Subject | Fw: Performance |
---|---|
Author | Leyne, Sean |
Post date | 2003-06-23T16:41:48Z |
In a message on the Borland b.p.i.general newsgroup "Jason Chapman
(JAC2)" <jason@...> wrote...
Does the engine really unpack blobs which are not part of the select
criteria?
Sean
(JAC2)" <jason@...> wrote...
> I would use a blob or a separate table. You must consider whathappens when
> your query doe not use an index to locate all records required, e.g.select
> * from myTable where thedate between xxxx and yyyy and someData =1all
> where someData does not have an index. The engine will have to unpack
> of the records that fit into the date criteria into RAM and thentraverse
> them to see if somedata =1. I don't know how IB manages unpackeingrecords
> from disk to RAM, but I wouldn't be surprised if it uses buffers thatare
> full width of the rows for speed. If this is the case, then you willsee a
> massive performance hit.My question is:
Does the engine really unpack blobs which are not part of the select
criteria?
Sean