Speeding up MySQL update query

Make sure you have an index on table(id1, num).

Already done. I should have mentioned that..

I've tried setting them up seperately and jointly as you said (id1, num)... which did actually give me a speed boost from where I was before that point, but still leaves me at the problem described above.

Can you show us the results of:

SHOW CREATE TABLE table;

EXPLAIN SELECT * FROM table WHERE id1=10 AND num=20902 ;

Sure, to heck with innocent ... here is the show create table as it is actually being used.

idx   |CREATE TABLE `idx` (
`mlsnum` varchar(10) NOT NULL COMMENT 'mls number, semi-unique id for property
not mls',
`propclass` varchar(30) default NULL,
`proptype` varchar(30) default NULL,
  `propclass` varchar(30) default NULL,
  `proptype` varchar(30) default NULL,
  `askprice` int(10) default NULL,
  `showaddress` tinyint(1) default '1',
  `address` varchar(255) default NULL,
  `address2` varchar(255) default NULL,
  `city` varchar(50) default NULL,
  `state` char(3) default NULL,
  `zipcode` varchar(10) default NULL,
  `sqft` int(7) default NULL,
  `sqft1` varchar(30) default NULL,
  `numbdrms` int(2) default NULL,
  `numfullbath` int(2) default NULL,
  `numhalfbath` int(2) default NULL,
  `garage` varchar(30) default NULL,
  `basement` varchar(30) default NULL,
  `acres` float(8,2) default NULL,
  `listingoffice` varchar(255) default NULL,
  `listingofficephone` varchar(30) default NULL,
  `subdivsn` varchar(30) default NULL,
  `county` varchar(30) default NULL,
  `school` varchar(30) default NULL,
  `level1` char(1) default NULL,
  `dimensions1` varchar(14) default NULL,
  `level2` char(1) default NULL,
  `dimensions2` varchar(14) default NULL,
  `level3` char(1) default NULL,
  `dimensions3` varchar(14) default NULL,
  `level4` char(1) default NULL,
  `dimensions4` varchar(14) default NULL,
  `level5` char(1) default NULL,
  `dimensions5` varchar(14) default NULL,
  `level6` char(1) default NULL,
  `dimensions6` varchar(14) default NULL,
  `level7` char(1) default NULL,
  `dimensions7` varchar(14) default NULL,
  `level8` char(1) default NULL,
  `dimensions8` varchar(14) default NULL,
  `level9` char(1) default NULL,
  `dimensions9` varchar(14) default NULL,
  `level10` char(1) default NULL,
  `dimensions10` varchar(14) default NULL,
  `level11` char(1) default NULL,
  `dimensions11` varchar(11) default NULL,
  `roomname` varchar(13) default NULL,
  `numunits` int(3) default NULL,
  `unit1a` char(3) default NULL,
  `unit1b` char(3) default NULL,
  `unit1c` varchar(6) default NULL,
  `unit2a` char(3) default NULL,
  `unit2b` char(3) default NULL,
  `unit2c` varchar(6) default NULL,
  `unit3a` char(3) default NULL,
  `unit3b` char(3) default NULL,
  `unit3c` varchar(6) default NULL,
  `unit4a` char(3) default NULL,
  `unit4b` char(3) default NULL,
  `unit4c` varchar(6) default NULL,
  `surfacewater` tinyint(1) default NULL,
  `features` varchar(255) default NULL,
  `remarks` varchar(255) default NULL,
  `thumbnail` tinyint(1) default NULL,
  `thumbnailname` varchar(255) default NULL,
  `photopath` varchar(255) default NULL,
  `agencyid_fk` int(10) default NULL,
  `taxes` varchar(6) default NULL,
  `AgentName` varchar(16) default NULL,
  `yearbuilt` int(4) default NULL,
  `mlsid` int(8) NOT NULL default '0',
  PRIMARY KEY  (`mlsnum`,`mlsid`),
  UNIQUE KEY `mlsid` (`mlsnum`,`mlsid`),
  KEY `test` (`mlsid`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 |

Eplain coming in a few seconds....

+----+-------------+-------+------+--------------------+------+---------+-------+------+-------------+
| id | select_type | table | type | possible_keys      | key  | key_len | ref   | rows | Extra       |
+----+-------------+-------+------+--------------------+------+---------+-------+------+-------------+
|  1 | SIMPLE      | idx   | ref  | PRIMARY,mlsid,test | test | 4       | const | 1131 | Using where |
+----+-------------+-------+------+--------------------+------+---------+-------+------+-------------+
1 row in set (0.00 sec)

FYI, you don't need the UNIQUE KEY, since those columns are in the primary key (which is both unique and not null).

Try this:

EXPLAIN SELECT * FROM table IGNORE INDEX (test) WHERE id1=10 AND num=20902 ;

Ok, I noticed something there... that the select statement didn't even register time-wise. As I understand it, an update with the added overhead of a write... so I ran that particular update by itself and it ran in .06 seconds, which is an acceptable time.

