If the server PID file is configured to be created in a world-writable location, the server now issues a warning suggesting use of a more secure location. (Bug #26585560)

NDB Cluster: MySQL NDB Cluster encountered race conditions compiling lex_hash.h. (Bug #24931655, Bug #83477, Bug #27470071, Bug #89482)

InnoDB: A REPLACE operation on a temporary table raised an assertion. (Bug #27225649, Bug #27229072)

InnoDB: A tablespace import operation on a server with a default row format of REDUNDANT raised an assertion failure. (Bug #26960215)

InnoDB: Evaluation of a subquery in a resolving function raised an assertion. (Bug #26909960)

InnoDB: An online DDL operation that rebuilds the table raised an assertion when the last insert log record to be applied was split across two pages. (Bug #26696448, Bug #87532)

InnoDB: A RENAME TABLE operation that renamed the schema failed to rename full-text search common auxiliary tables that were left behind when the full-text search index was removed previously, resulting in a assertion failure when attempting to drop the old schema. (Bug #26334149)

Replication: A number of changes were made to the binary log decoding procedure to improve handling of invalid or corrupted binary log entries. (Bug #24365972)

An invalid input polygon for spatial functions could lead to undefined server behavior. Now the server returns NULL. (Bug #27230859, Bug #88801)

Adding a unique index to an InnoDB table on which multiple locks were held could raise an assertion. (Bug #27216817)

For some statements, the FILE privilege was not properly checked. (Bug #27160888)

ST_Touches() could fail due to a missing null pointer check. (Bug #27081349)

A multiple-insert statement on a table containing a FULLTEXT key and a FTS_DOC_ID column caused a server error. (Bug #27041445, Bug #88267)

References: This issue is a regression of: Bug #22679185.

An ALTER TABLE operation attempted to set the AUTO_INCREMENT value for table in a discarded tablespace. (Bug #26935001)

Dropping an index from a system table could cause a server exit. (Bug #26881798)

A server exit could result from simultaneous attempts by multiple threads to register and deregister metadata Performance Schema objects. (Bug #26502135)

The thread pool plugin logged too much information for failed connections. (Bug #26368725, Bug #86863)

For debug builds, using KILL to terminate a stored routine could raise an assertion. Thanks to Laurynas Biveinis for the patch. (Bug #26040870, Bug #86260)

MySQL client programs could exit unexpectedly if malformed client/server protocol packets were received. (Bug #25471090)

Incorrect handling by the CONNECTION_CONTROL plugin of an internal hash led to spurious messages in the error log and eventual server exit. (Bug #25052009)

Building MySQL using parallel compilation sometimes failed with an attempt to compile sql_yacc.yy before lex_token.h had been created. (Bug #21680733, Bug #27470071, Bug #89482)

On Windows, sql_yacc.cc and sql_yacc.h were generated twice during the build process. This can lead to compilation failure if parallel processes are permitted. (Bug #19060850, Bug #27470071, Bug #89482)

The audit_log plugin did not log placeholder values for prepared statements. (Bug #16617026)

NULLIF() with a TIMESTAMP argument could produce truncated output. (Bug #12616286, Bug #61378)

MAX() for DATE values smaller than year 100 produced incorrect results. (Bug #12546797, Bug #61100)

Compilation could fail due to a missing dependency on lex_token.h for sql_yacc.cc.o. (Bug #76235, Bug #20678411, Bug #27470071, Bug #89482)

A WHERE condition of the form column_value < ALL (select_expression) did not always evaluate as TRUE when the select_expression did not return any rows. (Bug #61799, Bug #12762381)

The optimizer incorrectly optimized away a subquery selecting a MIN() or MAX() expression even when the subquery was correlated with or depended on an outer reference. An example of such a query is shown here:

SELECT (
  SELECT MIN(42) FROM t2 WHERE t2.pk = t1.pk
  ) AS scalar_subqry
  FROM t1;

In this case, the optimizer reduced SELECT MIN(42) FROM T2 to a constant value (42), and the correlation predicate WHERE T2.pk = T1.pk was never checked during query execution. (If the predicate were executed, it would not have qualifed any rows from the subquery, and would have evaluated as NULL.) (Bug #53485, Bug #11761032)