MySQL bugs fixed by Aurora MySQL database engine updates

Fixed an issue where cache line value can be calculated incorrectly, causing a failure during database restart on Graviton-based instances. (Community Bug Fix #35479763)

Fixed an issue where some instances of subqueries within stored routines were not always handled correctly. (Community Bug Fix #35377192)

Fixed an issue that can cause higher CPU usage due to background TLS certificate rotation (Community Bug Fix #34284186).

Fixed an issue where InnoDB allowed the addition of INSTANT columns to tables in the MySQL system schema in Aurora MySQL versions lower than 3.05, which could lead to the server unexpectedly closing (database instance restarting) after upgrading to Aurora MySQL version 3.05.0. (Community Bug Fix #35625510).

Fixed an issue where cache line value can be incorrectly calculated, causing a failure during database restart on a Graviton instance. (Community Bug Fix #35479763)

Fixed an issue where some instances of subqueries within stored routines were not always handled correctly. (Community Bug Fix #35377192)

Fixed an issue that can cause higher CPU usage due to background TLS certificate rotation. (Community Bug Fix #34284186)

Fixed an issue where InnoDB allowed the addition of INSTANT columns to tables in the MySQL system schema in Aurora MySQL versions lower than 3.05, which could lead to the server unexpectedly closing (database instance restarting) after upgrading to Aurora MySQL version 3.05.0. (Community Bug Fix #35625510)

Fixed an issue where records_in_range performed an excessive number of disk reads for INSERT operations, leading to a gradual decline in performance. (Community Bug Fix #34976138)

Fixed an issue in InnoDB when, if a MySQL table in a system schema had an INSTANT ADD column added between Aurora MySQL versions 3.01 through Aurora MySQL versions 3.04, and after Aurora MySQL was upgraded to version 3.05.0, DMLs on these tables would result in the server unexpectedly closing. (Community Bug Fix #35625510)

Fixed an issue which can cause higher CPU utilization due to background TLS certificate rotation (Community Bug Fix #34284186)

Fixed an issue where cache line value can be calculated incorrectly, causing a failure during database restart on Graviton-based instances. (Community Bug Fix #35479763)

Repeated running of a stored routine, having as a subquery a SELECT statement containing multiple AND, OR, or XOR conditions, led to excessive consumption and possibly eventual exhaustion of virtual memory. (Community Bug Fix #33852530)

Fixed an issue which can cause higher CPU utilization due to background TLS certificate rotation (Community Bug Fix #34284186)

Fixed an issue where a buffer block containing intrinsic temporary table page was relocated during page traversal, causing an assertion failure (Bug# 33715694)

InnoDB: Prevent online DDL operations from accessing out-of-bounds memory (Bug# 34750489, Bug# 108925)

Fixed an issue which can sometimes produce incorrect query results while processing complex SQL statements consisting of multiple nested Common Table Expressions (CTEs) (Bug# 34572040, Bug# 34634469, Bug# 33856374)

Fixed an issue which can cause higher CPU utilization due to background TLS certificate rotation (Community Bug Fix #34284186)

Fixed an issue which can sometimes produce incorrect query results while processing complex SQL statements consisting of multiple nested Common Table Expressions (CTEs) (Bug #34572040, Bug #34634469, Bug #33856374)

InnoDB: A race condition between threads attempting to deinitialize and initialize statistics for the same table raised an assertion failure (Bug #33135425)

InnoDB: Prevent online DDL operations from accessing out-of-bounds memory (Bug #34750489, Bug #108925)

Fixed an issue where a buffer block containing intrinsic temporary table page was relocated during page traversal, causing an assertion failure (Bug #33715694)

Fixed an issue where sorts of some column types, including JSON and TEXT, sometimes exhausted the sort buffer if its size was not at least 15 times that of the largest row in the sort. Now the sort buffer need only be 15 times as large as the largest sort key. (Bug #103325, Bug #105532, Bug #32738705, Bug #33501541)

Fixed an issue wherein InnoDB did not always handle some legal names for table partitions correctly. (Bug #32208630)

Fixed an issue which, in certain conditions, may return incorrect results due to an inaccurate calculation of the nullability property when executing a query with an OR condition. (Bug #34060289)

Fixed an issue which, in certain conditions, may return incorrect results when the following two conditions are met:

(Bug #34060289)

Fixed an issue where incorrect AUTO_INCREMENT values were generated when the maximum integer column value was exceeded. The error was due to the maximum column value not being considered. The previous valid AUTO_INCREMENT value should have been returned in this case, causing a duplicate key error. (Bug #87926, Bug #26906787)

Fixed an issue where it was not possible to revoke the DROP privilege on the Performance Schema. (Bug #33578113)

Fixed an issue where a stored procedure containing an IF statement using EXISTS, which acted on one or more tables that were deleted and recreated between executions, did not execute correctly for subsequent invocations following the first one. (Bug #32855634).

Fixed an issue where a query that references a view in a subquery and an outer query block can cause an unexpected restart (Bug#32324234)

Fixed an issue which, in certain conditions, may return incorrect results due to an inaccurate calculation of the nullability property when executing a query with an OR condition. (Bug #34060289)

Fixed an issue which, in certain conditions, may return incorrect results when the following two conditions are met:

Fixed an issue where it wasn't possible to revoke the DROP privilege on the Performance Schema. (Bug #33578113)

Fixed an issue where a stored procedure containing an IF statement using EXISTS, which acted on one or more tables that were deleted and recreated between executions, did not execute correctly for subsequent invocations following the first one. (MySQL Bug #32855634).

Incorrect AUTO_INCREMENT values were generated when the maximum integer column value was exceeded. The error was due to the maximum column value not being considered. The previous valid AUTO_INCREMENT value should have been returned in this case, causing a duplicate key error. (Bug #87926, Bug #26906787)

Fixed an issue which can lead to a failure while upgrading an Aurora MySQL version 1 (Compatible with MySQL 5.6) database cluster containing user-created table with certain table IDs. Assignment of these table IDs may result in conflicting data dictionary table IDs while upgrading from Aurora MySQL version 2 (Compatible with MySQL 5.7) to Aurora MySQL version 3 (Compatible with MySQL 8.0). (Bug #33919635)

Fixed an issue where temporary tables bound to triggers while running statements could cause an unexpected DB engine restart.

