2021 Changelog

#### New Feature[​](#new-feature-7 "Direct link to New Feature")

- Extended range of `DateTime64` to support dates from year 1925 to 2283. Improved support of `DateTime` around zero date (`1970-01-01`). [#9404](https://github.com/ClickHouse/ClickHouse/pull/9404) ([alexey-milovidov](https://github.com/alexey-milovidov), [Vasily Nemkov](https://github.com/Enmk)). Not every time and date functions are working for extended range of dates.
- Added support of Kerberos authentication for preconfigured users and HTTP requests (GSS-SPNEGO). [#14995](https://github.com/ClickHouse/ClickHouse/pull/14995) ([Denis Glazachev](https://github.com/traceon)).
- Add `prefer_column_name_to_alias` setting to use original column names instead of aliases. it is needed to be more compatible with common databases' aliasing rules. This is for [#9715](https://github.com/ClickHouse/ClickHouse/issues/9715) and [#9887](https://github.com/ClickHouse/ClickHouse/issues/9887). [#22044](https://github.com/ClickHouse/ClickHouse/pull/22044) ([Amos Bird](https://github.com/amosbird)).
- Added functions `dictGetChildren(dictionary, key)`, `dictGetDescendants(dictionary, key, level)`. Function `dictGetChildren` return all children as an array if indexes. It is a inverse transformation for `dictGetHierarchy`. Function `dictGetDescendants` return all descendants as if `dictGetChildren` was applied `level` times recursively. Zero `level` value is equivalent to infinity. Closes [#14656](https://github.com/ClickHouse/ClickHouse/issues/14656). [#22096](https://github.com/ClickHouse/ClickHouse/pull/22096) ([Maksim Kita](https://github.com/kitaisreal)).
- Added `executable_pool` dictionary source. Close [#14528](https://github.com/ClickHouse/ClickHouse/issues/14528). [#21321](https://github.com/ClickHouse/ClickHouse/pull/21321) ([Maksim Kita](https://github.com/kitaisreal)).
- Added table function `dictionary`. It works the same way as `Dictionary` engine. Closes [#21560](https://github.com/ClickHouse/ClickHouse/issues/21560). [#21910](https://github.com/ClickHouse/ClickHouse/pull/21910) ([Maksim Kita](https://github.com/kitaisreal)).
- Support `Nullable` type for `PolygonDictionary` attribute. [#21890](https://github.com/ClickHouse/ClickHouse/pull/21890) ([Maksim Kita](https://github.com/kitaisreal)).
- Functions `dictGet`, `dictHas` use current database name if it is not specified for dictionaries created with DDL. Closes [#21632](https://github.com/ClickHouse/ClickHouse/issues/21632). [#21859](https://github.com/ClickHouse/ClickHouse/pull/21859) ([Maksim Kita](https://github.com/kitaisreal)).
- Added function `dictGetOrNull`. It works like `dictGet`, but return `Null` in case key was not found in dictionary. Closes [#22375](https://github.com/ClickHouse/ClickHouse/issues/22375). [#22413](https://github.com/ClickHouse/ClickHouse/pull/22413) ([Maksim Kita](https://github.com/kitaisreal)).
- Added async update in `ComplexKeyCache`, `SSDCache`, `SSDComplexKeyCache` dictionaries. Added support for `Nullable` type in `Cache`, `ComplexKeyCache`, `SSDCache`, `SSDComplexKeyCache` dictionaries. Added support for multiple attributes fetch with `dictGet`, `dictGetOrDefault` functions. Fixes [#21517](https://github.com/ClickHouse/ClickHouse/issues/21517). [#20595](https://github.com/ClickHouse/ClickHouse/pull/20595) ([Maksim Kita](https://github.com/kitaisreal)).
- Support `dictHas` function for `RangeHashedDictionary`. Fixes [#6680](https://github.com/ClickHouse/ClickHouse/issues/6680). [#19816](https://github.com/ClickHouse/ClickHouse/pull/19816) ([Maksim Kita](https://github.com/kitaisreal)).
- Add function `timezoneOf` that returns the timezone name of `DateTime` or `DateTime64` data types. This does not close [#9959](https://github.com/ClickHouse/ClickHouse/issues/9959). Fix inconsistencies in function names: add aliases `timezone` and `timeZone` as well as `toTimezone` and `toTimeZone` and `timezoneOf` and `timeZoneOf`. [#22001](https://github.com/ClickHouse/ClickHouse/pull/22001) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Add new optional clause `GRANTEES` for `CREATE/ALTER USER` commands. It specifies users or roles which are allowed to receive grants from this user on condition this user has also all required access granted with grant option. By default `GRANTEES ANY` is used which means a user with grant option can grant to anyone. Syntax: `CREATE USER ... GRANTEES {user | role | ANY | NONE} [,...] [EXCEPT {user | role} [,...]]`. [#21641](https://github.com/ClickHouse/ClickHouse/pull/21641) ([Vitaly Baranov](https://github.com/vitlibar)).
- Add new column `slowdowns_count` to `system.clusters`. When using hedged requests, it shows how many times we switched to another replica because this replica was responding slowly. Also show actual value of `errors_count` in `system.clusters`. [#21480](https://github.com/ClickHouse/ClickHouse/pull/21480) ([Kruglov Pavel](https://github.com/Avogar)).
- Add `_partition_id` virtual column for `MergeTree*` engines. Allow to prune partitions by `_partition_id`. Add `partitionID()` function to calculate partition id string. [#21401](https://github.com/ClickHouse/ClickHouse/pull/21401) ([Amos Bird](https://github.com/amosbird)).
- Add function `isIPAddressInRange` to test if an IPv4 or IPv6 address is contained in a given CIDR network prefix. [#21329](https://github.com/ClickHouse/ClickHouse/pull/21329) ([PHO](https://github.com/depressed-pho)).
- Added new SQL command `ALTER TABLE 'table_name' UNFREEZE [PARTITION 'part_expr'] WITH NAME 'backup_name'`. This command is needed to properly remove 'freezed' partitions from all disks. [#21142](https://github.com/ClickHouse/ClickHouse/pull/21142) ([Pavel Kovalenko](https://github.com/Jokser)).
- Supports implicit key type conversion for JOIN. [#19885](https://github.com/ClickHouse/ClickHouse/pull/19885) ([Vladimir](https://github.com/vdimir)).

#### Experimental Feature[​](#experimental-feature-6 "Direct link to Experimental Feature")

- Support `RANGE OFFSET` frame (for window functions) for floating point types. Implement `lagInFrame`/`leadInFrame` window functions, which are analogous to `lag`/`lead`, but respect the window frame. They are identical when the frame is `between unbounded preceding and unbounded following`. This closes [#5485](https://github.com/ClickHouse/ClickHouse/issues/5485). [#21895](https://github.com/ClickHouse/ClickHouse/pull/21895) ([Alexander Kuzmenkov](https://github.com/akuzm)).
- Zero-copy replication for `ReplicatedMergeTree` over S3 storage. [#16240](https://github.com/ClickHouse/ClickHouse/pull/16240) ([ianton-ru](https://github.com/ianton-ru)).
- Added possibility to migrate existing S3 disk to the schema with backup-restore capabilities. [#22070](https://github.com/ClickHouse/ClickHouse/pull/22070) ([Pavel Kovalenko](https://github.com/Jokser)).

#### Performance Improvement[​](#performance-improvement-7 "Direct link to Performance Improvement")