Why all queries are going into slow query log in MySQL

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Why all queries are going into slow query log in MySQL

We got a problem that every query that we ran in MySQL database got logged into slow query log even if the “Query_time” of that query is of sub seconds say 0.0034 whereas our “long_query_time” is set to 8 seconds. 

-- Reason we found out for this behavior:

After investigation we found out that the parameter “log_queries_not_using_indexes” was set to ON and that is why all queries land into slow query log as they were not using indexes. We turn it off and it solves our problem.

But if you do need logging of queries not using indexes then please do turn it on. 

set global log_queries_not_using_indexes=0;
set global log_queries_not_using_indexes=1;

or

set global log_queries_not_using_indexes=OFF;
set global log_queries_not_using_indexes=ON;

Remember it will not persist database restart, for that you have to do parameter setting in my.cnf

Some of the Parameters related to slow query log.

mysql> show global variables like '%slow%';
+---------------------+------------------------------+
| Variable_name       | Value                        |
+---------------------+------------------------------+
| slow_launch_time    | 2                            |
| slow_query_log      | ON                           |
| slow_query_log_file | /logmysql/log/mysql-slow.log |
+---------------------+------------------------------+

mysql> show global variables like '%indexes%';
+----------------------------------------+-------+
| Variable_name                          | Value |
+----------------------------------------+-------+
| log_queries_not_using_indexes          | OFF   |
| log_throttle_queries_not_using_indexes | 0     |
+----------------------------------------+-------+

mysql> show global variables like '%log_output%';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log_output    | FILE  |
+---------------+-------+

mysql> show global variables like '%long%';
+--------------------------------------------------------+----------+
| Variable_name                                          | Value    |
+--------------------------------------------------------+----------+
| long_query_time                                        | 5.000000 |
+--------------------------------------------------------+----------+

How to enable slow query in MySQL 5.6

[mysqld]

# Slow Query Log

slow-query-log=ON
slow_query_log_file=/logmysql/log/mysql-slow.log
long-query-time=5
log-output=FILE

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