Fixed a defect that can cause the server to exit when single-table UPDATE and DELETE statements using indexed expressions are run as prepared statements. (Bug #29257254)

Fixed an issue which can cause existing and new remote connections to stall when run concurrently with the SHOW PROCESSLIST statement (Community Bug #34857411)

Replication: Some binary log events were not always handled correctly (Bug #34617506)

Fixed processing of single character tokens by a Full-Text Search (FTS) parser plugin (Bug #35432973)

Fixed an issue which can cause higher CPU utilization due to background TLS certificate rotation. (Community Bug Fix #34284186)

Replication: Some binary log events were not always handled correctly. (Bug #34617506)

Fixed an issue which can cause higher CPU utilization due to background TLS certificate rotation. (Community Bug Fix #34284186)

In prepared statements, some types of subqueries could cause a server exit. (Bug #33100586)

Fixed an issue where the code for reading character set information from Performance Schema statement events tables (for example, events_statements_current) did not prevent simultaneous writing to that character set information. As a result, the SQL query text character set could be invalid, which could result in a server exit. With this fix, an invalid character set causes SQL_TEXT column truncation and prevents server exits. (Bug #23540008)

InnoDB: Backport of fix for Community Bug #25189192, Bug #84038. Fixed an issue where after a RENAME TABLE operation that moved a table to a different schema, InnoDB failed to update INNODB_SYS_DATAFILES data dictionary table. This resulted in an error on restart indicating that it could not locate the tablespace data file.

InnoDB: Fixed an issue where the server dropped an internally defined foreign key index when adding a new index and attempted to use a secondary index defined on a virtual generated column as the foreign key index, causing a server exit. InnoDB now permits a foreign key constraint to reference a secondary index defined on a virtual generated column. (Bug #23533396)

Fixed an issue where two sessions concurrently executing an INSERT ... ON DUPLICATE KEY UPDATE operation generated a deadlock. During partial rollback of a tuple, another session could update it. The fix for this bug reverts the fixes for Bug #11758237, Bug #17604730, and Bug #20040791. (Bug #25966845)

Fixed an issue where the EXECUTE and ALTER ROUTINE privileges weren't correctly granted to routine creators even with automatic_sp_privileges enabled. (Bug #27407480)

Backport of fix for Community Bug#24671968: Fixed an issue where a query could produce incorrect results if the WHERE clause contained a dependent subquery, the table had a secondary index on the columns in the select list followed by the columns in the subquery, and GROUP BY or DISTINCT permitted the query to use a Loose Index Scan.

Fixed an issue where replication breaks if a multi-table delete statement is issued against multiple tables with foreign keys. (Bug #80821)

Fixed an issue where in special cases certain slave errors are not ignored even with slave_skip_errors enabled. In cases when opening and locking a table failed or when field conversions failed on a server running row-based replication, the error is considered critical and the state of slave_skip_errors is ignored. The fix ensures that with slave_skip_errors) enabled, all errors reported during applying a transaction are correctly handled. (Bug #70640, Bug #17653275)

Fixed an issue where a SET PASSWORD statement was replicated from a MySQL 5.6 master to a MySQL 5.7 slave, or from a MySQL 5.7 master with the log_builtin_as_identified_by_password system variable set to ON to a MySQL 5.7 slave, the password hash was itself also hashed before being stored on the slave. The issue has now been fixed and the replicated password hash is stored as originally passed to the slave. (Bug#24687073)

Fixed an issue where serialization of a JSON value consisting of a large sub-document wrapped in many levels of JSON arrays, objects, or both, sometimes required an excessive amount time to complete. (Bug #23031146)

Statements that cannot be parsed (due, for example, to syntax errors) are no longer written to the slow query log. (Bug #33732907)

Fixed an issue where the code for reading character set information from Performance Schema statement events tables (for example, events_statements_current) did not prevent simultaneous writing to that character set information. As a result, the SQL query text character set could be invalid, which could result in a server exit. With this fix, an invalid character set causes SQL_TEXT column truncation and prevents server exits. (Bug #23540008)

Fixed an issue when an UPDATE required a temporary table having a primary key larger than 1024 bytes and that table was created using InnoDB, the server could exit. (Bug #25153670

Fixed an issue in InnoDB where an error in code related to table statistics raised an assertion in the dict0stats.cc (http://dict0stats.cc/) source file. (Bug #24585978)

A secondary index over a virtual column became corrupted when the index was built online. For UPDATE (https://dev.mysql.com/doc/refman/5.7/en/update.html) statements, we fix this as follows: If the virtual column value of the index record is set to NULL, then we generate this value from the cluster index record. (Bug #30556595)

ASSERTION "!OTHER_LOCK" IN LOCK_REC_ADD_TO_QUEUE (Bug #29195848)

HANDLE_FATAL_SIGNAL (SIG=11) IN __STRCHR_SSE2 (Bug #28653104)

Fixed an issue which a query interruption during a lock wait can cause an error in InnoDB. (Bug #28068293)

Interleaved transactions could sometimes deadlock the replica applier when the transaction isolation level was set to REPEATABLE READ. (Bug #25040331)

Fixed an issue which can cause binlog replicas to stall due to lock wait timeout.(Bug #27189701)

Interleaved transactions could sometimes deadlock the replica applier when the transaction isolation level was set to REPEATABLE READ. (Bug #25040331)

When a stored procedure contained a statement referring to a view which in turn referred to another view, the procedure could not be invoked successfully more than once. (Bug #87858, Bug #26864199)

For queries with many OR conditions, the optimizer now is more memory-efficient and less likely to exceed the memory limit imposed by the range_optimizer_max_mem_size system variable. In addition, the default value for that variable has been raised from 1,536,000 to 8,388,608. (Bug #79450, Bug #22283790)

Replication: In the next_event() function, which is called by a replica's SQL thread to read the next event from the relay log, the SQL thread did not release the relaylog.log_lock it acquired when it ran into an error (for example, due to a closed relay log), causing all other threads waiting to acquire a lock on the relay log to hang. With this fix, the lock is released before the SQL thread leaves the function under the situation. (Bug #21697821)

Fixing a memory corruption for ALTER TABLE with virtual column. (Bug #24961167; Bug #24960450)

