Re: Postgres seems to use indexes in the wrong order - Mailing list pgsql-general

On Tue, Jan 27, 2015 at 6:59 AM, Tim Uckun <timuckun@gmail.com> wrote:

The query seems to first use the timestamp column which results in a huge number of records and then filters out using the integer and the macaddr indices.  If it was to use the integer index first it would start with a tiny number of records.

​May be the record distribution of quantiles is skewed.​ Have you tried to set more granular statistics for your int column?

The effective_cache_size is one gig. The others are not set so therefore the default.

​Ideally the effective_cache_size can be set to as much as 50-60% of your available memory. Also you need to tune your random_page_cost as per the behavior of your disk. 

https://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server​

​If these two does not work then may be you should go for setting a more granular statistics collection for your specific column-

alter table <table_name> alter column <column_Name> set  statistics 1000;

analyze <table_name>;

​

Best Regards,

Sameer Kumar | Database Consultant

ASHNIK PTE. LTD.

101 Cecil Street, #11-11 Tong Eng Building, Singapore 069533

M: +65 8110 0350  T: +65 6438 3504 | www.ashnik.com

 

 

This email may contain confidential, privileged or copyright material and is solely for the use of the intended recipient(s).