2020 Changelog

### ClickHouse release v20.9.6.14-stable, 2020-11-20[​](#clickhouse-release-v209614-stable-2020-11-20 "Direct link to ClickHouse release v20.9.6.14-stable, 2020-11-20")

#### Improvement[​](#improvement-5 "Direct link to Improvement")

- Make it possible to connect to `clickhouse-server` secure endpoint which requires SNI. This is possible when `clickhouse-server` is hosted behind TLS proxy. [#16938](https://github.com/ClickHouse/ClickHouse/pull/16938) ([filimonov](https://github.com/filimonov)).
- Conditional aggregate functions (for example: `avgIf`, `sumIf`, `maxIf`) should return `NULL` when miss rows and use nullable arguments. [#13964](https://github.com/ClickHouse/ClickHouse/pull/13964) ([Winter Zhang](https://github.com/zhang2014)).

#### Bug Fix[​](#bug-fix-11 "Direct link to Bug Fix")

- Fix bug when `ON CLUSTER` queries may hang forever for non-leader ReplicatedMergeTreeTables. [#17089](https://github.com/ClickHouse/ClickHouse/pull/17089) ([alesapin](https://github.com/alesapin)).
- Reresolve the IP of the `format_avro_schema_registry_url` in case of errors. [#16985](https://github.com/ClickHouse/ClickHouse/pull/16985) ([filimonov](https://github.com/filimonov)).
- Fix possible server crash after `ALTER TABLE ... MODIFY COLUMN ... NewType` when `SELECT` have `WHERE` expression on altering column and alter does not finished yet. [#16968](https://github.com/ClickHouse/ClickHouse/pull/16968) ([Amos Bird](https://github.com/amosbird)).
- Install script should always create subdirs in config folders. This is only relevant for Docker build with custom config. [#16936](https://github.com/ClickHouse/ClickHouse/pull/16936) ([filimonov](https://github.com/filimonov)).
- Fix possible error `Illegal type of argument` for queries with `ORDER BY`. Fixes [#16580](https://github.com/ClickHouse/ClickHouse/issues/16580). [#16928](https://github.com/ClickHouse/ClickHouse/pull/16928) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).
- Abort multipart upload if no data was written to WriteBufferFromS3. [#16840](https://github.com/ClickHouse/ClickHouse/pull/16840) ([Pavel Kovalenko](https://github.com/Jokser)).
- Fix crash when using `any` without any arguments. This is for [#16803](https://github.com/ClickHouse/ClickHouse/issues/16803) . cc @azat. [#16826](https://github.com/ClickHouse/ClickHouse/pull/16826) ([Amos Bird](https://github.com/amosbird)).
- 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)).
- This will 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)).
- fixes [#16574](https://github.com/ClickHouse/ClickHouse/issues/16574) fixes [#16231](https://github.com/ClickHouse/ClickHouse/issues/16231) fix remote query failure when using 'if' suffix aggregate function. [#16610](https://github.com/ClickHouse/ClickHouse/pull/16610) ([Winter Zhang](https://github.com/zhang2014)).
- Query is finished faster in case of exception. Cancel execution on remote replicas if exception happens. [#15578](https://github.com/ClickHouse/ClickHouse/pull/15578) ([Azat Khuzhin](https://github.com/azat)).

### ClickHouse release v20.9.5.5-stable, 2020-11-13[​](#clickhouse-release-v20955-stable-2020-11-13 "Direct link to ClickHouse release v20.9.5.5-stable, 2020-11-13")

#### Bug Fix[​](#bug-fix-12 "Direct link to Bug Fix")

- Fix rare silent crashes when query profiler is on and ClickHouse is installed on OS with glibc version that has (supposedly) broken asynchronous unwind tables for some functions. This fixes [#15301](https://github.com/ClickHouse/ClickHouse/issues/15301). This fixes [#13098](https://github.com/ClickHouse/ClickHouse/issues/13098). [#16846](https://github.com/ClickHouse/ClickHouse/pull/16846) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Now when parsing AVRO from input the LowCardinality is removed from type. Fixes [#16188](https://github.com/ClickHouse/ClickHouse/issues/16188). [#16521](https://github.com/ClickHouse/ClickHouse/pull/16521) ([Mike](https://github.com/myrrc)).
- Fix rapid growth of metadata when using MySQL Master -> MySQL Slave -> ClickHouse MaterializeMySQL Engine, and `slave_parallel_worker` enabled on MySQL Slave, by properly shrinking GTID sets. This fixes [#15951](https://github.com/ClickHouse/ClickHouse/issues/15951). [#16504](https://github.com/ClickHouse/ClickHouse/pull/16504) ([TCeason](https://github.com/TCeason)).
- 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 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)).

### ClickHouse release v20.9.4.76-stable (2020-10-29)[​](#clickhouse-release-v209476-stable-2020-10-29 "Direct link to ClickHouse release v20.9.4.76-stable (2020-10-29)")

#### Bug Fix[​](#bug-fix-13 "Direct link to Bug Fix")