### ClickHouse release v21.3.16.5-lts FIXME as compared to v21.3.15.4-stable

#### Bug Fix
* Backported in [#26940](https://github.com/ClickHouse/ClickHouse/issues/26940): Do not remove data on ReplicatedMergeTree table shutdown to avoid creating data to metadata inconsistency. [#26716](https://github.com/ClickHouse/ClickHouse/pull/26716) ([nvartolomei](https://github.com/nvartolomei)).
* Backported in [#26983](https://github.com/ClickHouse/ClickHouse/issues/26983): Aggregate function parameters might be lost when applying some combinators causing exceptions like `Conversion from AggregateFunction(topKArray, Array(String)) to AggregateFunction(topKArray(10), Array(String)) is not supported`. It's fixed. Fixes [#26196](https://github.com/ClickHouse/ClickHouse/issues/26196) and [#26433](https://github.com/ClickHouse/ClickHouse/issues/26433). [#26814](https://github.com/ClickHouse/ClickHouse/pull/26814) ([Alexander Tokmakov](https://github.com/tavplubix)).
* Backported in [#26998](https://github.com/ClickHouse/ClickHouse/issues/26998): Fix reading of custom TLDs (stops processing with lower buffer or bigger file). [#26948](https://github.com/ClickHouse/ClickHouse/pull/26948) ([Azat Khuzhin](https://github.com/azat)).
* Backported in [#27088](https://github.com/ClickHouse/ClickHouse/issues/27088): Now partition ID in queries like `ALTER TABLE ... PARTITION ID xxx` validates for correctness. Fixes [#25718](https://github.com/ClickHouse/ClickHouse/issues/25718). [#26963](https://github.com/ClickHouse/ClickHouse/pull/26963) ([alesapin](https://github.com/alesapin)).
* Backported in [#27049](https://github.com/ClickHouse/ClickHouse/issues/27049): [RFC] Fix possible mutation stack due to race with DROP_RANGE. [#27002](https://github.com/ClickHouse/ClickHouse/pull/27002) ([Azat Khuzhin](https://github.com/azat)).
* Backported in [#27158](https://github.com/ClickHouse/ClickHouse/issues/27158): Fix synchronization in GRPCServer This PR fixes [#27024](https://github.com/ClickHouse/ClickHouse/issues/27024). [#27064](https://github.com/ClickHouse/ClickHouse/pull/27064) ([Vitaly Baranov](https://github.com/vitlibar)).
* Backported in [#27368](https://github.com/ClickHouse/ClickHouse/issues/27368): - Fix uninitialized memory in functions `multiSearch*` with empty array, close [#27169](https://github.com/ClickHouse/ClickHouse/issues/27169). [#27181](https://github.com/ClickHouse/ClickHouse/pull/27181) ([Vladimir C](https://github.com/vdimir)).
* Backported in [#27264](https://github.com/ClickHouse/ClickHouse/issues/27264): In rare cases `system.detached_parts` table might contain incorrect information for some parts, it's fixed. Fixes [#27114](https://github.com/ClickHouse/ClickHouse/issues/27114). [#27183](https://github.com/ClickHouse/ClickHouse/pull/27183) ([Alexander Tokmakov](https://github.com/tavplubix)).
* Backported in [#27413](https://github.com/ClickHouse/ClickHouse/issues/27413): Fixed incorrect validation of partition id for MergeTree tables that created with old syntax. [#27328](https://github.com/ClickHouse/ClickHouse/pull/27328) ([Alexander Tokmakov](https://github.com/tavplubix)).
* Backported in [#27645](https://github.com/ClickHouse/ClickHouse/issues/27645): Fix incorrect result for query with row-level security, prewhere and LowCardinality filter. Fixes [#27179](https://github.com/ClickHouse/ClickHouse/issues/27179). [#27329](https://github.com/ClickHouse/ClickHouse/pull/27329) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).
* Backported in [#27473](https://github.com/ClickHouse/ClickHouse/issues/27473): fix metric BackgroundMessageBrokerSchedulePoolTask, maybe mistyped。. [#27452](https://github.com/ClickHouse/ClickHouse/pull/27452) ([Ben](https://github.com/benbiti)).
* Backported in [#27864](https://github.com/ClickHouse/ClickHouse/issues/27864): Prevent crashes for some formats when NULL (tombstone) message was coming from Kafka. Closes [#19255](https://github.com/ClickHouse/ClickHouse/issues/19255). [#27794](https://github.com/ClickHouse/ClickHouse/pull/27794) ([filimonov](https://github.com/filimonov)).
* Backported in [#28207](https://github.com/ClickHouse/ClickHouse/issues/28207): Fix cases, when read buffer 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) ([Filatenkov Artur](https://github.com/FArthur-cmd)).

#### Build/Testing/Packaging Improvement
* Backported in [#28075](https://github.com/ClickHouse/ClickHouse/issues/28075): Temporarily switched ubuntu apt repository to mirror ru.archive.ubuntu.com as 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)).

#### Bug Fix (user-visible misbehaviour in official stable or prestable release)

* Backported in [#28181](https://github.com/ClickHouse/ClickHouse/issues/28181): Fixed possible excessive number of conditions moved from `WHERE` to `PREWHERE` (optimization controlled by settings `optimize_move_to_prewhere`). [#28139](https://github.com/ClickHouse/ClickHouse/pull/28139) ([lthaooo](https://github.com/lthaooo)).
* Backported in [#28293](https://github.com/ClickHouse/ClickHouse/issues/28293): 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)).