Replication: Multithreaded replicas could not be configured with small queue sizes using slave_pending_jobs_size_max if they ever needed to process transactions larger than that size. Any packet larger than slave_pending_jobs_size_max was rejected with the error ER_MTS_EVENT_BIGGER_PENDING_JOBS_SIZE_MAX, even if the packet was smaller than the limit set by slave_max_allowed_packet. With this fix, slave_pending_jobs_size_max becomes a soft limit rather than a hard limit. If the size of a packet exceeds slave_pending_jobs_size_max but is less than slave_max_allowed_packet, the transaction is held until all the replica workers have empty queues, and then processed. All subsequent transactions are held until the large transaction has been completed. The queue size for replica workers can therefore be limited while still allowing occasional larger transactions. (Bug #21280753, Bug #77406)

Replication: When using a multithreaded replica, applier errors displayed worker ID data that was inconsistent with data externalized in Performance Schema replication tables. (Bug #25231367)

Replication: On a GTID-based replication replica running with -gtid-mode=ON, -log-bin=OFF, and using -slave-skip-errors, when an error was encountered that should be ignored Exec_Master_Log_Pos was not being correctly updated, causing Exec_Master_Log_Pos to loose synchrony with Read_master_log_pos. If a GTID_NEXT was not specified, the replica would never update its GTID state when rolling back from a single statement transaction. The Exec_Master_Log_Pos would not be updated because even though the transaction was finished, its GTID state would show otherwise. The fix removes the restraint of updating the GTID state when a transaction is rolled back only if GTID_NEXT is specified. (Bug #22268777)

Replication: A partially failed statement was not correctly consuming an auto-generated or specified GTID when binary logging was disabled. The fix ensures that a partially failed DROP TABLE, a partially failed DROP USER, or a partially failed DROP VIEW consume respectively the relevant GTID and save it into @@GLOBAL.GTID_EXECUTED and mysql.gtid_executed table when binary logging is disabled. (Bug #21686749)

Replication: Replicas running MySQL 5.7 could not connect to a MySQL 5.5 source due to an error retrieving the server_uuid, which is not part of MySQL 5.5. This was caused by changes in the method of retrieving the server_uuid. (Bug #22748612)

Binlog replication: GTID transaction skipping mechanism was not working properly for XA transaction before this fix. Server has a mechanism to skip (silently) a GTID transaction if it is already executed that particular transaction in the past. (BUG#25041920)

XA ROLLBACK statements that failed because an incorrect transaction ID was given, could be recorded in the binary log with the correct transaction ID, and could therefore be actioned by replication replicas. A check is now made for the error situation before binary logging takes place, and failed XA ROLLBACK statements are not logged. (Bug #26618925)

Replication: If a replica was set up using a CHANGE MASTER TO statement that did not specify the source log file name and source log position, then shut down before START SLAVE was issued, then restarted with the option -relay-log-recovery set, replication did not start. This happened because the receiver thread had not been started before relay log recovery was attempted, so no log rotation event was available in the relay log to provide the source log file name and source log position. In this situation, the replica now skips relay log recovery and logs a warning, then proceeds to start replication. (Bug #28996606, Bug #93397)

Replication: In row-based replication, a message that incorrectly displayed field lengths was returned when replicating from a table with a utf8mb3 column to a table of the same definition where the column was defined with a utf8mb4 character set. (Bug #25135304, Bug #83918)

Replication: When a RESET SLAVE statement was issued on a replication replica with GTIDs in use, the existing relay log files were purged, but the replacement new relay log file was generated before the set of received GTIDs for the channel had been cleared. The former GTID set was therefore written to the new relay log file as the PREVIOUS_GTIDS event, causing a fatal error in replication stating that the replica had more GTIDs than the source, even though the gtid_executed set for both servers was empty. Now, when RESET SLAVE is issued, the set of received GTIDs is cleared before the new relay log file is generated, so that this situation does not occur. (Bug #27411175)

Replication: With GTIDs in use for replication, transactions including statements that caused a parsing error (ER_PARSE_ERROR) could not be skipped manually by the recommended method of injecting an empty or replacement transaction with the same GTID. This action should result in the replica identifying the GTID as already used, and therefore skipping the unwanted transaction that shared its GTID. However, in the case of a parsing error, because the statement was parsed before the GTID was checked to see if it needed to be skipped, the replication applier thread stopped due to the parsing error, even though the intention was for the transaction to be skipped anyway. With this fix, the replication applier thread now ignores parsing errors if the transaction concerned needs to be skipped because the GTID was already used. Note that this behavior change does not apply in the case of workloads consisting of binary log output produced by mysqlbinlog. In that situation, there would be a risk that a transaction with a parsing error that immediately follows a skipped transaction would also be silently skipped, when it ought to raise an error. (Bug #27638268)

Replication: Enable the SQL thread to GTID skip a partial transaction. (Bug #25800025)

Replication: When a negative or fractional timeout parameter was supplied to WAIT_UNTIL_SQL_THREAD_AFTER_GTIDS(), the server behaved in unexpected ways. With this fix:

Replication: If the WAIT_FOR_EXECUTED_GTID_SET() function was used with a timeout value including a fractional part (for example, 1.5), an error in the casting logic meant that the timeout was rounded down to the nearest whole second, and to zero for values less than 1 second (for example, 0.1). The casting logic has now been corrected so that the timeout value is applied as originally specified with no rounding. Thanks to Dirkjan Bussink for the contribution. (Bug #29324564, Bug #94247)

With GTIDs enabled, XA COMMIT on a disconnected XA transaction within a multiple-statement transaction raised an assertion. (Bug #22173903)

Replication: An assertion was raised in debug builds if an XA ROLLBACK statement was issued for an unknown transaction identifier when the gtid_next value had been set manually. The server now does not attempt to update the GTID state if an XA ROLLBACK statement fails with an error. (Bug #27928837, Bug #90640)

Fix wrong sorting order issue when multiple CASE functions are used in ORDER BY clause. (Bug#22810883)

Some queries that used ordering could access an uninitialized column during optimization and cause a server exit. (Bug #27389294)

ASSERTION !M_PREBUILT->TRX->CHECK_FOREIGNS. (Bug #23533396)

Replication:* A locking issue in the WAIT_FOR_EXECUTED_GTID_SET() function could cause the server to hang in certain circumstances. The issue has now been corrected. (Bug #29550513)

Replication: Interleaved transactions could sometimes deadlock the slave applier when the transaction isolation level was set to REPEATABLE READ. (Bug #25040331)

For a table having a TIMESTAMP or DATETIME column having a default of CURRENT_TIMESTAMP, the column could be initialized to 0000-00-00 00:00:00 if the table had a BEFORE INSERT trigger. (Bug #25209512, Bug #84077)

For an INSERT statement for which the VALUES list produced values for the second or later row using a subquery containing a join, the server could exit after failing to resolve the required privileges. (Bug #23762382)

Bug #23762382 - INSERT VALUES QUERY WITH JOIN IN A SELECT CAUSES INCORRECT BEHAVIOR.

