Subject Re: [firebird-support] Re: Page size
Author Ann W. Harrison
Eduardo A. Salgado wrote:
>
> I say use 4k as the basis and then forget about the page size until
> the depth of indexes becomes greater than 3 (whatever that means).

That's good advice. Get your data loaded using a 4Kb page then run
gstat on it with the -a and -r switches, sending the output to a file.

For each table, check the average record length. If you have any
records that average more than 2Kb, you should probably increase the
page size because one record per page isn't very efficient.

Check the indexes looking for any that have more than three levels.
Firebird indexes are shaped like triangles with a broad level at the
bottom containing key values and pointer to records, a much narrower
level above containing key values and pointers to the bottom pages,
and (one hopes) a single block at the top, containing key values and
pointers to pages of pointers to pages of pointers to records. After
four levels, you're spending more time getting through the pages of
pointers than is efficient. Doubling the page size quadruples the
fan-out...


Regards,


Ann