Question

recently inserted a lot of rows into these tables and now the query times out:

SELECT * FROM eng
WHERE english IN (SELECT eng FROM `eng-jap`)
ORDER BY lastmodified DESC

table eng-jap has about 25,000 rows, here is some stats on it:

Format          dynamic
Collation       utf8_general_ci
Rows            24,960
Row length ø    316
Row size ø      328 B
Next Autoindex  26,468
Type    Usage
Data    7,724.0 KiB
Index   264.0 KiB
Total   7,988.0 KiB

and for table eng:

Format          dynamic
Collation       utf8_general_ci
Rows            23,691
Row length ø    105
Row size ø      117 B
Next Autoindex  24,771
Type    Usage
Data    2,451.4 KiB
Index   260.0 KiB
Total   2,711.4 KiB

just select * from table gets (Query took 0.0002 sec) for either table

i just cant believe a very simple subquery like this with a couple k’s in each table needs more than the 160 sec timeout i have set, and then times out…

i hope its like a setting in my tables thats causing it. or mysql really cant do a query like this?

Answer 1

It’s having to cross-reference all the elements from one table with all the elements of the other.

Perhaps this might work better:

SELECT `eng`.* FROM `eng`
JOIN `eng-jap` ON `eng`.`english` = `eng-jap`.`eng`
ORDER BY `eng`.`lastmodified` DESC

Also make sure you have suitable Indexes defined. This will help speed up the query.