Bug #25209512 - CURRENT_TIMESTAMP PRODUCES ZEROS IN TRIGGER.

Bug #25289359: A full-text cache lock taken when data is synchronized was not released if the full-text cache size exceeded the full-text cache size limit.

Bug #29138644: Manually changing the system time while the MySQL server was running caused page cleaner thread delays.

Bug #25222337: A NULL virtual column field name in a virtual index caused a server exit during a field name comparison that occurs while populating virtual columns affected by a foreign key constraint.

Bug #25053286: Executing a stored procedure containing a query that accessed a view could allocate memory that was not freed until the session ended.

Bug #25586773: Executing a stored procedure containing a statement that created a table from the contents of certain SELECT statements could result in a memory leak.

Bug #28834208: During log application, after an OPTIMIZE TABLE operation, InnoDB did not populate virtual columns before checking for virtual column index updates.

Bug #26666274: Infinite loop in performance schema buffer container due to 32-bit unsigned integer overflow.

INSERTING 64K SIZE RECORDS TAKE TOO MUCH TIME. (Bug#23031146)

Fixed an issue in the Full-text ngram parser when dealing with tokens containing ' ' (space), '%', or ','. Customers should rebuild their FTS indexes if using ngram parser. (Bug #25873310)

Fixed an issue that could cause engine restart during query execution with nested SQL views. (Bug #27214153, Bug #26864199)

InnoDB: Concurrent XA transactions that ran successfully to the XA prepare stage on the master conflicted when replayed on the slave, resulting in a lock wait timeout in the applier thread. The conflict was due to the GAP lock range which differed when the transactions were replayed serially on the slave. To prevent this type of conflict, GAP locks taken by XA transactions in READ COMMITTED isolation level are now released (and no longer inherited) when XA transactions reach the prepare stage. (Bug #27189701, Bug #25866046)

InnoDB: A gap lock was taken unnecessarily during foreign key validation while using the READ COMMITTED isolation level. (Bug #25082593)

Replication: When using XA transactions, if a lock wait timeout or deadlock occurred for the applier (SQL) thread on a replication slave, the automatic retry did not work. The cause was that while the SQL thread would do a rollback, it would not roll the XA transaction back. This meant that when the transaction was retried, the first event was XA START which was invalid as the XA transaction was already in progress, leading to an XAER_RMFAIL error. (Bug #24764800)

Replication: Interleaved transactions could sometimes deadlock the slave applier when the transaction isolation level was set to REPEATABLE READ. (Bug #25040331)

Replication: The value returned by a SHOW SLAVE STATUS statement for the total combined size of all existing relay log files (Relay_Log_Space) could become much larger than the actual disk space used by the relay log files. The I/O thread did not lock the variable while it updated the value, so the SQL thread could automatically delete a relay log file and write a reduced value before the I/O thread finished updating the value. The I/O thread then wrote its original size calculation, ignoring the SQL thread's update and so adding back the space for the deleted file. The Relay_Log_Space value is now locked during updates to prevent concurrent updates and ensure an accurate calculation. (Bug #26997096, Bug #87832)

For an INSERT statement for which the VALUES list produced values for the second or later row using a subquery containing a join, the server could exit after failing to resolve the required privileges. (Bug #23762382)

For a table having a TIMESTAMP or DATETIME column having a default of CURRENT_TIMESTAMP, the column could be initialized to 0000-00-00 00:00:00 if the table had a BEFORE INSERT trigger. (Bug #25209512, Bug #84077)

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

Executing a stored procedure containing a statement that created a table from the contents of certain SELECT statements could result in a memory leak. (Bug #25586773)

Executing a stored procedure containing a query that accessed a view could allocate memory that was not freed until the session ended. (Bug #25053286)

Certain cases of subquery materialization could cause a server exit. These queries now produce an error suggesting that materialization be disabled. (Bug #26402045)

Queries with many left joins were slow if join buffering was used (for example, using the block nested loop algorithm). (Bug #18898433, Bug #72854)

The optimizer skipped the second column in a composite index when executing an inner join with a LIKE clause against the second column. (Bug #28086754)

Bug #23104498: Fixed an issue in Performance Schema in reporting total memory used. (https://github.com/mysql/mysql-server/commit/20b6840df5452f47313c6f9a6ca075bfbc00a96b)

Bug #22551677: Fixed an issue in Performance Schema that could lead to the database engine crashing when attempting to take it offline. (https://github.com/mysql/mysql-server/commit/05e2386eccd32b6b444b900c9f8a87a1d8d531e9)

Bug #23550835, Bug #23298025, Bug #81464: Fixed an issue in Performance Schema that causes a database engine crash due to exceeding the capacity of an internal buffer. (https://github.com/mysql/mysql-server/commit/b4287f93857bf2f99b18fd06f555bbe5b12debfc, https://github.com/mysql/mysql-server/commit/b4287f93857bf2f99b18fd06f555bbe5b12debfc)

Bug #26251621: INCORRECT BEHAVIOR WITH TRIGGER AND GCOL

Bug #22574695: ASSERTION `!TABLE || (!TABLE->READ_SET || BITMAP_IS_SET(TABLE->READ_SET, FIEL

Bug #25966845: INSERT ON DUPLICATE KEY GENERATE A DEADLOCK

Bug #23070734: CONCURRENT TRUNCATE TABLES CAUSE STALL

Bug #26191879: FOREIGN KEY CASCADES USE EXCESSIVE MEMORY

Bug #20989615: INNODB AUTO_INCREMENT PRODUCES SAME VALUE TWICE

Bug#23054591: PURGE BINARY LOGS TO is reading the whole binlog file and causing MySql to stall

Bug #23070734, Bug #80060: Concurrent TRUNCATE TABLEs cause stalls

Bug #23103937: PS_TRUNCATE_ALL_TABLES() DOES NOT WORK IN SUPER_READ_ONLY MODE

Bug#22551677: When taking the server offline, a race condition within the Performance Schema could lead to a server exit.

Bug #27082268: Invalid FTS sync synchronization.

