2020 Changelog

- `TTL DELETE WHERE` and `TTL GROUP BY` for automatic data coarsening and rollup in tables. [#10537](https://github.com/ClickHouse/ClickHouse/pull/10537) ([expl0si0nn](https://github.com/expl0si0nn)).
- Implementation of PostgreSQL wire protocol. [#10242](https://github.com/ClickHouse/ClickHouse/pull/10242) ([Movses](https://github.com/MovElb)).
- Added system tables for users, roles, grants, settings profiles, quotas, row policies; added commands SHOW USER, SHOW [CURRENT|ENABLED] ROLES, SHOW SETTINGS PROFILES. [#10387](https://github.com/ClickHouse/ClickHouse/pull/10387) ([Vitaly Baranov](https://github.com/vitlibar)).
- Support writes in ODBC Table function [#10554](https://github.com/ClickHouse/ClickHouse/pull/10554) ([ageraab](https://github.com/ageraab)). [#10901](https://github.com/ClickHouse/ClickHouse/pull/10901) ([tavplubix](https://github.com/tavplubix)).
- Add query performance metrics based on Linux `perf_events` (these metrics are calculated with hardware CPU counters and OS counters). It is optional and requires `CAP_SYS_ADMIN` to be set on clickhouse binary. [#9545](https://github.com/ClickHouse/ClickHouse/pull/9545) [Andrey Skobtsov](https://github.com/And42). [#11226](https://github.com/ClickHouse/ClickHouse/pull/11226) ([Alexander Kuzmenkov](https://github.com/akuzm)).
- Now support `NULL` and `NOT NULL` modifiers for data types in `CREATE` query. [#11057](https://github.com/ClickHouse/ClickHouse/pull/11057) ([Павел Потемкин](https://github.com/Potya)).
- Add `ArrowStream` input and output format. [#11088](https://github.com/ClickHouse/ClickHouse/pull/11088) ([hcz](https://github.com/hczhcz)).
- Support Cassandra as external dictionary source. [#4978](https://github.com/ClickHouse/ClickHouse/pull/4978) ([favstovol](https://github.com/favstovol)).
- Added a new layout `direct` which loads all the data directly from the source for each query, without storing or caching data. [#10622](https://github.com/ClickHouse/ClickHouse/pull/10622) ([Artem Streltsov](https://github.com/kekekekule)).
- Added new `complex_key_direct` layout to dictionaries, that does not store anything locally during query execution. [#10850](https://github.com/ClickHouse/ClickHouse/pull/10850) ([Artem Streltsov](https://github.com/kekekekule)).
- Added support for MySQL style global variables syntax (stub). This is needed for compatibility of MySQL protocol. [#11832](https://github.com/ClickHouse/ClickHouse/pull/11832) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Added syntax highligting to `clickhouse-client` using `replxx`. [#11422](https://github.com/ClickHouse/ClickHouse/pull/11422) ([Tagir Kuskarov](https://github.com/kuskarov)).
- `minMap` and `maxMap` functions were added. [#11603](https://github.com/ClickHouse/ClickHouse/pull/11603) ([Ildus Kurbangaliev](https://github.com/ildus)).
- Add the `system.asynchronous_metric_log` table that logs historical metrics from `system.asynchronous_metrics`. [#11588](https://github.com/ClickHouse/ClickHouse/pull/11588) ([Alexander Kuzmenkov](https://github.com/akuzm)).
- Add functions `extractAllGroupsHorizontal(haystack, re)` and `extractAllGroupsVertical(haystack, re)`. [#11554](https://github.com/ClickHouse/ClickHouse/pull/11554) ([Vasily Nemkov](https://github.com/Enmk)).
- Add SHOW CLUSTER(S) queries. [#11467](https://github.com/ClickHouse/ClickHouse/pull/11467) ([hexiaoting](https://github.com/hexiaoting)).
- Add `netloc` function for extracting network location, similar to `urlparse(url)`, `netloc` in python. [#11356](https://github.com/ClickHouse/ClickHouse/pull/11356) ([Guillaume Tassery](https://github.com/YiuRULE)).
- Add 2 more virtual columns for engine=Kafka to access message headers. [#11283](https://github.com/ClickHouse/ClickHouse/pull/11283) ([filimonov](https://github.com/filimonov)).
- Add `_timestamp_ms` virtual column for Kafka engine (type is `Nullable(DateTime64(3))`). [#11260](https://github.com/ClickHouse/ClickHouse/pull/11260) ([filimonov](https://github.com/filimonov)).
