2020 Changelog

- Enable `use_compact_format_in_distributed_parts_names` by default (see the documentation for the reference). [#16728](https://github.com/ClickHouse/ClickHouse/pull/16728) ([Azat Khuzhin](https://github.com/azat)).
- Accept user settings related to file formats (e.g. `format_csv_delimiter`) in the `SETTINGS` clause when creating a table that uses `File` engine, and use these settings in all `INSERT`s and `SELECT`s. The file format settings changed in the current user session, or in the `SETTINGS` clause of a DML query itself, no longer affect the query. [#16591](https://github.com/ClickHouse/ClickHouse/pull/16591) ([Alexander Kuzmenkov](https://github.com/akuzm)).

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

- add `*.xz` compression/decompression support.It enables using `*.xz` in `file()` function. This closes [#8828](https://github.com/ClickHouse/ClickHouse/issues/8828). [#16578](https://github.com/ClickHouse/ClickHouse/pull/16578) ([Abi Palagashvili](https://github.com/fibersel)).
- Introduce the query `ALTER TABLE ... DROP|DETACH PART 'part_name'`. [#15511](https://github.com/ClickHouse/ClickHouse/pull/15511) ([nvartolomei](https://github.com/nvartolomei)).
- Added new ALTER UPDATE/DELETE IN PARTITION syntax. [#13403](https://github.com/ClickHouse/ClickHouse/pull/13403) ([Vladimir Chebotarev](https://github.com/excitoon)).
- Allow formatting named tuples as JSON objects when using JSON input/output formats, controlled by the `output_format_json_named_tuples_as_objects` setting, disabled by default. [#17175](https://github.com/ClickHouse/ClickHouse/pull/17175) ([Alexander Kuzmenkov](https://github.com/akuzm)).
- Add a possibility to input enum value as it's id in TSV and CSV formats by default. [#16834](https://github.com/ClickHouse/ClickHouse/pull/16834) ([Kruglov Pavel](https://github.com/Avogar)).
- Add COLLATE support for Nullable, LowCardinality, Array and Tuple, where nested type is String. Also refactor the code associated with collations in ColumnString.cpp. [#16273](https://github.com/ClickHouse/ClickHouse/pull/16273) ([Kruglov Pavel](https://github.com/Avogar)).
- New `tcpPort` function returns TCP port listened by this server. [#17134](https://github.com/ClickHouse/ClickHouse/pull/17134) ([Ivan](https://github.com/abyss7)).
- Add new math functions: `acosh`, `asinh`, `atan2`, `atanh`, `cosh`, `hypot`, `log1p`, `sinh`. [#16636](https://github.com/ClickHouse/ClickHouse/pull/16636) ([Konstantin Malanchev](https://github.com/hombit)).
- Possibility to distribute the merges between different replicas. Introduces the `execute_merges_on_single_replica_time_threshold` mergetree setting. [#16424](https://github.com/ClickHouse/ClickHouse/pull/16424) ([filimonov](https://github.com/filimonov)).
- Add setting `aggregate_functions_null_for_empty` for SQL standard compatibility. This option will rewrite all aggregate functions in a query, adding -OrNull suffix to them. Implements [10273](https://github.com/ClickHouse/ClickHouse/issues/10273). [#16123](https://github.com/ClickHouse/ClickHouse/pull/16123) ([flynn](https://github.com/ucasFL)).
- Updated DateTime, DateTime64 parsing to accept string Date literal format. [#16040](https://github.com/ClickHouse/ClickHouse/pull/16040) ([Maksim Kita](https://github.com/kitaisreal)).
- Make it possible to change the path to history file in `clickhouse-client` using the `--history_file` parameter. [#15960](https://github.com/ClickHouse/ClickHouse/pull/15960) ([Maksim Kita](https://github.com/kitaisreal)).

#### Bug Fix[​](#bug-fix-2 "Direct link to Bug Fix")