BUG #12589870: Fixed an issues which causes a restart with multi-query statement when query cache is enabled.

Bug #26402045: Certain cases of subquery materialization could cause a server exit. These queries now produce an error suggesting that materialization be disabled.

Bug #18898433: Queries with many left joins were slow if join buffering was used (for example, using the block nested loop algorithm).

Bug #25222337: A NULL virtual column field name in a virtual index caused a server exit during a field name comparison that occurs while populating virtual columns affected by a foreign key constraint. (https://github.com/mysql/mysql-server/commit/273d5c9d7072c63b6c47dbef6963d7dc491d5131)

Bug #25053286: Executing a stored procedure containing a query that accessed a view could allocate memory that was not freed until the session ended. (https://github.com/mysql/mysql-server/commit/d7b37d4d141a95f577916448650c429f0d6e193d)

Bug #25586773: Executing a stored procedure containing a statement that created a table from the contents of certain SELECT (https://dev.mysql.com/doc/refman/5.7/en/select.html) statements could result in a memory leak. (https://github.com/mysql/mysql-server/commit/88301e5adab65f6750f66af284be410c4369d0c1)

Bug #26666274: INFINITE LOOP IN PERFORMANCE SCHEMA BUFFER CONTAINER.

Bug #23550835, Bug #23298025, Bug #81464: A SELECT Performance Schema tables when an internal buffer was full could cause a server exit.

Bug#23054591: PURGE BINARY LOGS TO is reading the whole binlog file and causing MySql to stall

REVERSE SCAN ON A PARTITIONED TABLE DOES ICP - ORDER BY DESC (Bug #24929748).

JSON_OBJECT CREATES INVALID JSON CODE (Bug#26867509).

INSERTING LARGE JSON DATA TAKES AN INORDINATE AMOUNT OF TIME (Bug #22843444).

PARTITIONED TABLES USE MORE MEMORY IN 5.7 THAN 5.6 (Bug #25080442).

BUG#13651665 INNODB MAY BE UNABLE TO LOAD TABLE DEFINITION AFTER RENAME

BUG#21371070 INNODB: CANNOT ALLOCATE 0 BYTES.

BUG#21378944 FTS ASSERT ENC.SRC_ILIST_PTR != NULL, FTS_OPTIMIZE_WORD(), OPTIMIZE TABLE

BUG#21508537 ASSERTION FAILURE UT_A(!VICTIM_TRX->READ_ONLY)

BUG#21983865 UNEXPECTED DEADLOCK WITH INNODB_AUTOINC_LOCK_MODE=0

BUG#22679185 INVALID INNODB FTS DOC ID DURING INSERT

BUG#22899305 GCOLS: ASSERTION: !(COL->PRTYPE & 256).

BUG#22956469 MEMORY LEAK INTRODUCED IN 5.7.8 IN MEMORY/INNODB/OS0FILE

BUG#22996488 CRASH IN FTS_SYNC_INDEX WHEN DOING DDL IN A LOOP

BUG#23014521 GCOL:INNODB: ASSERTION: !IS_V

BUG#23021168 REPLICATION STOPS AFTER TRX IS ROLLED BACK ASYNC

BUG#23052231 ASSERTION: ADD_AUTOINC < DICT_TABLE_GET_N_USER_COLS

BUG#23149683 ROTATE INNODB MASTER KEY WITH KEYRING_OKV_CONF_DIR MISSING: SIGSEGV; SIGNAL 11

BUG#23762382 INSERT VALUES QUERY WITH JOIN IN A SELECT CAUSES INCORRECT BEHAVIOR

BUG#25209512 CURRENT_TIMESTAMP PRODUCES ZEROS IN TRIGGER

BUG#26626277 BUG IN "INSERT... ON DUPLICATE KEY UPDATE" QUERY

BUG#26734162 INCORRECT BEHAVIOR WITH INSERT OF BLOB + ON DUPLICATE KEY UPDATE

BUG#27460607 INCORRECT WHEN INSERT SELECT's SOURCE TABLE IS EMPTY

Replication: While a SHOW BINLOG EVENTS statement was executing, any parallel transaction was blocked. The fix ensures that the SHOW BINLOG EVENTS process now only acquires a lock for the duration of calculating the file's end position, therefore parallel transactions are not blocked for long durations. (Bug #76618, Bug #20928790)

Binlog events with ALTER TABLE ADD COLUMN ALGORITHM=QUICK will be rewritten as ALGORITHM=DEFAULT to be compatible with the community edition.

BUG #22350047: IF CLIENT KILLED AFTER ROLLBACK TO SAVEPOINT PREVIOUS STMTS COMMITTED

Bug #29915479: RUNNING COM_REGISTER_SLAVE WITHOUT COM_BINLOG_DUMP CAN RESULTS IN SERVER EXIT

Bug #30441969: BUG #29723340: MYSQL SERVER CRASH AFTER SQL QUERY WITH DATA ?AST

Bug #30628268: OUT OF MEMORY CRASH

Bug #27081349: UNEXPECTED BEHAVIOUR WHEN DELETE WITH SPATIAL FUNCTION

Bug #27230859: UNEXPECTED BEHAVIOUR WHILE HANDLING INVALID POLYGON"

Bug #27081349: UNEXPECTED BEHAVIOUR WHEN DELETE WITH SPATIAL"

Bug #26935001: ALTER TABLE AUTO_INCREMENT TRIES TO READ INDEX FROM DISCARDED TABLESPACE

Bug #29770705: SERVER CRASHED WHILE EXECUTING SELECT WITH SPECIFIC WHERE CLAUSE

Bug #27659490: SELECT USING DYNAMIC RANGE AND INDEX MERGE USE TOO MUCH MEMORY(OOM)

Bug #24786290: REPLICATION BREAKS AFTER BUG #74145 HAPPENS IN MASTER

Bug #27703912: EXCESSIVE MEMORY USAGE WITH MANY PREPARE

Bug #20527363: TRUNCATE TEMPORARY TABLE CRASH: !DICT_TF2_FLAG_IS_SET(TABLE, DICT_TF2_TEMPORARY)

Bug#23103937 PS_TRUNCATE_ALL_TABLES() DOES NOT WORK IN SUPER_READ_ONLY MODE

Bug #25053286: USE VIEW WITH CONDITION IN PROCEDURE CAUSES INCORRECT BEHAVIOR (fixed in 5.6.36)

Bug #25586773: INCORRECT BEHAVIOR FOR CREATE TABLE SELECT IN A LOOP IN SP (fixed in 5.6.39)

Bug #27407480: AUTOMATIC_SP_PRIVILEGES REQUIRES NEED THE INSERT PRIVILEGES FOR MYSQL.USER TABLE

Bug #26997096: relay_log_space value is not updated in a synchronized manner so that its value is sometimes much higher than the actual disk space used by relay logs.

