Subject | Re: [firebird-support] Re: What is the optimum pageSize? |
---|---|
Author | Mark Rotteveel |
Post date | 2019-11-15T07:33:42Z |
On 2019-11-14 23:47, blackfalconsoftware@... [firebird-support]
wrote:
exception of indexable items. The maximum keysize is slightly less than
1/4 of the page size. This means that with a page size of 4096, the max
you can index is +/- VARCHAR(1020) in a single byte character set or +/-
VARCHAR(256) UTF8 (I'm saying +/- here because exact size depends on
collations etc), while with page size 16384, the maximum is +/-
VARCHAR(4092) single byte character set / VARCHAR(1023) UTF8. That said,
trying to avoid such oversized indexes would be better: the more keys
fit on a single page, the more efficient the index.
With a larger page size, more records will fit on a single page (or very
wide records might fit on less pages). Page size can have influence on
performance, and generally larger page sizes are 'better' (although that
also depends on the underlying storage). However, if you use a lot of
relatively small blobs, you could be wasting more diskspace.
Mark
wrote:
> Doesn't the page size definition as per a database depend on oneThe page size doesn't restrict or limit your database design, with the
> designs their database tables and how such tables will be used?
exception of indexable items. The maximum keysize is slightly less than
1/4 of the page size. This means that with a page size of 4096, the max
you can index is +/- VARCHAR(1020) in a single byte character set or +/-
VARCHAR(256) UTF8 (I'm saying +/- here because exact size depends on
collations etc), while with page size 16384, the maximum is +/-
VARCHAR(4092) single byte character set / VARCHAR(1023) UTF8. That said,
trying to avoid such oversized indexes would be better: the more keys
fit on a single page, the more efficient the index.
With a larger page size, more records will fit on a single page (or very
wide records might fit on less pages). Page size can have influence on
performance, and generally larger page sizes are 'better' (although that
also depends on the underlying storage). However, if you use a lot of
relatively small blobs, you could be wasting more diskspace.
Mark