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MariaDB 10.2 explain high rows execution time low
Posted by: james wang
Date: June 27, 2020 07:30AM

Good day, All.

nnodb_version | 5.7.24
version | 10.2.21-MariaDB-log

execution plan:
select_type table type key key_len rows Extra
SIMPLE task ref index3 243 6234162 Using index condition; Using where
SIMPLE sys_user_group eq_ref PRIMARY 96 1 Using where

task table has 12m rows and index3 Cardinality only 4949

Execution plan shows that 6m rows will be scanned. However, when I actually run the query, it took less than 1 second (even in the first run).

It would be great if you would shed some light on this. I know you are very busy and truly appreciate your help. Thanks a lot in advance.

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MariaDB 10.2 explain high rows execution time low
June 27, 2020 07:30AM

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