2021 Changelog

#### Bug Fix[​](#bug-fix-1 "Direct link to Bug Fix")

- Fix cases, when reading compressed data from `carbon-clickhouse` fails with 'attempt to read after end of file'. Closes [#26149](https://github.com/ClickHouse/ClickHouse/issues/26149). [#28150](https://github.com/ClickHouse/ClickHouse/pull/28150) ([FArthur-cmd](https://github.com/FArthur-cmd)).
- Fix checking access grants when executing `GRANT WITH REPLACE` statement with `ON CLUSTER` clause. This PR improves fix [#27001](https://github.com/ClickHouse/ClickHouse/pull/27701). [#27983](https://github.com/ClickHouse/ClickHouse/pull/27983) ([Vitaly Baranov](https://github.com/vitlibar)).
- Allow selecting with `extremes = 1` from a column of the type `LowCardinality(UUID)`. [#27918](https://github.com/ClickHouse/ClickHouse/pull/27918) ([Vitaly Baranov](https://github.com/vitlibar)).
- Fix PostgreSQL-style cast (`::` operator) with negative numbers. [#27876](https://github.com/ClickHouse/ClickHouse/pull/27876) ([Anton Popov](https://github.com/CurtizJ)).
- After [#26864](https://github.com/ClickHouse/ClickHouse/pull/26864). Fix shutdown of `NamedSessionStorage`: session contexts stored in `NamedSessionStorage` are now destroyed before destroying the global context. [#27875](https://github.com/ClickHouse/ClickHouse/pull/27875) ([Vitaly Baranov](https://github.com/vitlibar)).
- Bugfix for `windowFunnel` "strict" mode. This fixes [#27469](https://github.com/ClickHouse/ClickHouse/issues/27469). [#27563](https://github.com/ClickHouse/ClickHouse/pull/27563) ([achimbab](https://github.com/achimbab)).
- Fix infinite loop while reading truncated `bzip2` archive. [#28543](https://github.com/ClickHouse/ClickHouse/pull/28543) ([Azat Khuzhin](https://github.com/azat)).
- Fix UUID overlap in `DROP TABLE` for internal DDL from `MaterializedMySQL`. MaterializedMySQL is an experimental feature. [#28533](https://github.com/ClickHouse/ClickHouse/pull/28533) ([Azat Khuzhin](https://github.com/azat)).
- Fix `There is no subcolumn` error, while select from tables, which have `Nested` columns and scalar columns with dot in name and the same prefix as `Nested` (e.g. `n.id UInt32, n.arr1 Array(UInt64), n.arr2 Array(UInt64)`). [#28531](https://github.com/ClickHouse/ClickHouse/pull/28531) ([Anton Popov](https://github.com/CurtizJ)).
- Fix bug which can lead to error `Existing table metadata in ZooKeeper differs in sorting key expression.` after ALTER of `ReplicatedVersionedCollapsingMergeTree`. Fixes [#28515](https://github.com/ClickHouse/ClickHouse/issues/28515). [#28528](https://github.com/ClickHouse/ClickHouse/pull/28528) ([alesapin](https://github.com/alesapin)).
- Fixed possible ZooKeeper watches leak (minor issue) on background processing of distributed DDL queue. Closes [#26036](https://github.com/ClickHouse/ClickHouse/issues/26036). [#28446](https://github.com/ClickHouse/ClickHouse/pull/28446) ([tavplubix](https://github.com/tavplubix)).
- Fix missing quoting of table names in `MaterializedPostgreSQL` engine. Closes [#28316](https://github.com/ClickHouse/ClickHouse/issues/28316). [#28433](https://github.com/ClickHouse/ClickHouse/pull/28433) ([Kseniia Sumarokova](https://github.com/kssenii)).
- Fix the wrong behaviour of non joined rows from nullable column. Close [#27691](https://github.com/ClickHouse/ClickHouse/issues/27691). [#28349](https://github.com/ClickHouse/ClickHouse/pull/28349) ([vdimir](https://github.com/vdimir)).
- Fix NOT-IN index optimization when not all key columns are used. This fixes [#28120](https://github.com/ClickHouse/ClickHouse/issues/28120). [#28315](https://github.com/ClickHouse/ClickHouse/pull/28315) ([Amos Bird](https://github.com/amosbird)).
- Fix intersecting parts due to new part had been replaced with an empty part. [#28310](https://github.com/ClickHouse/ClickHouse/pull/28310) ([Azat Khuzhin](https://github.com/azat)).
- Fix inconsistent result in queries with `ORDER BY` and `Merge` tables with enabled setting `optimize_read_in_order`. [#28266](https://github.com/ClickHouse/ClickHouse/pull/28266) ([Anton Popov](https://github.com/CurtizJ)).
- Fix possible read of uninitialized memory for queries with `Nullable(LowCardinality)` type and the setting `extremes` set to 1. Fixes [#28165](https://github.com/ClickHouse/ClickHouse/issues/28165). [#28205](https://github.com/ClickHouse/ClickHouse/pull/28205) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).
- Multiple small fixes for projections. See detailed description in the PR. [#28178](https://github.com/ClickHouse/ClickHouse/pull/28178) ([Amos Bird](https://github.com/amosbird)).
- Fix extremely rare segfaults on shutdown due to incorrect order of context/config reloader shutdown. [#28088](https://github.com/ClickHouse/ClickHouse/pull/28088) ([nvartolomei](https://github.com/nvartolomei)).
- Fix handling null value with type of `Nullable(String)` in function `JSONExtract`. This fixes [#27929](https://github.com/ClickHouse/ClickHouse/issues/27929) and [#27930](https://github.com/ClickHouse/ClickHouse/issues/27930). This was introduced in <https://github.com/ClickHouse/ClickHouse/pull/25452> . [#27939](https://github.com/ClickHouse/ClickHouse/pull/27939) ([Amos Bird](https://github.com/amosbird)).
- Multiple fixes for the new `clickhouse-keeper` tool. Fix a rare bug in `clickhouse-keeper` when the client can receive a watch response before request-response. [#28197](https://github.com/ClickHouse/ClickHouse/pull/28197) ([alesapin](https://github.com/alesapin)). Fix incorrect behavior in `clickhouse-keeper` when list watches (`getChildren`) triggered with `set` requests for children. [#28190](https://github.com/ClickHouse/ClickHouse/pull/28190) ([alesapin](https://github.com/alesapin)). Fix rare case when changes of `clickhouse-keeper` settings may lead to lost logs and server hung. [#28360](https://github.com/ClickHouse/ClickHouse/pull/28360) ([alesapin](https://github.com/alesapin)). Fix bug in `clickhouse-keeper` which can lead to endless logs when `rotate_logs_interval` decreased. [#28152](https://github.com/ClickHouse/ClickHouse/pull/28152) ([alesapin](https://github.com/alesapin)).

