What does the slow query log in SQL mean?
The slow query log consists of SQL statements that take more than long_query_time seconds to execute and require at least min_examined_row_limit rows to be examined. The slow query log can be used to find queries that take a long time to execute and are therefore candidates for optimization.
How to write slow admin statements in MySQL?
If a log file already is open, it is closed and the new file is opened. The server writes less information to the slow query log if you use the –log-short-format option. To include slow administrative statements in the slow query log, enable the log_slow_admin_statements system variable.
What does it mean when mysql query takes 10 seconds?
By default, the value of system variable ‘long_query_time’ is 10. It means that any query which takes more than 10 seconds to execute will be considered as slow. Lets change the benchmark to 20 seconds as shown below: By default, queries that do not use indexes are not logged.
What is the time zone variable in MySQL?
The log_timestamps system variable controls the time zone of timestamps in messages written to the slow query log file (as well as to the general query log file and the error log).
What are the administrative statements in slow query?
Administrative statements include ALTER TABLE , ANALYZE TABLE , CHECK TABLE , CREATE INDEX , DROP INDEX , OPTIMIZE TABLE, and REPAIR TABLE . To include queries that do not use indexes for row lookups in the statements written to the slow query log, enable the log_queries_not_using_indexes system variable.
Can a 10 second query cause performance degradation?
The slow queries definition might differ in different cases since there are certain occasions that even a 10 second query is acceptable and still not slow. However, if your application is an OLTP, it’s very common that a 10 second or even a 5 second query is an issue or causes performance degradation to your database.