pgsql-general(at)postgresql(dot)org
>> >>
>> >> On 1/10/16, Vitaly Burovoy <vitaly(dot)burovoy(at)gmail(dot)com> wrote:
>> >> > On 1/10/16, Saulo Merlo <smerlo50(at)outlook(dot)com> wrote:
>> >> >> I've got a slow query.. I'd like to make it faster.. Make add an
>> >> >> index?
>> >> >> Query:
>> >> >> SELECT
>> >> >> <<overquoting>>
>> >> >> FROM gorfs.nodes AS f
>> >> >> <<overquoting>>
>> >> >> WHERE f.file_data IS NOT NULL
>> >> >> AND ((transaction_timestamp() AT TIME ZONE 'UTC') >
>> >> >> (f.last_changed
>> >> >> +
>> >> >> '24
>> >> >> months' :: INTERVAL)) LIMIT 100;
>> >> >
>> >> >> <<overquoting>>
>> >> >> "Total runtime: 94989.208 ms"What could I do to make it faster?
>> >> >> Thank
>> >> >> you.
>> >> >
>> >> > At least you can add an index:
>> >> > CREATE INDEX ON gorfs.nodes(last_changed)
>> >> >
>> >> > and rewrite part of WHERE clause to:
>> >> > (f.last_changed < (transaction_timestamp() AT TIME ZONE 'UTC' - '24
>> >> > months'::INTERVAL))
>> >> >
>> >> > It allows to decrease the slowest part of your query (sequence
>> >> > scanning of a table, all 13.5M rows):
>> >> >> -> Seq Scan on "inodes" "t" (cost=0.00..1411147.24 rows=13416537
>> >> >> width=29) (actual time=94987.224..94987.224 rows=0 loops=1)
>> >> >> Filter: ("timezone"('UTC'::"text", "transaction_timestamp"())
>> >> >> >
>> >> >> (("st_ctime")::timestamp without time zone + '2 years'::interval))
>> >> >
>> >> > compare that time to the one in the topmost row of EXPLAIN:
>> >> >> Limit (cost=1556.99..1336437.30 rows=100 width=186) (actual
>> >> >> time=94987.261..94987.261 rows=0 loops=1)
>> >>
>> >> Hmm. It seems that gorfs.nodes is a view.
>> >> So creating index should be something like (I have no idea that schema
>> >> name for it):
>> >> CREATE INDEX ON _schema_name_.inodes(st_ctime)

Please, post a definition of a table and a view (and all intermediate
views if any).

Via psql it can be done via:
\d gorfs.inode_segments
\d+ gorfs.nodes

--
Best regards,
Vitaly Burovoy