Slow query logging for debugging of mysql configuration issues

Problem

flex.bi server gets very slow response times from import or report queries. Sometimes this causes a report execution timeouts, sometimes error messages about not being able to lock records or other database related messages in queues log file.

Solution

Enabling logging of slow queries might help to trace the cause of the problem if it is database configuration problem. Enter these commands in you mysql configuration (usually /etc/my.cnf file):
```
long_query_time                = 10
slow_query_log                 = 1
slow_query_log_file            = /var/log/mysql/log-slow-queries.log
```
Create the file /var/log/messages.log-slow-queries.log and make sure it can be accessed by the system user running mysql - usually user mysql.
For example:
```
mkdir /var/log/mysql
touch /var/log/mysql/log-slow-queries.log
chown mysql:mysql /var/log/mysql/log-slow-queries.log
```
Then restart mysql service and monitor the file.
```
systemctl restart mysqld
```