Обсуждение: how to find which tables required indexes in postgresql
hi,,
please suggest if there is any way which i can find which tables need indexes in postgresql.
please suggest if there is any way which i can find which tables need indexes in postgresql.
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hi,,
please suggest if there is any way which i can find which tables need indexes in postgresql.
Note,however,making excessive indexes may be harmful as well,so please be judicious while making them.
Regards,
Atri
Zahid Quadri, 10.04.2013 13:31: > hi,, > > please suggest if there is any way which i can find which tables need indexes in postgresql. > Tables don't need indexes. Queries do. You will need to show us the queries in question (e.g. those that are slow) in orderto decide which index is helpful. Thomas
Hello,
2013/4/10 Thomas Kellerer <spam_eater@gmx.net>
Zahid Quadri, 10.04.2013 13:31:hi,,
please suggest if there is any way which i can find which tables need indexes in postgresql.
You have some possibilities:
- the log file (slow queries)
- statistics with old information (see the ANALYZE command)
- statistics tables, for example: pg_stat_user_tables
You can run this SQL:
SELECT pg_stat_user_tables.schemaname,
pg_stat_user_tables.relname,
pg_stat_user_tables.seq_scan,
pg_stat_user_tables.seq_tup_read,
pg_stat_user_tables.idx_scan,
pg_stat_user_tables.idx_tup_fetch
FROM pg_stat_user_tables;
You can run this SQL:
SELECT pg_stat_user_tables.schemaname,
pg_stat_user_tables.relname,
pg_stat_user_tables.seq_scan,
pg_stat_user_tables.seq_tup_read,
pg_stat_user_tables.idx_scan,
pg_stat_user_tables.idx_tup_fetch
FROM pg_stat_user_tables;
If you have a big value in seq_scan column compared to the idx_scan column (small value), this indicate that you probably need to create an index in some column, but you need to discover what column needs the index. (the log file is a good indication).
Tables don't need indexes. Queries do. You will need to show us the queries in question (e.g. those that are slow) in order to decide which index is helpful.
Thomas
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Regards
On Wed, Apr 10, 2013 at 9:19 AM, JotaComm <jota.comm@gmail.com> wrote:
Hello,2013/4/10 Thomas Kellerer <spam_eater@gmx.net>Zahid Quadri, 10.04.2013 13:31:hi,,
please suggest if there is any way which i can find which tables need indexes in postgresql.You have some possibilities:- the log file (slow queries)- statistics with old information (see the ANALYZE command)- statistics tables, for example: pg_stat_user_tables
You can run this SQL:
SELECT pg_stat_user_tables.schemaname,
pg_stat_user_tables.relname,
pg_stat_user_tables.seq_scan,
pg_stat_user_tables.seq_tup_read,
pg_stat_user_tables.idx_scan,
pg_stat_user_tables.idx_tup_fetch
FROM pg_stat_user_tables;If you have a big value in seq_scan column compared to the idx_scan column (small value), this indicate that you probably need to create an index in some column, but you need to discover what column needs the index. (the log file is a good indication).
I'll also give a shout-out for pgBadger. It parses your slow query logs and creates a nice summary of queries that could use some attention.
On Wed, Apr 10, 2013 at 10:19 PM, JotaComm <jota.comm@gmail.com> wrote:
-- Hello,2013/4/10 Thomas Kellerer <spam_eater@gmx.net>Zahid Quadri, 10.04.2013 13:31:hi,,
please suggest if there is any way which i can find which tables need indexes in postgresql.You have some possibilities:- the log file (slow queries)- statistics with old information (see the ANALYZE command)- statistics tables, for example: pg_stat_user_tables
You can run this SQL:
SELECT pg_stat_user_tables.schemaname,
pg_stat_user_tables.relname,
pg_stat_user_tables.seq_scan,
pg_stat_user_tables.seq_tup_read,
pg_stat_user_tables.idx_scan,
pg_stat_user_tables.idx_tup_fetch
FROM pg_stat_user_tables;If you have a big value in seq_scan column compared to the idx_scan column (small value), this indicate that you probably need to create an index in some column, but you need to discover what column needs the index. (the log file is a good indication).
There is also this tool online that can help you to determine what are the slow parts of a query plan :
http://explain.depesz.com/
http://explain.depesz.com/
This is perhaps more simple than visualizing raw ANALYZE output, and it will help you to catch what are the tables needing indexing, or perhaps partial indexing.
Michael
On 04/10/2013 06:31 AM, Zahid Quadri wrote: > please suggest if there is any way which i can find which tables need > indexes in postgresql. If you have 8.4 or newer, you can look in pg_stat_statements for queries that use a lot of time. Check the where clauses for columns or transforms that can be indexed. Of course, you have to install it first. Take a look here: http://www.postgresql.org/docs/8.4/static/pgstatstatements.html -- Shaun Thomas OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604 312-676-8870 sthomas@optionshouse.com ______________________________________________ See http://www.peak6.com/email_disclaimer/ for terms and conditions related to this email