Log Message:
mysql57: updated to 5.7.33

Changes in MySQL 5.7.33

Optimizer Notes

MySQL attempts to use an ordered index for any ORDER BY or GROUP BY query that \ 
has a LIMIT clause, overriding any other choices made by the optimizer, whenever \ 
it determines that this would result in faster execution. Because the algorithm \ 
for making this determination makes certain assumptions about data distribution \ 
and other conditions, it may not always be completely correct, and it is \ 
possible in some cases that choosing a different optimization for such queries \ 
can provide better performance. To handle such occurrences, it is now possible \ 
to disable this optimization by setting the optimizer_switch system variable's \ 
prefer_ordering_index flag to off.

For more information about this flag and examples of its use, see Switchable \ 
Optimizations, and LIMIT Query Optimization.

Our thanks to Jeremy Cole for the contribution.
Security Notes

The linked OpenSSL library for MySQL Server has been updated to version 1.1.1i. \ 
Issues fixed in the new OpenSSL version are described at \ 
https://www.openssl.org/news/cl111.txt and \ 
https://www.openssl.org/news/vulnerabilities.html.

Functionality Added or Changed

When invoked with the --all-databases option, mysqldump now dumps the mysql \ 
database first, so that when the dump file is reloaded, any accounts named in \ 
the DEFINER clause of other objects will already have been created.

Bugs Fixed

InnoDB: The full-text search synchronization thread attempted to read a \ 
previously-freed word from the index cache.

InnoDB: Calls to numa_all_nodes_ptr were replaced by the numa_get_mems_allowed() \ 
function. Thanks to Daniel Black for the contribution.

Replication: When the system variable transaction_write_set_extraction=XXHASH64 \ 
is set, which is the default in MySQL 8.0 and a requirement for Group \ 
Replication, the collection of writes for a transaction previously had no upper \ 
size limit. Now, for standard source to replica replication, the numeric limit \ 
on write sets specified by binlog_transaction_dependency_history_size is \ 
applied, after which the write set information is discarded but the transaction \ 
continues to execute. Because the write set information is then unavailable for \ 
the dependency calculation, the transaction is marked as non-concurrent, and is \ 
processed sequentially on the replica. For Group Replication, the process of \ 
extracting the writes from a transaction is required for conflict detection and \ 
certification on all group members, so the write set information cannot be \ 
discarded if the transaction is to complete. The byte limit set by \ 
group_replication_transaction_size_limit is applied instead of the nu
meric limit, and if the limit is exceeded, the transaction fails to execute.

Replication: As the number of replicas replicating from a semisynchronous source \ 
server increased, locking contention could result in a performance degradation. \ 
The locking mechanisms used by the plugins have been changed to use shared locks \ 
where possible, avoid unnecessary lock acquisitions, and limit callbacks. The \ 
new behaviors can be implemented by enabling the following system variables:

replication_sender_observe_commit_only=1 limits callbacks.

replication_optimize_for_static_plugin_config=1 adds shared locks and avoids \ 
unnecessary lock acquisitions. This system variable must be disabled if you want \ 
to uninstall the plugin.

Both system variables can be enabled before or after installing the \ 
semisynchronous replication plugin, and can be enabled while replication is \ 
running. Semisynchronous replication source servers can also get performance \ 
benefits from enabling these system variables, because they use the same locking \ 
mechanisms as the replicas.

Replication: On a multi-threaded replica where the commit order is preserved, \ 
worker threads must wait for all transactions that occur earlier in the relay \ 
log to commit before committing their own transactions. If a deadlock occurs \ 
because a thread waiting to commit a transaction later in the commit order has \ 
locked rows needed by a transaction earlier in the commit order, a deadlock \ 
detection algorithm signals the waiting thread to roll back its transaction. \ 
Previously, if transaction retries were not available, the worker thread that \ 
rolled back its transaction would exit immediately without signalling other \ 
worker threads in the commit order, which could stall replication. A worker \ 
thread in this situation now waits for its turn to call the rollback function, \ 
which means it signals the other threads correctly.

Replication: GTIDs are only available on a server instance up to the number of \ 
non-negative values for a signed 64-bit integer (2 to the power of 63 minus 1). \ 
If you set the value of gtid_purged to a number that approaches this limit, \ 
subsequent commits can cause the server to run out of GTIDs and take the action \ 
specified by binlog_error_action. From MySQL 8.0.23, a warning message is issued \ 
when the server instance is approaching the limit.

Microsoft Windows: On Windows, running the MySQL server as a service caused \ 
shared-memory connections to fail.

The server did not handle all cases of the WHERE_CONDITION optimization correctly.

For the engines which support primary key extension, when the total key length \ 
exceeded MAX_KEY_LENGTH or the number of key parts exceeded MAX_REF_PARTS, key \ 
parts of primary keys which did not fit within these limits were not added to \ 
the secondary key, but key parts of primary keys were unconditionally marked as \ 
part of secondary keys.

This led to a situation in which the secondary key was treated as a covering \ 
index, which meant sometimes the wrong access method was chosen.

This is fixed by modifying the way in which key parts of primary keys are added \ 
to secondary keys so that those which do not fit within which do not fit within \ 
the limits mentioned previously mentioned are cleared.

Privileges for some INFORMATION_SCHEMA tables were checked incorrectly.

In certain cases, the server did not handle multiply-nested subqueries correctly.

Certain accounts could cause server startup failure if the skip_name_resolve \ 
system variable was enabled.

Client programs could unexpectedly exit if communication packets contained bad data.

A buffer overflow in the client library was fixed.

mysql_config_editor incorrectly treated # in password values as a comment character.