Bug#15831300 SLAVE_TYPE_CONVERSIONS=ALL_NON_LOSSY NOT WORKING AS EXPECTED

SSL Bug backport Bug #17087862, Bug #20551271

Bug #16894092: PERFORMANCE REGRESSION IN 5.6.6+ FOR INSERT INTO ... SELECT ... FROM (fixed in 5.6.15).

Port a bug fix related to SLAVE_TYPE_CONVERSIONS.

Bug #26654685: A corrupt index ID encountered during a foreign key check raised an assertion

Bug #15831300: By default, when promoting integers from a smaller type on the master to a larger type on the slave (for example, from a SMALLINT column on the master to a BIGINT column on the slave), the promoted values are treated as though they are signed. Now in such cases it is possible to modify or override this behavior using one or both of ALL_SIGNED, ALL_UNSIGNED in the set of values specified for the slave_type_conversions server system variable. For more information, see Row-based replication: attribute promotion and demotion, as well as the description of the variable.

Bug #17449901: With foreign_key_checks=0, InnoDB permitted an index required by a foreign key constraint to be dropped, placing the table into an inconsistent and causing the foreign key check that occurs at table load to fail. InnoDB now prevents dropping an index required by a foreign key constraint, even with foreign_key_checks=0. The foreign key constraint must be removed before dropping the foreign key index.

BUG #20768847: An ALTER TABLE ... DROP INDEX operation on a table with foreign key dependencies raised an assertion.

Bug#16346241 - SERVER CRASH IN ITEM_PARAM::QUERY_VAL_STR

Bug#17733850 - NAME_CONST() CRASH IN ITEM_NAME_CONST::ITEM_NAME_CONST()

Bug #20989615 - INNODB AUTO_INCREMENT PRODUCES SAME VALUE TWICE

Bug #20181776 - ACCESS CONTROL DOESN'T MATCH MOST SPECIFIC HOST WHEN IT CONTAINS WILDCARD

Bug #27326796 - MYSQL CRASH WITH INNODB ASSERTION FAILURE IN FILE PARS0PARS.CC

Bug #20590013 - IF YOU HAVE A FULLTEXT INDEX AND DROP IT YOU CAN NO LONGER PERFORM ONLINE DDL

Bug #19929406: HANDLE_FATAL_SIGNAL (SIG=11) IN __MEMMOVE_SSSE3_BACK FROM STRING::COPY

Bug #17059925: For UNION statements, the rows-examined value was calculated incorrectly. This was manifested as too-large values for the ROWS_EXAMINED column of Performance Schema statement tables (such as events_statements_current).

Bug #11827369: Some queries with SELECT ... FROM DUAL nested subqueries raised an assertion.

Bug #16311231: Incorrect results were returned if a query contained a subquery in an IN clause that contained an XOR operation in the WHERE clause.

Bug #19929406: HANDLE_FATAL_SIGNAL (SIG=11) IN __MEMMOVE_SSSE3_BACK FROM STRING::COPY

Bug #17059925: For UNION statements, the rows-examined value was calculated incorrectly. This was manifested as too-large values for the ROWS_EXAMINED column of Performance Schema statement tables (such as events_statements_current).

Bug #11827369: Some queries with SELECT ... FROM DUAL nested subqueries raised an assertion.

Bug #16311231: Incorrect results were returned if a query contained a subquery in an IN clause that contained an XOR operation in the WHERE clause.

CVE-2018-2696

CVE-2015-4737

Bug #19929406: HANDLE_FATAL_SIGNAL (SIG=11) IN __MEMMOVE_SSSE3_BACK FROM STRING::COPY

Bug #17059925: For UNION statements, the rows-examined value was calculated incorrectly. This was manifest as too-large values for the ROWS_EXAMINED column of Performance Schema statement tables (such as events_statements_current).

Bug #11827369: Some queries with SELECT ... FROM DUAL nested subqueries raised an assertion.

Bug #16311231: Incorrect results were returned if a query contained a subquery in an IN clause which contained an XOR operation in the WHERE clause.

BUG #32917: DETECT ORPHAN TEMP-POOL FILES, AND HANDLE GRACEFULLY

BUG #63144 CREATE TABLE IF NOT EXISTS METADATA LOCK IS TOO RESTRICTIVE

BUG #13418638: CREATE TABLE IF NOT EXISTS METADATA LOCK IS TOO RESTRICTIVE

Drop index on a foreign key column leads to missing table. (Bug #16208542)

Memory leak in add_derived_key(). (Bug #76349)

For partitioned tables, queries could return different results depending on whether Index Merge was used. (Bug #16862316)

Queries using the index_merge optimization (see Index merge optimization) could return invalid results when run against tables that were partitioned by HASH. (Bug #17588348)

For an ALTER TABLE statement that renamed or changed the default value of a BINARY column, the alteration was done using a table copy and not in place. (Bug #67141, Bug #14735373, Bug #69580, Bug #17024290)

An outer join between a regular table and a derived table that is implicitly groups could cause a server exit. (Bug #16177639)

LAST_INSERT_ID is replicated incorrectly if replication filters are used (Bug #69861)

Query returns different results depending on whether INDEX_MERGE setting (Bug #16862316)

Query proc re-execute of stored routine, inefficient query plan (Bug #16346367)

InnoDB FTS : Assert in FTS_CACHE_APPEND_DELETED_DOC_IDS (Bug #18079671)

Assert RBT_EMPTY(INDEX_CACHE->WORDS) in ALTER TABLE CHANGE COLUMN (Bug #17536995)

InnoDB fulltext search doesn't find records when savepoints are involved (Bug #70333, Bug #17458835)

Reverted — MySQL instance stalling "doing SYNC index" (Bug #73816)

Reverted — Assert RBT_EMPTY(INDEX_CACHE->WORDS) in ALTER TABLE CHANGE COLUMN (Bug #17536995)

Reverted — InnoDB Fulltext search doesn't find records when savepoints are involved (Bug #70333)

CREATE USER accepts plugin and password hash, but ignores the password hash (Bug #78033)

The partitioning engine adds fields to the read bit set to be able to return entries sorted from a partitioned index. This leads to the join buffer will try to read unneeded fields. Fixed by not adding all partitioning fields to the read_set,but instead only sort on the already set prefix fields in the read_set. Added a DBUG_ASSERT that if doing key_cmp, at least the first field must be read (Bug #16367691).

