### ClickHouse release v21.8.6.15-lts FIXME as compared to v21.8.5.7-lts
#### Improvement
* Backported in [#28899](https://github.com/ClickHouse/ClickHouse/issues/28899): Use real tmp file instead of predefined "rows_sources" for vertical merges. This avoids generating garbage directories in tmp disks. [#28299](https://github.com/ClickHouse/ClickHouse/pull/28299) ([Amos Bird](https://github.com/amosbird)).
* Backported in [#28642](https://github.com/ClickHouse/ClickHouse/issues/28642): Fix strange sessions expiration logic in Keeper. Probably it should help in CI: https://clickhouse-test-reports.s3.yandex.net/0/6bd9b82141c98dcd7796fd9d08326831095ba519/stress_test_(debug).html#fail1. [#28519](https://github.com/ClickHouse/ClickHouse/pull/28519) ([alesapin](https://github.com/alesapin)).
* Backported in [#28718](https://github.com/ClickHouse/ClickHouse/issues/28718): To be added. Closes [#28529](https://github.com/ClickHouse/ClickHouse/issues/28529). [#28614](https://github.com/ClickHouse/ClickHouse/pull/28614) ([Kseniia Sumarokova](https://github.com/kssenii)).
#### Bug Fix
* Backported in [#27923](https://github.com/ClickHouse/ClickHouse/issues/27923): Fix PostgreSQL-style cast (`::` operator) with negative numbers. [#27876](https://github.com/ClickHouse/ClickHouse/pull/27876) ([Anton Popov](https://github.com/CurtizJ)).
* Backported in [#28753](https://github.com/ClickHouse/ClickHouse/issues/28753): Fix transformation of disjunctions chain to `IN` (controlled by settings `optimize_min_equality_disjunction_chain_length`) in distributed queries with settings `legacy_column_name_of_tuple_literal = 0`. [#28658](https://github.com/ClickHouse/ClickHouse/pull/28658) ([Anton Popov](https://github.com/CurtizJ)).
* Backported in [#28644](https://github.com/ClickHouse/ClickHouse/issues/28644): 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)).
* Backported in [#28508](https://github.com/ClickHouse/ClickHouse/issues/28508): Fix lack of quotes for 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)).
* Backported in [#28510](https://github.com/ClickHouse/ClickHouse/issues/28510): Fixed possible ZooKeeper watches leak on background processing of distributed DDL queue. Closes [#26036](https://github.com/ClickHouse/ClickHouse/issues/26036). [#28446](https://github.com/ClickHouse/ClickHouse/pull/28446) ([Alexander Tokmakov](https://github.com/tavplubix)).
* Backported in [#28573](https://github.com/ClickHouse/ClickHouse/issues/28573): 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)).
* Backported in [#28597](https://github.com/ClickHouse/ClickHouse/issues/28597): 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)).
* Backported in [#28714](https://github.com/ClickHouse/ClickHouse/issues/28714): Add Settings.Names, Settings.Values aliases for system.processes table. [#28685](https://github.com/ClickHouse/ClickHouse/pull/28685) ([Vitaly Orlov](https://github.com/orloffv)).
* Backported in [#28741](https://github.com/ClickHouse/ClickHouse/issues/28741): Fix the coredump in the creation of distributed tables, when the parameters passed in are wrong. [#28686](https://github.com/ClickHouse/ClickHouse/pull/28686) ([Zhiyong Wang](https://github.com/ljcui)).
* Backported in [#28791](https://github.com/ClickHouse/ClickHouse/issues/28791): Fix benign race condition in ReplicatedMergeTreeQueue. Shouldn't be visible for user, but can lead to subtle bugs. [#28734](https://github.com/ClickHouse/ClickHouse/pull/28734) ([alesapin](https://github.com/alesapin)).
* Backported in [#28994](https://github.com/ClickHouse/ClickHouse/issues/28994): Fixed a race condition between `DROP PART` and `REPLACE/MOVE PARTITION` that might cause replicas to diverge in rare cases. [#28864](https://github.com/ClickHouse/ClickHouse/pull/28864) ([Alexander Tokmakov](https://github.com/tavplubix)).
* Backported in [#28948](https://github.com/ClickHouse/ClickHouse/issues/28948): Fix reading of subcolumns from compact parts. [#28873](https://github.com/ClickHouse/ClickHouse/pull/28873) ([Anton Popov](https://github.com/CurtizJ)).
* Backported in [#28930](https://github.com/ClickHouse/ClickHouse/issues/28930): Fix higher-order array functions (`SIGSEGV` for `arrayCompact`/`ILLEGAL_COLUMN` for `arrayDifference`/`arrayCumSumNonNegative`) with consts. [#28904](https://github.com/ClickHouse/ClickHouse/pull/28904) ([Azat Khuzhin](https://github.com/azat)).
* Add more checks for LC in native protocol. [#27827](https://github.com/ClickHouse/ClickHouse/pull/27827) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).
* Function dictGet default implementation for nulls [#28530](https://github.com/ClickHouse/ClickHouse/pull/28530) ([Maksim Kita](https://github.com/kitaisreal)).
* Fix usage of nested columns with non-array columns with the same prefix [2] [#28762](https://github.com/ClickHouse/ClickHouse/pull/28762) ([Anton Popov](https://github.com/CurtizJ)).
* Lower compiled_expression_cache_size to 128MB [#28816](https://github.com/ClickHouse/ClickHouse/pull/28816) ([Maksim Kita](https://github.com/kitaisreal)).
* Fix some images in release PRs [#29059](https://github.com/ClickHouse/ClickHouse/pull/29059) ([alesapin](https://github.com/alesapin)).
