On 01/19/2011 02:32 PM, Sergey Petrunya wrote:
> Hello,
>
> index_merge uses @@sort_buffer_size as a guide of how much space it can use
> for
> sorting. I think there is an issue with the way it is done.
>
> Before index_merge was introduced, @@sort_buffer_size was used only by
> filesort (also
Hello,
index_merge uses @@sort_buffer_size as a guide of how much space it can use for
sorting. I think there is an issue with the way it is done.
Before index_merge was introduced, @@sort_buffer_size was used only by
filesort (also for couple of other cases like GROUP_CONCAT with sorting, but I
Hi, Lichao!
On Jan 10, Lichao Xie wrote:
> hi all:
> I have a question about the optimization of count(*) in a range.
> Sql for mysql like:select count(*) from t where id > 10 and id < 100;
> In table t, there is an B-tree index on id field, this sql will read
> hundreds of thousands of record
Another question: why is type='range' for sort_intersect? We have
type=index_merge for intersect and [sort]_union, so it seems rather confusing
that we have type=range for sort_intersect?
- Forwarded message from Sergey Petrunya -
Date: Wed, 19 Jan 2011 11:11:14 +0300
From: Sergey Petru
Hello Igor,
I was looking at sort-intersect and noticed the following: Consider this table:
CREATE TABLE `t1` (
`k1` int(11) DEFAULT NULL,
`k2` int(11) DEFAULT NULL,
`filler` char(100) DEFAULT NULL,
KEY `k1` (`k1`),
KEY `k2` (`k2`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
Let's try
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