Hello,
On Fri, Dec 05, 2003 at 12:02:05PM +0100, Martin Gillstr?m wrote:
>
> The table can look something like this:
> row_id INT PRIMARY KEY
> where_column SET('a','b','c')
> groupby_column VARCHAR(255)
> orderby_column DATE
> .. more rows that I need to fetch with the select.
> This is what I have tried but not seen any dramaticly speed improvements
> with:
> I have tried but I can't get mysql to use one index only.
> A also get that mysql uses temp tables and also store them disk. I have
> raised tmp_table_size without any success.
> I have experimented with sort_buffer_size, read_rnd_buffer_size,
> key_buffer_size.
As I understand it, you can't get MySQL to use an index for sorting
and grouping if you're sorting and grouping on a different row. This
one bites me too, and forces me to live with a "using temporary; using
filesort" query on one of my biggest busiest tables.
--
Chris
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