Adding where condition with index make query slower(use filesort and temporary)
0
I'm trying to implement soft-delete so I added deleted_at (datetime) column to users table.
Also there is a query i need to run:
SELECT
COUNT(*) AS count_all,
`users`.`category_id` AS users_category_id
FROM
`users`
GROUP BY `users`.`category_id`;
type, possible_keys, key, key_len, ref, rows, filtered, Extra
'index', 'index_users_on_category_id', 'index_users_on_category_id', '5', NULL, '840926', '100.00', 'Using index'
which was running just fine until i added WHERE clause
SELECT
COUNT(*) AS count_all,
`users`.`category_id` AS users_category_id
FROM
`users`
WHERE
`users`.`deleted_at` IS NULL
GROUP BY `users`.`category_id`;
type, possible_keys, key, key_len, ref, rows, filtered, Extra
'ref', 'index_users_on_category_id,index_users_on_deleted_at', 'index_users_on_deleted_at', '6', 'const', '420463', '100.00', 'Using index condition; Using temporary; Using filesort'
Of course it becomes slower, i can't find information
- why type changed
- why key_len changed from 5 to 6
- why rows in second query shows half of total number (800k)
And how can i make it faster without using USE INDEX (index_users_on_category_id)
mysql-5.7
asked 2 mins ago
Alexandr ClimovAlexandr Climov
1
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Alexandr Climov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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0
I'm trying to implement soft-delete so I added deleted_at (datetime) column to users table.
Also there is a query i need to run:
SELECT
COUNT(*) AS count_all,
`users`.`category_id` AS users_category_id
FROM
`users`
GROUP BY `users`.`category_id`;
type, possible_keys, key, key_len, ref, rows, filtered, Extra
'index', 'index_users_on_category_id', 'index_users_on_category_id', '5', NULL, '840926', '100.00', 'Using index'
which was running just fine until i added WHERE clause
SELECT
COUNT(*) AS count_all,
`users`.`category_id` AS users_category_id
FROM
`users`
WHERE
`users`.`deleted_at` IS NULL
GROUP BY `users`.`category_id`;
type, possible_keys, key, key_len, ref, rows, filtered, Extra
'ref', 'index_users_on_category_id,index_users_on_deleted_at', 'index_users_on_deleted_at', '6', 'const', '420463', '100.00', 'Using index condition; Using temporary; Using filesort'
Of course it becomes slower, i can't find information
- why type changed
- why key_len changed from 5 to 6
- why rows in second query shows half of total number (800k)
And how can i make it faster without using USE INDEX (index_users_on_category_id)
mysql-5.7
asked 2 mins ago
Alexandr ClimovAlexandr Climov
1
New contributor
Alexandr Climov 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 |
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0
I'm trying to implement soft-delete so I added deleted_at (datetime) column to users table.
Also there is a query i need to run:
SELECT
COUNT(*) AS count_all,
`users`.`category_id` AS users_category_id
FROM
`users`
GROUP BY `users`.`category_id`;
type, possible_keys, key, key_len, ref, rows, filtered, Extra
'index', 'index_users_on_category_id', 'index_users_on_category_id', '5', NULL, '840926', '100.00', 'Using index'
which was running just fine until i added WHERE clause
SELECT
COUNT(*) AS count_all,
`users`.`category_id` AS users_category_id
FROM
`users`
WHERE
`users`.`deleted_at` IS NULL
GROUP BY `users`.`category_id`;
type, possible_keys, key, key_len, ref, rows, filtered, Extra
'ref', 'index_users_on_category_id,index_users_on_deleted_at', 'index_users_on_deleted_at', '6', 'const', '420463', '100.00', 'Using index condition; Using temporary; Using filesort'
Of course it becomes slower, i can't find information
- why type changed
- why key_len changed from 5 to 6
- why rows in second query shows half of total number (800k)
And how can i make it faster without using USE INDEX (index_users_on_category_id)
mysql-5.7
asked 2 mins ago
Alexandr ClimovAlexandr Climov
1
New contributor
Alexandr Climov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I'm trying to implement soft-delete so I added deleted_at (datetime) column to users table.
Also there is a query i need to run:
SELECT
COUNT(*) AS count_all,
`users`.`category_id` AS users_category_id
FROM
`users`
GROUP BY `users`.`category_id`;
type, possible_keys, key, key_len, ref, rows, filtered, Extra
'index', 'index_users_on_category_id', 'index_users_on_category_id', '5', NULL, '840926', '100.00', 'Using index'
which was running just fine until i added WHERE clause
SELECT
COUNT(*) AS count_all,
`users`.`category_id` AS users_category_id
FROM
`users`
WHERE
`users`.`deleted_at` IS NULL
GROUP BY `users`.`category_id`;
type, possible_keys, key, key_len, ref, rows, filtered, Extra
'ref', 'index_users_on_category_id,index_users_on_deleted_at', 'index_users_on_deleted_at', '6', 'const', '420463', '100.00', 'Using index condition; Using temporary; Using filesort'
Of course it becomes slower, i can't find information
- why type changed
- why key_len changed from 5 to 6
- why rows in second query shows half of total number (800k)
And how can i make it faster without using USE INDEX (index_users_on_category_id)
mysql-5.7
mysql-5.7
asked 2 mins ago
Alexandr ClimovAlexandr Climov
1
New contributor
Alexandr Climov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 2 mins ago
Alexandr ClimovAlexandr Climov
1
New contributor
Alexandr Climov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 2 mins ago
Alexandr ClimovAlexandr Climov
1
New contributor
Alexandr Climov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 2 mins ago
Alexandr ClimovAlexandr Climov
1
asked 2 mins ago
Alexandr ClimovAlexandr Climov
1
1
New contributor
Alexandr Climov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Alexandr Climov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Alexandr Climov 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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