Re: Schema design question as it pertains to performance

Thanks for the clarification. Now I understand - it is an all or nothing due to required entries for each row version on the main table.
I will have to see if removing the constantly changing value from the indices will affect the performance of our selects.

-----Original Message-----
From: Kevin Grittner [mailto:kgrittn(at)mail(dot)com]
Sent: Tuesday, January 22, 2013 5:23 PM
To: Benjamin Krajmalnik; pgsql-admin(at)postgresql(dot)org
Subject: RE: [ADMIN] Schema design question as it pertains to performance

Benjamin Krajmalnik wrote:
> Kevin Grittner wrote:
>> Benjamin Krajmalnik wrote:

>>> I also assume that if no data has changed in an index, nothing is
>>> done when the record is updated as pertains to the particular index
>>> - am I correct in this assumption?
>>
>> No. [...] If any indexed column is updated, [...] it needs new
>> entries in all the indexes.

> That was my intent - if no column of an index changes in an update
> then no changes are done on the index.

I don't think you understood -- if any column referenced by any index is updated, then all indexes must get a new entry for that row whether or not they include that column. The new version of the row will be at a new location, so new entries are needed in all indexes to point to the new location.

I did *not* say that only indexes referencing the updated column need a new entry.

-Kevin