So I am thinking that the problem must have somehting to do with having so many statements ran one after another?

RE: FYI, you don't need the UNIQUE KEY, since those columns are in the primary key (which is both unique and not null).

gotcha, what can I say... I've gotten desperate :)


mysql> EXPLAIN SELECT * FROM idx IGNORE INDEX (test) WHERE mlsid=10 AND mlsnum=20902 ;
+----+-------------+-------+------+---------------+------+---------+------+-------+-------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref  | rows  | Extra       |
+----+-------------+-------+------+---------------+------+---------+------+-------+-------------+
|  1 | SIMPLE      | idx   | ALL  | PRIMARY,mlsid | NULL | NULL    | NULL | 81219 | Using where |
+----+-------------+-------+------+---------------+------+---------+------+-------+-------------+
1 row in set (0.02 sec)

To give a better idea of what is going on here, all the sql statements are dumped into text files (currently about 10) and run with a batch file.

The largest text file has about 31 k statements in it, about 1 out of 5 similiar to the statement we have been discussing.

All that put aside... I ran the script again and it is moving much faster.

I guess I overworked the problem.

Thanks so much for your help!

or not ... it hit one of the big files and slowed down again .. and I was so excited I almost posted points :)

I think the statements made before were for some of the update statements that apperently run much faster..

Take a look at this:


mysql> EXPLAIN SELECT * FROM idx IGNORE INDEX (test) WHERE mlsid=22 AND mlsnum=436306 ;
+----+-------------+-------+------+---------------+------+---------+------+-------+-------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref  | rows  | Extra       |
+----+-------------+-------+------+---------------+------+---------+------+-------+-------------+
|  1 | SIMPLE      | idx   | ALL  | PRIMARY,mlsid | NULL | NULL    | NULL | 81219 | Using where |
+----+-------------+-------+------+---------------+------+---------+------+-------+-------------+
1 row in set (0.28 sec)

mysql> EXPLAIN SELECT * FROM idx IGNORE INDEX (test) WHERE mlsid=22 AND mlsnum=436306 ;
+----+-------------+-------+------+---------------+------+---------+------+-------+-------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref  | rows  | Extra       |
+----+-------------+-------+------+---------------+------+---------+------+-------+-------------+
|  1 | SIMPLE      | idx   | ALL  | PRIMARY,mlsid | NULL | NULL    | NULL | 81219 | Using where |
+----+-------------+-------+------+---------------+------+---------+------+-------+-------------+
1 row in set (1.63 sec)

mysql> EXPLAIN SELECT * FROM idx IGNORE INDEX (test) WHERE mlsid=22 AND mlsnum=436306 ;
+----+-------------+-------+------+---------------+------+---------+------+-------+-------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref  | rows  | Extra       |
+----+-------------+-------+------+---------------+------+---------+------+-------+-------------+
|  1 | SIMPLE      | idx   | ALL  | PRIMARY,mlsid | NULL | NULL    | NULL | 81219 | Using where |
+----+-------------+-------+------+---------------+------+---------+------+-------+-------------+
1 row in set (1.89 sec)


Things are still much too slow... still need some help here.

I think that perhaps the reason it is not using the index is that your mlsnum column is defined as VARCHAR, but you're passing in a number, which MySQL converts to a VARCHAR internally.  Try this:

EXPLAIN SELECT * FROM idx IGNORE INDEX (test) WHERE mlsid=22 AND mlsnum='436306' ;

mysql> EXPLAIN SELECT * FROM idx IGNORE INDEX (test) WHERE mlsid=22 AND mlsnum='436306' ;
+----+-------------+-------+------+----------------------+---------+---------+-------------+------+-------------+
| id | select_type | table | type | possible_keys        | key     | key_len | ref         | rows | Extra       |
+----+-------------+-------+------+----------------------+---------+---------+-------------+------+-------------+
|  1 | SIMPLE      | idx   | ref  | PRIMARY,mlsid,mlsnum | PRIMARY | 16      | const,const |    1 | Using where |
+----+-------------+-------+------+----------------------+---------+---------+-------------+------+-------------+
1 row in set (0.42 sec)



When repeated the it ranges in time between .17 and .95 sec

That did it... much better!

Anything else you can think of that might speed things up?

If the mlsnum really is a numeric value, I would redefine the column as such and revert to the original update statement.  Comparisons using numeric values as opposed to text will be faster, but probably not by a significant measure.

gotcha.. can't depend on it to be numeric in any case, alpha-numerics pop up every once in awhile.


The answers you already gave have taken care of the major blockage that caused me to post. So thnx a million:)

If you can come up with anything else that may help it more, I'll be glad to send over some more points.