Subject Re: [firebird-support] OLAP tuning in Firebird 2.1
Author Alexandre Benson Smith
Richard Wesley wrote:
> It takes roughly 4 seconds to table scan this data source so it
> appears that this is doing a table scan based on time versus
> retrieving the unique keys from the index. That makes sense to me when
> we include a measure, such as in the following, since computing the
> measure will require touching all the records. But in the above, we
> are only operating on the key of the index – why touch the data pages?

Because of MVCC indices on Firebird are dirty, the have no transactional
context, so the negine needs to go to the records (data pages) to see if
an index is visible or not to a given transaction.

There is no way to FB resolve a query just using the index information.

see you !

Alexandre Benson Smith
THOR Software e Comercial Ltda
Santo Andre - Sao Paulo - Brazil