2020 Changelog

#### Experimental Feature[​](#experimental-feature-1 "Direct link to Experimental Feature")

- New functions `encrypt`, `aes_encrypt_mysql`, `decrypt`, `aes_decrypt_mysql`. These functions are working slowly, so we consider it as an experimental feature. [#11844](https://github.com/ClickHouse/ClickHouse/pull/11844) ([Vasily Nemkov](https://github.com/Enmk)).

#### Bug Fix[​](#bug-fix-6 "Direct link to Bug Fix")

- Mask password in data\_path in the `system.distribution_queue`. [#16727](https://github.com/ClickHouse/ClickHouse/pull/16727) ([Azat Khuzhin](https://github.com/azat)).
- Fix `IN` operator over several columns and tuples with enabled `transform_null_in` setting. Fixes [#15310](https://github.com/ClickHouse/ClickHouse/issues/15310). [#16722](https://github.com/ClickHouse/ClickHouse/pull/16722) ([Anton Popov](https://github.com/CurtizJ)).
- The setting `max_parallel_replicas` worked incorrectly if the queried table has no sampling. This fixes [#5733](https://github.com/ClickHouse/ClickHouse/issues/5733). [#16675](https://github.com/ClickHouse/ClickHouse/pull/16675) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Fix optimize\_read\_in\_order/optimize\_aggregation\_in\_order with max\_threads > 0 and expression in ORDER BY. [#16637](https://github.com/ClickHouse/ClickHouse/pull/16637) ([Azat Khuzhin](https://github.com/azat)).
- Calculation of `DEFAULT` expressions was involving possible name collisions (that was very unlikely to encounter). This fixes [#9359](https://github.com/ClickHouse/ClickHouse/issues/9359). [#16612](https://github.com/ClickHouse/ClickHouse/pull/16612) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Fix `query_thread_log.query_duration_ms` unit. [#16563](https://github.com/ClickHouse/ClickHouse/pull/16563) ([Azat Khuzhin](https://github.com/azat)).
- Fix a bug when using MySQL Master -> MySQL Slave -> ClickHouse MaterializeMySQL Engine. `MaterializeMySQL` is an experimental feature. [#16504](https://github.com/ClickHouse/ClickHouse/pull/16504) ([TCeason](https://github.com/TCeason)).
- Specifically crafted argument of `round` function with `Decimal` was leading to integer division by zero. This fixes [#13338](https://github.com/ClickHouse/ClickHouse/issues/13338). [#16451](https://github.com/ClickHouse/ClickHouse/pull/16451) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Fix DROP TABLE for Distributed (racy with INSERT). [#16409](https://github.com/ClickHouse/ClickHouse/pull/16409) ([Azat Khuzhin](https://github.com/azat)).
- Fix processing of very large entries in replication queue. Very large entries may appear in ALTER queries if table structure is extremely large (near 1 MB). This fixes [#16307](https://github.com/ClickHouse/ClickHouse/issues/16307). [#16332](https://github.com/ClickHouse/ClickHouse/pull/16332) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Fixed the inconsistent behaviour when a part of return data could be dropped because the set for its filtration wasn't created. [#16308](https://github.com/ClickHouse/ClickHouse/pull/16308) ([Nikita Mikhaylov](https://github.com/nikitamikhaylov)).
- Fix dictGet in sharding\_key (and similar places, i.e. when the function context is stored permanently). [#16205](https://github.com/ClickHouse/ClickHouse/pull/16205) ([Azat Khuzhin](https://github.com/azat)).
- Fix the exception thrown in `clickhouse-local` when trying to execute `OPTIMIZE` command. Fixes [#16076](https://github.com/ClickHouse/ClickHouse/issues/16076). [#16192](https://github.com/ClickHouse/ClickHouse/pull/16192) ([filimonov](https://github.com/filimonov)).
- Fixes [#15780](https://github.com/ClickHouse/ClickHouse/issues/15780) regression, e.g. `indexOf([1, 2, 3], toLowCardinality(1))` now is prohibited but it should not be. [#16038](https://github.com/ClickHouse/ClickHouse/pull/16038) ([Mike](https://github.com/myrrc)).
- Fix bug with MySQL database. When MySQL server used as database engine is down some queries raise Exception, because they try to get tables from disabled server, while it's unnecessary. For example, query `SELECT ... FROM system.parts` should work only with MergeTree tables and don't touch MySQL database at all. [#16032](https://github.com/ClickHouse/ClickHouse/pull/16032) ([Kruglov Pavel](https://github.com/Avogar)).
- Now exception will be thrown when `ALTER MODIFY COLUMN ... DEFAULT ...` has incompatible default with column type. Fixes [#15854](https://github.com/ClickHouse/ClickHouse/issues/15854). [#15858](https://github.com/ClickHouse/ClickHouse/pull/15858) ([alesapin](https://github.com/alesapin)).
- Fixed IPv4CIDRToRange/IPv6CIDRToRange functions to accept const IP-column values. [#15856](https://github.com/ClickHouse/ClickHouse/pull/15856) ([vladimir-golovchenko](https://github.com/vladimir-golovchenko)).

#### Improvement[​](#improvement-2 "Direct link to Improvement")