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MySQL 5.6 Release Notes  /  Changes in MySQL 5.6.49 (2020-07-13, General Availability)

Changes in MySQL 5.6.49 (2020-07-13, General Availability)

Configuration Notes

  • tcmalloc is no longer a permitted value for the mysqld_safe --malloc-lib option. (Bug #31372027)

Security Notes

Bugs Fixed

  • Partitioning: A query against a partitioned table, which used an ORDER BY, returned unordered results under the following conditions:

    • The table had a composite index with a prefix on one of the columns.

    • The query's WHERE clause contained an equality condition on the prefixed column.

    • The column with the prefix was the leftmost column in the index.

    • The column used in the ORDER BY was the rightmost column in the index.

    • The index was used for handling the ORDER BY.

    Our thanks to Quanan Han for the suggestion. (Bug #84070, Bug #25207522)

  • Replication: When a replication source server shuts down and restarts, its MEMORY tables become empty. To replicate this effect to replicas, the first time that the source uses a given MEMORY table after startup, it notifies replicas that the table must be emptied by writing a DELETE statement for that table to the binary log. Previously, the generated DELETE statement was written to the binary log statement cache for the current session, which could result in it being logged together with other statements under the same GTID, or logged without BEGIN and COMMIT statements. Also, in some situations, the generated DELETE statement could consume the GTID intended for the transaction that triggered it. The generated DELETE statement is now logged with accompanying BEGIN and COMMIT statements, and the resulting transaction is flushed to the binary log immediately after it is written to the statement cache, so that it always receives its own GTID and is kept separate from other transactions. (Bug #30527929, Bug #25681518, Bug #77729)

  • mysql_store_result() could fail to detect invalid data packets. (Bug #29921423)

  • The server sometimes mistakenly removed a subquery with a GROUP BY when optimizing a query, even in some cases when this subquery was used by an outer select. This could occur when the subquery also used an aggregate function. (Bug #28240054)