MySQL instance stalling "doing SYNC index" (Bug #73816)

Assert RBT_EMPTY(INDEX_CACHE->WORDS) in ALTER TABLE CHANGE COLUMN (Bug #17536995)

InnoDB Fulltext search doesn't find records when savepoints are involved (Bug #70333)

Ignorable events don't work and are not tested (Bug #74683)

NEW->OLD ASSERT FAILURE 'GTID_MODE > 0' (Bug #20436436)

Reloading a table that was evicted while empty caused an AUTO_INCREMENT value to be reset. (Bug #21454472, Bug #77743)

An index record was not found on rollback due to inconsistencies in the purge_node_t structure. The inconsistency resulted in warnings and error messages such as "error in sec index entry update", "unable to purge a record", and "tried to purge sec index entry not marked for deletion". (Bug #19138298, Bug #70214, Bug #21126772, Bug #21065746)

Wrong stack size calculation for qsort operation leads to stack overflow. (Bug #73979)

Record not found in an index upon rollback. (Bug #70214, Bug #72419)

ALTER TABLE add column TIMESTAMP on update CURRENT_TIMESTAMP inserts ZERO-datas (Bug #17392)

Reloading a table that was evicted while empty caused an AUTO_INCREMENT value to be reset. (Bug #21454472, Bug #77743)

An index record was not found on rollback due to inconsistencies in the purge_node_t structure. The inconsistency resulted in warnings and error messages such as "error in sec index entry update", "unable to purge a record", and "tried to purge sec index entry not marked for deletion". (Bug #19138298, Bug #70214, Bug #21126772, Bug #21065746)

Wrong stack size calculation for qsort operation leads to stack overflow. (Bug #73979)

Record not found in an index upon rollback. (Bug #70214, Bug #72419)

ALTER TABLE add column TIMESTAMP on update CURRENT_TIMESTAMP inserts ZERO-datas (Bug #17392)

Running ALTER table DROP foreign key simultaneously with another DROP operation causes the table to disappear. (Bug #16095573)

Some INFORMATION_SCHEMA queries that used ORDER BY did not use a filesort optimization as they did previously. (Bug #16423536)

FOUND_ROWS () returns the wrong count of rows on a table. (Bug #68458)

The server fails instead of giving an error when too many temp tables are open. (Bug #18948649)

UNION of derived tables returns wrong results with '1=0/false'-clauses. (Bug #69471)

Server crashes in ITEM_FUNC_GROUP_CONCAT::FIX_FIELDS on 2nd execution of stored procedure. (Bug #20755389)

Avoid MySQL queries from stalling for too long during FTS cache sync to disk by offloading the cache sync task to a separate thread, as soon as the cache size crosses 10% of the total size. (Bugs #22516559, #73816)

OpenSSL changed the Diffie-Hellman key length parameters due to the LogJam issue. (Bug #18367167)

When dropping all indexes on a column with multiple indexes, InnoDB failed to block a DROP INDEX operation when a foreign key constraint requires an index. (Bug #16896810)

Solve add foreign key constraint crash. (Bug #16413976)

Fixed a crash when fetching a cursor in a stored procedure, and analyzing or flushing the table at the same time. (Bug # 18158639)

Fixed an auto-increment bug when a user alters a table to change the AUTO_INCREMENT value to less than the maximum auto-increment column value. (Bug # 16310273)

Improve scalability by partitioning LOCK_grant lock. (Port WL #8355)

Opening cursor on SELECT in stored procedure causes segfault. (Port Bug #16499751)

MySQL gives the wrong result with some special usage. (Bug #11751794)

Crash in GET_SEL_ARG_FOR_KEYPART – caused by patch for bug #11751794. (Bug #16208709)

Wrong results for a simple query with GROUP BY. (Bug #17909656)

Extra rows on semijoin query with range predicates. (Bug #16221623)

Adding an ORDER BY clause following an IN subquery could cause duplicate rows to be returned. (Bug #16308085)

Crash with explain for a query with loose scan for GROUP BY, MyISAM. (Bug #16222245)

Loose index scan with quoted int predicate returns random data. (Bug #16394084)

If the optimizer was using a loose index scan, the server could exit while attempting to create a temporary table. (Bug #16436567)

COUNT(DISTINCT) should not count NULL values, but they were counted when the optimizer used loose index scan. (Bug #17222452)

If a query had both MIN()/MAX() and aggregate_function(DISTINCT) (for example, SUM(DISTINCT)) and was executed using loose index scan, the result values of MIN()/MAX() were set improperly. (Bug #17217128)

SLAVE CAN'T CONTINUE REPLICATION AFTER MASTER'S CRASH RECOVERY (Port Bug #17632285)

BACKPORT Bug #18694052 FIX FOR ASSERTION `!M_ORDERED_REC_BUFFER' FAILED TO 5.6 (Port Bug #18305270)

SEGV IN MEMCPY(), HA_PARTITION::POSITION (Port Bug # 18383840)

WRONG RESULTS WITH PARTITIONING,INDEX_MERGE AND NO PK (Port Bug # 18167648)

FLUSH TABLES FOR EXPORT: ASSERTION IN HA_PARTITION::EXTRA (Port Bug # 16943907)

SERVER CRASH IN VIRTUAL HA_ROWS HANDLER::MULTI_RANGE_READ_INFO_CONST (Port Bug # 16164031)

RANGE OPTIMIZER CRASHES IN SEL_ARG::RB_INSERT() (Port Bug # 16241773)

Addressed incomplete fix in MySQL full text search affecting tables where the database name begins with a digit. (Port Bug #17607956)

SEGV in FTSPARSE(). (Bug #16446108)

InnoDB data dictionary is not updated while renaming the column. (Bug #19465984)

FTS crash after renaming table to different database. (Bug #16834860)

Failed preparing of trigger on truncated tables cause error 1054. (Bug #18596756)

Metadata changes might cause problems with trigger execution. (Bug #18684393)

