> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/release-notes/enterprise-server/old-releases/10.2/10.2.31-6.md).

# Release Notes for MariaDB Enterprise Server 10.2.31-6

This sixth release of [MariaDB Enterprise Server 10.2](/docs/release-notes/enterprise-server/old-releases/10.2.md) is a maintenance release, including a variety of fixes.

MariaDB Enterprise Server 10.2.31-6 was released on 2020-03-02.

## Fixed Security Vulnerabilities

| CVE (with [cve.org](https://www.cve.org) link)                                | CVSS base score |
| ----------------------------------------------------------------------------- | --------------- |
| [CVE-2020-2574](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-2574) | 5.9             |

## Notable Changes

* The systemd start and stop timeout for the MariaDB service is now set to 900 seconds (15 minutes). ([MDEV-17571](https://jira.mariadb.org/browse/MDEV-17571))
* For [MariaDB Enterprise Cluster](https://mariadb.com/docs/galera-cluster/) (Galera Library 25.3.29):
  * Setting [socket.recv\_buf\_size](/docs/galera-cluster/reference/wsrep-variable-details/wsrep_provider_options.md#socketrecv_buf_size) was not effective because it was done after the socket was connected or accepted. The default value also caused TCP receive buffer auto-tuning to be disabled. This lead to sub-optimal performance in high bandwidth WAN clusters. The default value for [socket.recv\_buf\_size](/docs/galera-cluster/reference/wsrep-variable-details/wsrep_provider_options.md#socketrecv_buf_size) has been changed to auto, which lets the kernel tune the TCP receive buffer. A new variable `socket.send_buf_size` with default value `auto` was added to allow send buffer tuning.

## Issues Fixed

### Can result in data loss

* An `ALTER TABLE ... RENAME` could fail without an error and result in a dropped table. (MENT-416)

### Can result in a hang or crash

* During a server restart [InnoDB](/docs/server/server-usage/storage-engines/innodb.md) recovery could encounter an out-of-memory condition. A restart was only possible after increasing [innodb\_buffer\_pool\_size](/docs/server/server-usage/storage-engines/innodb/innodb-buffer-pool.md#innodb_buffer_pool_size) . ([MDEV-19176](https://jira.mariadb.org/browse/MDEV-19176))
* On a rollback of a large insert or update, or during a background task to purge transaction history after a large update or delete, the server could hang. ([MDEV-21509](https://jira.mariadb.org/browse/MDEV-21509))
* On a rollback or during a background task to purge transaction history due to a `SPATIAL INDEX`, the server could hang. ([MDEV-21512](https://jira.mariadb.org/browse/MDEV-21512))
* Crashes could occur rarely when using `ALTER TABLE ... IMPORT TABLESPACE` ([MDEV-21513](https://jira.mariadb.org/browse/MDEV-21513))
* Possible server crash if [binlog\_checksum=CRC32](/docs/server/ha-and-performance/standard-replication/binlog-event-checksums.md) (default) is set and if the value for parameter `pos` in [SHOW BINLOG EVENTS FROM pos](/docs/server/reference/sql-statements/administrative-sql-statements/show/show-binlog-events.md) does not point to the beginning of an event in the binary log. ([MDEV-18046](https://jira.mariadb.org/browse/MDEV-18046))
* A replication primary (master) running in semi-sync mode could crash when [RESET MASTER](/docs/server/reference/sql-statements/administrative-sql-statements/replication-statements/reset-master.md) is executed and the replica reconnects using the GTID protocol. ([MDEV-19376](https://jira.mariadb.org/browse/MDEV-19376))
* [MariaDB Enterprise Backup](/docs/server/server-usage/backup-and-restore/mariadb-enterprise-backup.md) could encounter a deadlock if a backup is taken from a replica with [slave-parallel-threads](/docs/server/server-management/variables-and-modes/server-system-variables.md#slave_parallel_threads) is set to a value greater than `0` ([MDEV-21255](https://jira.mariadb.org/browse/MDEV-21255))
* [MariaDB Enterprise Backup](/docs/server/server-usage/backup-and-restore/mariadb-enterprise-backup.md) could crash when used in combination with `FLUSH TABLES` and `UNLOCK TABLES` (MENT-438)
* The `aria_pack` utility crashed when running an offline datafile compress on a table. ([MDEV-14183](https://jira.mariadb.org/browse/MDEV-14183))
* Dropping a partition with [wsrep\_OSU\_method=RSU](/docs/server/server-management/variables-and-modes/server-system-variables.md#wsrep_OSU_method) and SESSION [sql\_log\_bin=0](/docs/server/ha-and-performance/standard-replication/replication-and-binary-log-system-variables.md#sql_log_bin) caused the [MariaDB Enterprise Cluster](https://mariadb.com/docs/galera-cluster/) (Galera) node to hang. ([MDEV-21189](https://jira.mariadb.org/browse/MDEV-21189))

