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MySQL 8.0.18 Maintenance Release is Generally Available
Posted by: Edwin Desouza
Date: October 14, 2019 01:06PM

Hash join (WL#2241) This work by Erik Froseth implements hash join as a way of executing inner equi-joins in MySQL. For example SELECT * FROM t1 JOIN t2 ON t1.col1 = t2.col1; can be executed as a hash join in 8.0.18. Hash join does not need any index to execute, and is in most cases more efficient than the current block-nested loop algorithm.

EXPLAIN ANALYZE (WL#4168) This work by Steinar H. Gunderson implements EXPLAIN ANALYZE. EXPLAIN ANALYZE will run the query and then produce EXPLAIN output with additional information about how the optimizer estimates matched the actual execution. EXPLAIN ANALYZE is built on top of the new iterator executor and implements timing iterators on top of the real iterators, giving precise information about each call. For each iterator, we present the estimated execution cost, estimated number of returned rows, the time to return first row, the time to return all rows (i.e. actual cost), the number of rows returned by this iterator, and the number of loops. The overall query execution is presented as a tree structure where the nodes are iterators.

Iterator UNION (WL#13000) This work by Steinar H. Gunderson implements UNION, UNION ALL, WITH RECURSIVE and unqualified SELECT COUNT(*) in the new iterator executor framework.

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MySQL 8.0.18 Maintenance Release is Generally Available
October 14, 2019 01:06PM

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