MySQL not using the correct index
I have following readings table, it has around 500 million rows.
CREATE TABLE readings (
id int(11) NOT NULL AUTO_INCREMENT,
value double NOT NULL,
created_dt datetime NOT NULL,
device_id int(11) NOT NULL,
PRIMARY KEY (id),
UNIQUE KEY readings_created_dt_483d31a3654ede43_uniq (created_dt,device_id),
KEY readings_device_id_6a03c4ab761154d1_fk_device_id (device_id),
CONSTRAINT readings_device_id_6a03c4ab761154d1_fk_device_id FOREIGN KEY (device_id) REFERENCES device (id)
) ENGINE=InnoDB AUTO_INCREMENT=138611438 DEFAULT CHARSET=latin1
It has an index on (created_dt, device_id) and an index on device_id( which is foreign key)
When i run following query
SELECT value, created_dt FROM readings WHERE (created_dt BETWEEN '2019-03-17 19:11:00' AND '2019-03-18 19:11:00' AND (device_id) IN (10, 11, 12));
Above query takes around 2 minutes.
DESCRIBE query returns the index used is 'readings_device_id_6a03c4ab761154d1_fk_device_id' which is foreign key index on device_id. However if i remove the above index and run the query again, it uses 'readings_created_dt_483d31a3654ede43_uniq' which is an index on both (created_dt, device_id) and retuns data in less than a second.
mysql
asked 4 mins ago
AndroAndro
1
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I have following readings table, it has around 500 million rows.
CREATE TABLE readings (
id int(11) NOT NULL AUTO_INCREMENT,
value double NOT NULL,
created_dt datetime NOT NULL,
device_id int(11) NOT NULL,
PRIMARY KEY (id),
UNIQUE KEY readings_created_dt_483d31a3654ede43_uniq (created_dt,device_id),
KEY readings_device_id_6a03c4ab761154d1_fk_device_id (device_id),
CONSTRAINT readings_device_id_6a03c4ab761154d1_fk_device_id FOREIGN KEY (device_id) REFERENCES device (id)
) ENGINE=InnoDB AUTO_INCREMENT=138611438 DEFAULT CHARSET=latin1
It has an index on (created_dt, device_id) and an index on device_id( which is foreign key)
When i run following query
SELECT value, created_dt FROM readings WHERE (created_dt BETWEEN '2019-03-17 19:11:00' AND '2019-03-18 19:11:00' AND (device_id) IN (10, 11, 12));
Above query takes around 2 minutes.
DESCRIBE query returns the index used is 'readings_device_id_6a03c4ab761154d1_fk_device_id' which is foreign key index on device_id. However if i remove the above index and run the query again, it uses 'readings_created_dt_483d31a3654ede43_uniq' which is an index on both (created_dt, device_id) and retuns data in less than a second.
mysql
asked 4 mins ago
AndroAndro
1
New contributor
Andro is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
I have following readings table, it has around 500 million rows.
CREATE TABLE readings (
id int(11) NOT NULL AUTO_INCREMENT,
value double NOT NULL,
created_dt datetime NOT NULL,
device_id int(11) NOT NULL,
PRIMARY KEY (id),
UNIQUE KEY readings_created_dt_483d31a3654ede43_uniq (created_dt,device_id),
KEY readings_device_id_6a03c4ab761154d1_fk_device_id (device_id),
CONSTRAINT readings_device_id_6a03c4ab761154d1_fk_device_id FOREIGN KEY (device_id) REFERENCES device (id)
) ENGINE=InnoDB AUTO_INCREMENT=138611438 DEFAULT CHARSET=latin1
It has an index on (created_dt, device_id) and an index on device_id( which is foreign key)
When i run following query
SELECT value, created_dt FROM readings WHERE (created_dt BETWEEN '2019-03-17 19:11:00' AND '2019-03-18 19:11:00' AND (device_id) IN (10, 11, 12));
Above query takes around 2 minutes.
DESCRIBE query returns the index used is 'readings_device_id_6a03c4ab761154d1_fk_device_id' which is foreign key index on device_id. However if i remove the above index and run the query again, it uses 'readings_created_dt_483d31a3654ede43_uniq' which is an index on both (created_dt, device_id) and retuns data in less than a second.
mysql
asked 4 mins ago
AndroAndro
1
New contributor
Andro is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I have following readings table, it has around 500 million rows.
CREATE TABLE readings (
id int(11) NOT NULL AUTO_INCREMENT,
value double NOT NULL,
created_dt datetime NOT NULL,
device_id int(11) NOT NULL,
PRIMARY KEY (id),
UNIQUE KEY readings_created_dt_483d31a3654ede43_uniq (created_dt,device_id),
KEY readings_device_id_6a03c4ab761154d1_fk_device_id (device_id),
CONSTRAINT readings_device_id_6a03c4ab761154d1_fk_device_id FOREIGN KEY (device_id) REFERENCES device (id)
) ENGINE=InnoDB AUTO_INCREMENT=138611438 DEFAULT CHARSET=latin1
It has an index on (created_dt, device_id) and an index on device_id( which is foreign key)
When i run following query
SELECT value, created_dt FROM readings WHERE (created_dt BETWEEN '2019-03-17 19:11:00' AND '2019-03-18 19:11:00' AND (device_id) IN (10, 11, 12));
Above query takes around 2 minutes.
DESCRIBE query returns the index used is 'readings_device_id_6a03c4ab761154d1_fk_device_id' which is foreign key index on device_id. However if i remove the above index and run the query again, it uses 'readings_created_dt_483d31a3654ede43_uniq' which is an index on both (created_dt, device_id) and retuns data in less than a second.
mysql
mysql
asked 4 mins ago
AndroAndro
1
New contributor
Andro is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 mins ago
AndroAndro
1
New contributor
Andro is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 mins ago
AndroAndro
1
New contributor
Andro is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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asked 4 mins ago
AndroAndro
1
asked 4 mins ago
AndroAndro
1
1
New contributor
Andro is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Andro is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
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