Materialization is not chosen for long UTF8 VARCHAR field. (Bug #17566396)

Poor execution plan when ORDER BY with limit X. (Bug #16697792)

Backport bug #11765744 TO 5.1, 5.5 AND 5.6. (Bug #17083851)

Mutex issue in SQL/SQL_SHOW.CC resulting in SIG6. Source likely FILL_VARIABLES. (Bug #20788853)

Backport bug #18008907 to 5.5+ versions. (Bug #18903155)

Adapt fix for a stack overflow error in MySQL 5.7. (Bug #19678930)

Killing a query inside innodb causes it to eventually crash with an assertion. (Bug #1608883)

For failure to create a new thread for the event scheduler, event execution, or new connection, no message was written to the error log. (Bug #16865959)

If one connection changed its default database and simultaneously another connection executed SHOW PROCESSLIST, the second connection could access invalid memory when attempting to display the first connection's default database memory. (Bug #11765252)

PURGE BINARY LOGS by design does not remove binary log files that are in use or active, but did not provide any notice when this occurred. (Bug #13727933)

For some statements, memory leaks could result when the optimizer removed unneeded subquery clauses. (Bug #15875919)

During shutdown, the server could attempt to lock an uninitialized mutex. (Bug #16016493)

A prepared statement that used GROUP_CONCAT() and an ORDER BY clause that named multiple columns could cause the server to exit. ( Bug #16075310)

Performance Schema instrumentation was missing for replica worker threads. (Bug #16083949)

STOP SLAVE could cause a deadlock when issued concurrently with a statement such as SHOW STATUS that retrieved the values for one or more of the status variables Slave_retried_transactions, Slave_heartbeat_period, Slave_received_heartbeats, Slave_last_heartbeat, or Slave_running. (Bug #16088188)

A full-text query using Boolean mode could return zero results in some cases where the search term was a quoted phrase. (Bug #16206253)

The optimizer's attempt to remove redundant subquery clauses raised an assertion when executing a prepared statement with a subquery in the ON clause of a join in a subquery. (Bug #16318585)

GROUP_CONCAT unstable, crash in ITEM_SUM::CLEAN_UP_AFTER_REMOVAL. (Bug #16347450)

Attempting to replace the default InnoDB full-text search (FTS) stopword list by creating an InnoDB table with the same structure as INFORMATION_SCHEMA.INNODB_FT_DEFAULT_STOPWORD would result in an error. (Bug #16373868)

After the client thread on a worker performed a FLUSH TABLES WITH READ LOCK and was followed by some updates on the master, the worker hung when executing SHOW SLAVE STATUS. (Bug #16387720)

When parsing a delimited search string such as "abc-def" in a full-text search, InnoDB now uses the same word delimiters as MyISAM. (Bug #16419661)

Crash in FTS_AST_TERM_SET_WILDCARD. (Bug #16429306)

SEGFAULT in FTS_AST_VISIT() for FTS RQG test. (Bug # 16435855)

For debug builds, when the optimizer removed an Item_ref pointing to a subquery, it caused a server exit. (Bug #16509874)

Full-text search on InnoDB tables failed on searches for literal phrases combined with + or - operators. (Bug #16516193)

START SLAVE failed when the server was started with the options--master-info-repository=TABLE relay-log-info-repository=TABLE and with autocommit set to 0, together with --skip-slave-start. (Bug #16533802)

Very large InnoDB full-text search (FTS) results could consume an excessive amount of memory. (Bug #16625973)

In debug builds, an assertion could occur in OPT_CHECK_ORDER_BY when using binary directly in a search string, as binary might include NULL bytes and other non-meaningful characters. (Bug #16766016)

For some statements, memory leaks could result when the optimizer removed unneeded subquery clauses. (Bug #16807641)

It was possible to cause a deadlock after issuing FLUSH TABLES WITH READ LOCK by issuing STOP SLAVE in a new connection to the worker, then issuing SHOW SLAVE STATUS using the original connection. (Bug #16856735)

GROUP_CONCAT() with an invalid separator could cause a server exit. (Bug #16870783)

The server did excessive locking on the LOCK_active_mi and active_mi->rli->data_lock mutexes for any SHOW STATUS LIKE 'pattern' statement, even when the pattern did not match status variables that use those mutexes (Slave_heartbeat_period, Slave_last_heartbeat, Slave_received_heartbeats, Slave_retried_transactions, Slave_running). (Bug #16904035)

A full-text search using the IN BOOLEAN MODE modifier would result in an assertion failure. (Bug #16927092)

Full-text search on InnoDB tables failed on searches that used the + boolean operator. (Bug #17280122)

4-way deadlock: zombies, purging binlogs, show processlist, show binlogs. (Bug #17283409)

When an SQL thread which was waiting for a commit lock was killed and restarted it caused a transaction to be skipped on worker. (Bug #17450876)

An InnoDB full-text search failure would occur due to an "unended" token. The string and string length should be passed for string comparison. (Bug #17659310)

Large numbers of partitioned InnoDB tables could consume much more memory when used in MySQL 5.6 or 5.7 than the memory used by the same tables used in previous releases of the MySQL Server. (Bug #17780517)

For full-text queries, a failure to check that num_token is less than max_proximity_item could result in an assertion. (Bug #18233051)

Certain queries for the INFORMATION_SCHEMA TABLES and COLUMNS tables could lead to excessive memory use when there were large numbers of empty InnoDB tables. (Bug #18592390)

When committing a transaction, a flag is now used to check whether a thread has been created, rather than checking the thread itself, which uses more resources, particularly when running the server with master_info_repository=TABLE. (Bug #18684222)

If a client thread on a worker executed FLUSH TABLES WITH READ LOCK while the master executed a DML, executing SHOW SLAVE STATUS in the same client became blocked, causing a deadlock. (Bug #19843808)

Ordering by a GROUP_CONCAT() result could cause a server exit. (Bug #19880368)

InnoDB databases with names beginning with a digit cause a full-text search (FTS) parser error. (Bug #17607956)

InnoDB full-text searches fail in databases whose names began with a digit. (Bug #17161372)

For InnoDB databases on Windows, the full-text search (FTS) object ID is not in the expected hexadecimal format. (Bug #16559254)

A code regression introduced in MySQL 5.6 negatively impacted DROP TABLE and ALTER TABLE performance. This could cause a performance drop between MySQL Server 5.5.x and 5.6.x. (Bug #16864741)