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From David Parker <...@tractionsoftware.com>
Subject Re: pagesize for a given table
Date Tue, 02 Feb 2010 15:01:28 GMT
Thanks, that's good to know.

We have a high rate of inserts into this wide table - page access statistics. In the field
we have customers who have experienced
slowdowns that we have traced to this insert - a single insert taking several seconds, long
enough to make it unusable as part 
of the site.

Unfortunately we are not able to repro the issue in-house, so I'm just trying to put together
as many diagnostics as I can, and I'm new to derby. So I appreciate everybody's assistance!

- DAP

On Feb 2, 2010, at 9:49 AM, Bryan Pendleton wrote:

> Hi David,
> 
>> At what point does derby decide on the pagesize when it is creating a table?
> 
> During the bind processing (compilation) of the CREATE TABLE statement itself.
> 
>> I have a table with several varchar(4000) fields in it. Though they are 
> > varchar, does derby calculate row size based on the maximum possible column
> > size for variable sized columns in deciding whether to bump up the pagesize to 32K?
> 
> Yes, Derby bases its calculation on the max column size for VARCHAR, so 4000
> in your case.
> 
> I'm a little surprised that the too-large pagesize would adversely affect
> your performance, but you should be able to test it yourself by setting
> the derby.storage.pageSize property, as Derby will obey that property even
> if you have multiple long VARCHAR columns in your table.
> 
> thanks,
> 
> bryan
> 
> 

=============================================
David Parker
dap@tractionsoftware.com





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