Re: slow query - will CLUSTER help?

On Thu, Dec 12, 2013 at 9:30 AM, Sev Zaslavsky <sevzas@gmail.com> wrote:
[...]

> Table rt_h_nbbo contains several hundred million rows.  All rows for a given
> entry_date are appended to this table in an overnight process every night -
> on the order of several million rows per day.

[...]

> I perceive an inefficiency here and I'd like your input as to how to deal
> with it: The end result of the query is 1631 rows which is on the order of
> about a couple hundred Kb of data.  Compare that to the amount of I/O that
> was done: 1634 buffers were loaded, 16Mb per page - that's about 24 Gb of
> data!  Query completed in 21 sec.  I'd like to be able to physically
> re-organize the data on disk so that the data for a given product_id on a
> entry_date is concentrated on a few pages instead of being scattered like I
> see here.

Do you perform a regular cleaning of the table with DELETEs or may be
you use UPDATEs for some another reason?

--
Kind regards,
Sergey Konoplev
PostgreSQL Consultant and DBA

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