- Add function `randomFixedString`. [#10866](https://github.com/ClickHouse/ClickHouse/pull/10866) ([Andrei Nekrashevich](https://github.com/xolm)).
- Add function `fuzzBits` that randomly flips bits in a string with given probability. [#11237](https://github.com/ClickHouse/ClickHouse/pull/11237) ([Andrei Nekrashevich](https://github.com/xolm)).
- Allow comparison of numbers with constant string in comparison operators, IN and VALUES sections. [#11647](https://github.com/ClickHouse/ClickHouse/pull/11647) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Add `round_robin` load\_balancing mode. [#11645](https://github.com/ClickHouse/ClickHouse/pull/11645) ([Azat Khuzhin](https://github.com/azat)).
- Add `cast_keep_nullable` setting. If set `CAST(something_nullable AS Type)` return `Nullable(Type)`. [#11733](https://github.com/ClickHouse/ClickHouse/pull/11733) ([Artem Zuikov](https://github.com/4ertus2)).
- Added column `position` to `system.columns` table and `column_position` to `system.parts_columns` table. It contains ordinal position of a column in a table starting with 1. This closes [#7744](https://github.com/ClickHouse/ClickHouse/issues/7744). [#11655](https://github.com/ClickHouse/ClickHouse/pull/11655) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- ON CLUSTER support for SYSTEM `{FLUSH DISTRIBUTED,STOP/START DISTRIBUTED SEND}`. [#11415](https://github.com/ClickHouse/ClickHouse/pull/11415) ([Azat Khuzhin](https://github.com/azat)).
- Add system.distribution\_queue table. [#11394](https://github.com/ClickHouse/ClickHouse/pull/11394) ([Azat Khuzhin](https://github.com/azat)).
- Support for all format settings in Kafka, expose some setting on table level, adjust the defaults for better performance. [#11388](https://github.com/ClickHouse/ClickHouse/pull/11388) ([filimonov](https://github.com/filimonov)).
- Add `port` function (to extract port from URL). [#11120](https://github.com/ClickHouse/ClickHouse/pull/11120) ([Azat Khuzhin](https://github.com/azat)).
- Now `dictGet*` functions accept table names. [#11050](https://github.com/ClickHouse/ClickHouse/pull/11050) ([Vitaly Baranov](https://github.com/vitlibar)).
- The `clickhouse-format` tool is now able to format multiple queries when the `-n` argument is used. [#10852](https://github.com/ClickHouse/ClickHouse/pull/10852) ([Darío](https://github.com/dgrr)).
- Possibility to configure proxy-resolver for DiskS3. [#10744](https://github.com/ClickHouse/ClickHouse/pull/10744) ([Pavel Kovalenko](https://github.com/Jokser)).
- Make `pointInPolygon` work with non-constant polygon. PointInPolygon now can take Array(Array(Tuple(..., ...))) as second argument, array of polygon and holes. [#10623](https://github.com/ClickHouse/ClickHouse/pull/10623) ([Alexey Ilyukhov](https://github.com/livace)) [#11421](https://github.com/ClickHouse/ClickHouse/pull/11421) ([Alexey Ilyukhov](https://github.com/livace)).
- Added `move_ttl_info` to `system.parts` in order to provide introspection of move TTL functionality. [#10591](https://github.com/ClickHouse/ClickHouse/pull/10591) ([Vladimir Chebotarev](https://github.com/excitoon)).
- Possibility to work with S3 through proxies. [#10576](https://github.com/ClickHouse/ClickHouse/pull/10576) ([Pavel Kovalenko](https://github.com/Jokser)).
- Add `NCHAR` and `NVARCHAR` synonims for data types. [#11025](https://github.com/ClickHouse/ClickHouse/pull/11025) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Resolved [#7224](https://github.com/ClickHouse/ClickHouse/issues/7224): added `FailedQuery`, `FailedSelectQuery` and `FailedInsertQuery` metrics to `system.events` table. [#11151](https://github.com/ClickHouse/ClickHouse/pull/11151) ([Nikita Orlov](https://github.com/naorlov)).
- Add more `jemalloc` statistics to `system.asynchronous_metrics`, and ensure that we see up-to-date values for them. [#11748](https://github.com/ClickHouse/ClickHouse/pull/11748) ([Alexander Kuzmenkov](https://github.com/akuzm)).
- Allow to specify default S3 credentials and custom auth headers. [#11134](https://github.com/ClickHouse/ClickHouse/pull/11134) ([Grigory Pervakov](https://github.com/GrigoryPervakov)).