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When do you use parallel query in MySQL?
In the following sections, you can find an explanation of when parallel query is applied to a query. You can also find how to make sure that parallel query is applied where it provides the most benefit. The parallel query optimization provides the most benefit for long-running queries that take minutes or hours to complete.
Where does parallel processing occur in Aurora MySQL?
The parallel processing happens in the storage layer, independent of the Aurora MySQL server that serves as the query coordinator. By default, without parallel query, the processing for an Aurora query involves transmitting raw data to a single node within the Aurora cluster (the head node ).
Can you run more than one parallel query in Aurora?
Each Aurora DB instance can run only a certain number of parallel query sessions at one time. If a query has multiple parts that use parallel query, such as subqueries, joins, or UNION operators, those phases run in sequence. The statement only counts as a single parallel query session at any one time.
How is the number of parallel queries counted?
If a query has multiple parts that use parallel query, such as subqueries, joins, or UNION operators, those phases run in sequence. The statement only counts as a single parallel query session at any one time. You can monitor the number of active sessions using the parallel query status variables.
What to do if you have a problem with MySQL upgrade?
If you have a problem with mysql_upgrade try run it in very verbose mode: mysql_upgrade also saves the MariaDB version number in a file named mysql_upgrade_info in the data directory. This is used to quickly check whether all tables have been checked for this release so that table-checking can be skipped.
How to increase the parallelism of a query?
Another way to increase the parallelism will be to use “sharding” approach, for example with Shard Query. I’ve decided to test out the parallel (asynchronous) query execution with a relatively large table: I’ve used the US Flights Ontime performance database, which was originally used by Vadim in the old post Analyzing air traffic performance.
Can a partitioned table be used for a parallel query?
Currently, partitioned tables aren’t supported for parallel query. You can use partitioned tables in parallel query clusters. Queries against those tables use the non-parallel query processing path. Aurora uses a cost-based algorithm to determine whether to use the parallel query mechanism for each SQL statement.