[Info-Ingres] Lock escalation caused by bad page estimate

[Martin Bowes]

Hi Karl,
 
And what does an F stand for? Be nice. Would it be an overflow on an index leaf?
 
Marty

________________________________

From: info-ingres-bounces at kettleriverconsulting.com on behalf of Betty & Karl Schendel
Sent: Fri 21/09/2007 12:04
To: info-ingres at kettleriverconsulting.com
Subject: Re: [Info-Ingres] Lock escalation caused by bad page estimate



At 11:52 AM +0100 9/21/07, Martin Bowes wrote:
>...
>I tried a modify table to table_debug with table_option=2 and
>counted 116 pages (ie. a lot more than 40) flagged with either a D
>or an A. I also examined the tids in the table to check for page
>number and came up with 116 distinct values. The sequence of page
>numbers and D's and A's matches as well.
>
>I don't know what an 'A' page is - they clearly have data on them - any ideas?
>

A is an Associated data page, ie the data page currently being used
for row inserts from a leaf.  The data page is associated to that leaf,
hence the name.

>But of course the optimiser is a *LOT* smarter than I am. It
>realised that the query didn't rely on data just on keys, so it only
>need to scan the L pages holding the Key details to do the outer
>join. And guess what - theres 40 of them, and those are the pages
>that the lock trace show are being opened.

Nice catch, I was wondering where the 40 came from.  Didn't
think of leaf-only scans.

Karl
_______________________________________________
Info-Ingres mailing list
Info-Ingres at kettleriverconsulting.com
http://www.kettleriverconsulting.com/mailman/listinfo/info-ingres


-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.kettleriverconsulting.com/mailman/private/info-ingres/attachments/20070921/217a804e/attachment.html