Re: Slow index scan on B-Tree index over timestamp field

[Igor Neyman <ineyman@xxxxxxxxxxxxxx>]

 

 

From: Caio Casimiro [mailto:casimiro.listas@xxxxxxxxx]
Sent: Monday, November 04, 2013 4:33 PM
To: Igor Neyman
Cc: Jeff Janes; pgsql-performance@xxxxxxxxxxxxxx
Subject: Re: Slow index scan on B-Tree index over timestamp field

 

These are the parameters I have set in postgresql.conf:

 

work_mem = 128MB

shared_buffers = 1GB

maintenance_work_mem = 1536MB

fsync = off

synchronous_commit = off

effective_cache_size = 2GB

 

The hardware is a modest one:

CPU: Intel(R) Atom(TM) CPU  230   @ 1.60GHz

RAM: 2GB

HD: 1TV 7200 RPM (WDC WD10EZEX-00RKKA0)

 

This machine runs a slackware 14.0 dedicated to the Postgresql. 

 

Thank you,

Caio

With just 2GB RAM, this:

 

shared_buffers = 1GB

 

and this:

 

effective_cache_size = 2GB

 

is too high.

 

You should lower those:

 

shared_buffers = 256MB

effective_cache_size = 1GB

 

and see how your execution plan changes.

 

Oh, and this:

maintenance_work_mem = 1536MB

 

is also too high.

Turning off fsync and synchronous_commit is not very good idea.

 

Regards,

Igor Neyman