Re: ANALYZE Command

From: Connor McDonald <connor_mcdonald_at_yahoo.com>
Date: Thu, 01 Jul 1999 23:05:38 +0800
Message-ID: <377B83C2.70D3@yahoo.com>

flowerss_at_my-deja.com wrote:
>
> I've just started performance tuning a database
> and I don't understand the logic of the ANALYZE
> command. I ran the command; however, I don't
> understand how to make use of it. Specifically,
> the Endpoint_Number and Endpoint_Value Field?
>
> Please help.
>
> Thanks,
> Selena
>
> Sent via Deja.com http://www.deja.com/
> Share what you know. Learn what you don't.

"You" don't make use of it - the optimiser does...

An SQL gets presented to the database - it tries to make decisions on how best to run it ... using analyze arms the database with more information on the best way to go...

The optimiser will range from simple stuff like "ooh that table is huge, I'll try stay away from scanning that one" to looking at column densities to determine index and filtering options in where clauses...

Your "endpoints" concern histograms which can be useful when:

1. your database distribution on a column(s) is skewed
2. you query based on values in these columns
3. you query using static (as opposed to bind variables) on these columns...

HTH
--

---

Connor McDonald
"These views mine, no-one elses etc etc" connor_mcdonald_at_yahoo.com

"Some days you're the pigeon, and some days you're the statue." Received on Thu Jul 01 1999 - 10:05:38 CDT