### Can result in unexpected behavior

* Executing [TRUNCATE](/docs/server/reference/sql-statements/table-statements/truncate-table.md) or [OPTIMIZE](/docs/server/ha-and-performance/optimization-and-tuning/optimizing-tables/optimize-table.md) on [InnoDB](/docs/server/server-usage/storage-engines/innodb.md) tables could lead to an unexpected `SQL Error (1118): Row size too large`, when [innodb\_strict\_mode=ON](/docs/server/server-management/variables-and-modes/server-system-variables.md#innodb_strict_mode) (default). ([MDEV-21429](https://jira.mariadb.org/browse/MDEV-21429))
* Queries which use window functions and implicit grouping could return wrong results. ([MDEV-21318](https://jira.mariadb.org/browse/MDEV-21318))
* Queries which use `DISTINCT COUNT(*) OVER()` in the expression returned wrong results. ([MDEV-16579](https://jira.mariadb.org/browse/MDEV-16579))
* Inefficient thread handling in the thread pool, impacting any application that uses the thread pool. ([MDEV-21343](https://jira.mariadb.org/browse/MDEV-21343))
* The MariaDB Enterprise Server config file `mariadb-enterprise.cnf` was not registered as a config file in RPM packages. (MENT-591)
* `ALTER USER IF EXISTS` generated a SQL syntax error. (MENT-643)
* A query using `GROUP BY` with an expression containing a field of a view could return wrong results. ([MDEV-20922](https://jira.mariadb.org/browse/MDEV-20922))
* Running the script `mysql_tzinfo_to_sql` for MariaDB Enterprise Cluster could result in inconsistent timezone information across different nodes. ([MDEV-21209](https://jira.mariadb.org/browse/MDEV-21209))
* Using the --use-memory option with [mariadb-backup](/docs/server/server-usage/backup-and-restore/mariadb-backup.md) would cause it to run out of memory. ([MDEV-20679](https://jira.mariadb.org/browse/MDEV-20679))
* For [MariaDB Enterprise Cluster](https://mariadb.com/docs/galera-cluster/) (Galera Library 25.3.29):
  * GCS delivered a JOIN message even if the node was in a DONOR state.
  * GCache could contain mixed histories from different clusters.
  * GComm socket timestamping/liveness checking produced false positives during replication of large transactions, which caused excessive amounts of broken connections.
  * Large transactions were able to monopolize bandwidth when segmentation was configured, causing delayed in messages relayed by segment representative. The fix implements fair queuing of messages.
  * Due to a bug in quorum computation, two primary conflicting primary components were formed when the group merged and partitioned again while the new primary view was forming.

## Related to installation or upgrade

* Server could not be started when [lc\_messages](/docs/server/server-management/variables-and-modes/server-system-variables.md#lc_messages) is set in a config file. (MENT-625)

## Interface Changes

* [innodb\_spin\_wait\_delay](/docs/server/server-usage/storage-engines/innodb/innodb-system-variables.md) system variable default value changed from `6` to `4`, matching the default of MariaDB Enterprise Server 10.4 and 10.3.

## Platforms

In alignment with the [enterprise lifecycle](/docs/release-notes/enterprise-server/about/enterprise-server-lifecycle.md), MariaDB Enterprise Server 10.2.31-6 is provided for:

* Red Hat Enterprise Linux 8
* Red Hat Enterprise Linux 7
* Red Hat Enterprise Linux 6
* CentOS 8
* CentOS 7
* CentOS 6
* Ubuntu 18.04
* Ubuntu 16.04
* Debian 10
* Debian 9
* Debian 8
* SUSE Linux Enterprise Server 15
* SUSE Linux Enterprise Server 12
* Microsoft Windows

Some components of MariaDB Enterprise Server might not support all platforms. For additional information, see "[MariaDB Corporation Engineering Policies](https://mariadb.com/engineering-policies)".

#### Note

CentOS 6, Debian 8, and Red Hat Enterprise Linux 6 are no longer supported as per the [MariaDB Engineering Policy](https://mariadb.com/engineering-policies). Older releases are available from the [MariaDB Downloads page](https://mariadb.com/downloads/). Instructions for installation are included as a `README` file within the download.

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