Re: [PERFORM] help with dual indexing

2004-01-26 Thread Orion Henry
Thanks Tom!  You're a life-saver.

On Fri, 2004-01-23 at 17:08, Tom Lane wrote:
> Orion Henry <[EMAIL PROTECTED]> writes:
> > The queries usually are in the form of, where "user_id = something and
> > event_time between something and something".
> 
> > Half of my queries index off of the user_id and half index off the
> > event_time.  I was thinking this would be a perfect opportunity to use a
> > dual index of (user_id,event_time) but I'm confused as to weather this
> > will help
> 
> Probably.  Put the user_id as the first column of the index --- if you
> think about the sort ordering of a multicolumn index, you will see why.
> With user_id first, a constraint as above describes a contiguous
> subrange of the index; with event_time first it does not.
> 
>   regards, tom lane
-- 
Orion Henry <[EMAIL PROTECTED]>


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Re: [PERFORM] help with dual indexing

2004-01-23 Thread Tom Lane
Orion Henry <[EMAIL PROTECTED]> writes:
> The queries usually are in the form of, where "user_id = something and
> event_time between something and something".

> Half of my queries index off of the user_id and half index off the
> event_time.  I was thinking this would be a perfect opportunity to use a
> dual index of (user_id,event_time) but I'm confused as to weather this
> will help

Probably.  Put the user_id as the first column of the index --- if you
think about the sort ordering of a multicolumn index, you will see why.
With user_id first, a constraint as above describes a contiguous
subrange of the index; with event_time first it does not.

regards, tom lane

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