#### Build/Testing/Packaging Improvement[​](#buildtestingpackaging-improvement-2 "Direct link to Build/Testing/Packaging Improvement")

- Enable Thread Fuzzer in Stress Test. Thread Fuzzer is ClickHouse feature that allows to test more permutations of thread scheduling and discover more potential issues. This closes [#9813](https://github.com/ClickHouse/ClickHouse/issues/9813). This closes [#9814](https://github.com/ClickHouse/ClickHouse/issues/9814). This closes [#9515](https://github.com/ClickHouse/ClickHouse/issues/9515). This closes [#9516](https://github.com/ClickHouse/ClickHouse/issues/9516). [#27538](https://github.com/ClickHouse/ClickHouse/pull/27538) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Add new log level `test` for testing environments. It is even more verbose than the default `trace`. [#28559](https://github.com/ClickHouse/ClickHouse/pull/28559) ([alesapin](https://github.com/alesapin)).
- Print out git status information at CMake configure stage. [#28047](https://github.com/ClickHouse/ClickHouse/pull/28047) ([Braulio Valdivielso Martínez](https://github.com/BraulioVM)).
- Temporarily switched ubuntu apt repository to mirror ru.archive.ubuntu.com as the default one (archive.ubuntu.com) is not responding from our CI. [#28016](https://github.com/ClickHouse/ClickHouse/pull/28016) ([Ilya Yatsishin](https://github.com/qoega)).

### ClickHouse release v21.9, 2021-09-09[​](#clickhouse-release-v219-2021-09-09 "Direct link to ClickHouse release v21.9, 2021-09-09")

#### Backward Incompatible Change[​](#backward-incompatible-change-3 "Direct link to Backward Incompatible Change")