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TODAY I LEARNED

How to add timeouts to slow queries

Sometimes some of your queries are taking too long to execute; you can specify optimizer hints and define timeouts for those queries.

Employee.optimizer_hints("MAX_EXECUTION_TIME(5000)").all

It will raise a StatementTimeout exception if the query takes longer than usual to execute

Example (for PostgreSQL with pg_hint_plan):

Employee.optimizer_hints("SeqScan(employees)", "Parallel(employees 8)")

Example (for MySQL):

Employee.optimizer_hints("MAX_EXECUTION_TIME(50000)", "NO_INDEX_MERGE(employees)")

There are many causes for sudden slow queries in many databases, such as missing index, wrong catching, and performance.

But this is a topic for another day!

Learned by Victor Velazquez on Feb 11, 2021

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