### ClickHouse release v21.4.4.30-stable FIXME as compared to v21.4.3.21-stable
#### Backward Incompatible Change
* Backported in [#23145](https://github.com/ClickHouse/ClickHouse/issues/23145): Now replicas that are processing the `ALTER TABLE ATTACH PART[ITION]` command search in their `detached/` folders before fetching the data from other replicas. As an implementation detail, a new command `ATTACH_PART` is introduced in the replicated log. Parts are searched and compared by their checksums. [#18978](https://github.com/ClickHouse/ClickHouse/pull/18978) ([Mike Kot](https://github.com/myrrc)).
#### New Feature
* Backported in [#23147](https://github.com/ClickHouse/ClickHouse/issues/23147): Improved performance of `dictGetHierarchy`, `dictIsIn` functions. 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)).
* Backported in [#23146](https://github.com/ClickHouse/ClickHouse/issues/23146): 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)).
#### Improvement
* Backported in [#23148](https://github.com/ClickHouse/ClickHouse/issues/23148): Add aliases `simpleJSONExtract/simpleJSONHas` to `visitParam/visitParamExtract{UInt, Int, Bool, Float, Raw, String}`. Fixes [#21383](https://github.com/ClickHouse/ClickHouse/issues/21383). [#21519](https://github.com/ClickHouse/ClickHouse/pull/21519) ([fastio](https://github.com/fastio)).
* Backported in [#23016](https://github.com/ClickHouse/ClickHouse/issues/23016): Set `background_fetches_pool_size` to 8 that is better for production usage with frequent small insertions or slow ZooKeeper cluster. [#22945](https://github.com/ClickHouse/ClickHouse/pull/22945) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Backported in [#23079](https://github.com/ClickHouse/ClickHouse/issues/23079): Raised the threshold on max number of matches in result of the function `extractAllGroupsHorizontal`. [#23036](https://github.com/ClickHouse/ClickHouse/pull/23036) ([Vasily Nemkov](https://github.com/Enmk)).
#### Bug Fix
* Backported in [#23158](https://github.com/ClickHouse/ClickHouse/issues/23158): Fixed a bug with unlimited wait for auxiliary AWS requests. [#22594](https://github.com/ClickHouse/ClickHouse/pull/22594) ([Vladimir Chebotarev](https://github.com/excitoon)).
* Backported in [#23018](https://github.com/ClickHouse/ClickHouse/issues/23018): fixed `formatDateTime()` on `DateTime64` and "%C" format specifier fixed `toDateTime64()` for large values and non-zero scale. ... [#22937](https://github.com/ClickHouse/ClickHouse/pull/22937) ([Vasily Nemkov](https://github.com/Enmk)).
* Backported in [#23031](https://github.com/ClickHouse/ClickHouse/issues/23031): Fix error `Cannot find column in ActionsDAG result` which may happen if subquery uses `untuple`. Fixes [#22290](https://github.com/ClickHouse/ClickHouse/issues/22290). [#22991](https://github.com/ClickHouse/ClickHouse/pull/22991) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).
* Backported in [#23074](https://github.com/ClickHouse/ClickHouse/issues/23074): Remove non-essential details from suggestions in clickhouse-client. This closes [#22158](https://github.com/ClickHouse/ClickHouse/issues/22158). [#23040](https://github.com/ClickHouse/ClickHouse/pull/23040) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Backported in [#23097](https://github.com/ClickHouse/ClickHouse/issues/23097): Fixed `Table .inner_id... doesn't exist` error when selecting from Materialized View after detaching it from Atomic database and attaching back. [#23047](https://github.com/ClickHouse/ClickHouse/pull/23047) ([Alexander Tokmakov](https://github.com/tavplubix)).
* Backported in [#23173](https://github.com/ClickHouse/ClickHouse/issues/23173): Some values were formatted with alignment in center in table cells in `Markdown` format. Not anymore. [#23096](https://github.com/ClickHouse/ClickHouse/pull/23096) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
#### Build/Testing/Packaging Improvement
* Backported in [#23149](https://github.com/ClickHouse/ClickHouse/issues/23149): Enable the bundled openldap on ppc64le ... [#22487](https://github.com/ClickHouse/ClickHouse/pull/22487) ([Kfir Itzhak](https://github.com/mastertheknife)).
