Baron Schwartz wrote:
On Dec 20, 2007 7:16 AM, Sharon <[EMAIL PROTECTED]> wrote:
Baron Schwartz wrote:
Hi,
On Dec 20, 2007 2:15 AM, Sharon <[EMAIL PROTECTED]> wrote:
Hello all,
Given this table:
DROP TABLE IF EXISTS `maprimary`.`tbl_locales_ip2l`;
CREATE TABLE `maprimary`.`tbl_locales_ip2l` (
`ipStart` int(10) unsigned zerofill NOT NULL default '0000000000',
`ipEnd` int(10) unsigned zerofill NOT NULL default '0000000000',
`countryCode` varchar(2) default NULL,
`country` varchar(100) default NULL,
`state` varchar(100) default NULL,
`city` varchar(120) default NULL,
`lat` float NOT NULL default '0',
`lon` float NOT NULL default '0',
`zipCode` varchar(10) NOT NULL default '0',
`timeZone` int(10) NOT NULL default '0',
PRIMARY KEY USING BTREE (`ipStart`,`ipEnd`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;
When I use this query:
SELECT * FROM `tbl_locales_ip2l` WHERE `ipStart` <= 3741319167 AND
`ipEnd` >= 3741319167;
I can see that the primary key is not used and the query takes about 3 sec.
But when I use this query:
SELECT * FROM `tbl_locales_ip2l` WHERE `ipStart` <= 374131916 AND
`ipEnd` >= 374131916;
The primary key is used.
The table contains about 3M rows.
Can anyone explain?
Thanks, Sharon.
if the query will access more than a certain amount of rows, it won't
be used. There is a set of heuristics for this; the actual number
varies, but people often say a full scan is about as much work as an
index scan that retrieves 30% of the rows. That's not quite the way
the optimizer works, but it gives you an idea.
If you think it really will be faster, use USE INDEX or FORCE INDEX and see.
Baron
You're right, forcing the index results in a 47 sec. query.
Any idea how to optimize this table?
3 seconds query (not forcing the index) is way too slow.
Try InnoDB with the same primary key. This will cluster the rows
together physically and *might* be faster, but it depends on your
queries.
Side note: be careful of making the varchar columns larger than you
need, as any operations that use an in-memory temporary table (shown
by "Using temporary" in EXPLAIN) will use the full length of the
column, even if only a few characters are used. (The Memory storage
engine doesn't support variable-length rows).
9 sec. using InnoDB, 3 times slower.
By the way, the query will always return 1 row.
Thanks for the tip, I really need to cut those varchars.
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