| Subject | Re: [firebird-support] Re: Why does Firebird write so much data for simple select queries? |
|---|---|
| Author | Ann Harrison |
| Post date | 2011-10-28T16:05:11Z |
On Fri, Oct 28, 2011 at 2:36 AM, ma_golyo <ma_golyo@...> wrote:
for sort buffers in the configuration, nothing will be written. GROUP BY
and DISTINCT also sort and have the same behavior.
Actually there's another case. When the sort can be emulated by walking the
index, nothing will be written to disk.
Good luck,
Ann
[Non-text portions of this message have been removed]
>Not necessarily. If the data to be sorted can fit in the memory specified
> "Firebird doesn't write anything to disk for a Select,..."
>
> That's not true. Firebird writes the resultset on HDD when SELECT contains
> ORDER BY (maybe PLAN SORT affect that), and does the ordering in this file.
>
for sort buffers in the configuration, nothing will be written. GROUP BY
and DISTINCT also sort and have the same behavior.
Actually there's another case. When the sort can be emulated by walking the
index, nothing will be written to disk.
Good luck,
Ann
[Non-text portions of this message have been removed]