### ClickHouse release v21.5.7.9-stable FIXME as compared to v21.5.6.6-stable
#### Improvement
* Backported in [#24581](https://github.com/ClickHouse/ClickHouse/issues/24581): Disable min_bytes_to_use_mmap_io by default. [#23322](https://github.com/ClickHouse/ClickHouse/pull/23322) ([Azat Khuzhin](https://github.com/azat)).
* Backported in [#25222](https://github.com/ClickHouse/ClickHouse/issues/25222): Here will be listed all the bugs that I am gonna to fix in this PR. [#23518](https://github.com/ClickHouse/ClickHouse/pull/23518) ([Nikita Mikhaylov](https://github.com/nikitamikhaylov)).
* Backported in [#24793](https://github.com/ClickHouse/ClickHouse/issues/24793): Avoid hiding errors like `Limit for rows or bytes to read exceeded` for scalar subqueries. [#24545](https://github.com/ClickHouse/ClickHouse/pull/24545) ([nvartolomei](https://github.com/nvartolomei)).
#### Bug Fix
* Backported in [#24928](https://github.com/ClickHouse/ClickHouse/issues/24928): Fix implementation of connection pool of PostgreSQL engine. Closes [#23897](https://github.com/ClickHouse/ClickHouse/issues/23897). [#23909](https://github.com/ClickHouse/ClickHouse/pull/23909) ([Kseniia Sumarokova](https://github.com/kssenii)).
* Backported in [#24568](https://github.com/ClickHouse/ClickHouse/issues/24568): Use old modulo function version when used in partition key. Closes [#23508](https://github.com/ClickHouse/ClickHouse/issues/23508). [#24157](https://github.com/ClickHouse/ClickHouse/pull/24157) ([Kseniia Sumarokova](https://github.com/kssenii)).
* Backported in [#24726](https://github.com/ClickHouse/ClickHouse/issues/24726): In "multipart/form-data" message consider the CRLF preceding a boundary as part of it. Fixes [#23905](https://github.com/ClickHouse/ClickHouse/issues/23905). [#24399](https://github.com/ClickHouse/ClickHouse/pull/24399) ([Ivan](https://github.com/abyss7)).
* Backported in [#24824](https://github.com/ClickHouse/ClickHouse/issues/24824): - Fixed the deadlock that can happen during LDAP role (re)mapping, when LDAP group is mapped to a nonexistent local role. [#24431](https://github.com/ClickHouse/ClickHouse/pull/24431) ([Denis Glazachev](https://github.com/traceon)).
* Backported in [#24772](https://github.com/ClickHouse/ClickHouse/issues/24772): Fix bug which can lead to ZooKeeper client hung inside clickhouse-server. [#24721](https://github.com/ClickHouse/ClickHouse/pull/24721) ([alesapin](https://github.com/alesapin)).
* Backported in [#24935](https://github.com/ClickHouse/ClickHouse/issues/24935): - If ZooKeeper connection was lost and replica was cloned after restoring the connection, its replication queue might contain outdated entries. It's fixed. - Fixed crash when replication queue contains intersecting virtual parts. It may rarely happen if some data part was lost. Print error in log instead of terminating. [#24777](https://github.com/ClickHouse/ClickHouse/pull/24777) ([Alexander Tokmakov](https://github.com/tavplubix)).
* Backported in [#24854](https://github.com/ClickHouse/ClickHouse/issues/24854): Fix bug when exception `Mutation was killed` can be thrown to the client on mutation wait when mutation not loaded into memory yet. [#24809](https://github.com/ClickHouse/ClickHouse/pull/24809) ([alesapin](https://github.com/alesapin)).
* Backported in [#24986](https://github.com/ClickHouse/ClickHouse/issues/24986): Allow NULL values in postgresql protocol. Closes [#22622](https://github.com/ClickHouse/ClickHouse/issues/22622). [#24857](https://github.com/ClickHouse/ClickHouse/pull/24857) ([Kseniia Sumarokova](https://github.com/kssenii)).
* Backported in [#25481](https://github.com/ClickHouse/ClickHouse/issues/25481): Fix "Missing columns" exception when joining Distributed Materialized View. [#24870](https://github.com/ClickHouse/ClickHouse/pull/24870) ([Azat Khuzhin](https://github.com/azat)).
* Backported in [#24915](https://github.com/ClickHouse/ClickHouse/issues/24915): Fix extremely rare bug on low-memory servers which can lead to the inability to perform merges without restart. Possibly fixes [#24603](https://github.com/ClickHouse/ClickHouse/issues/24603). [#24872](https://github.com/ClickHouse/ClickHouse/pull/24872) ([alesapin](https://github.com/alesapin)).
* Backported in [#25183](https://github.com/ClickHouse/ClickHouse/issues/25183): Fixed bug with declaring S3 disk at root of bucket. Earlier, it reported an error: ``` [heather] 2021.05.10 02:11:11.932234 [ 72790 ] {2ff80b7b-ec53-41cb-ac35-19bb390e1759} <Error> executeQuery: Code: 36, e.displayText() = DB::Exception: Key name is empty in path style S3 URI: (http://172.17.0.2/bucket/) (version 21.6.1.1) (from 127.0.0.1:47994) (in query: SELECT policy_name FROM system.storage_policies), Stack trace (when copying this message, always include the lines below):. [#24898](https://github.com/ClickHouse/ClickHouse/pull/24898) ([Vladimir Chebotarev](https://github.com/excitoon)).
* Backported in [#24950](https://github.com/ClickHouse/ClickHouse/issues/24950): Fix possible heap-buffer-overflow in Arrow. [#24922](https://github.com/ClickHouse/ClickHouse/pull/24922) ([Kruglov Pavel](https://github.com/Avogar)).
* Backported in [#25024](https://github.com/ClickHouse/ClickHouse/issues/25024): Fix limit/offset settings for distributed queries (ignore on the remote nodes). [#24940](https://github.com/ClickHouse/ClickHouse/pull/24940) ([Azat Khuzhin](https://github.com/azat)).
* Backported in [#25048](https://github.com/ClickHouse/ClickHouse/issues/25048): Fix extremely rare error `Tagging already tagged part` in replication queue during concurrent `alter move/replace partition`. Possibly fixes [#22142](https://github.com/ClickHouse/ClickHouse/issues/22142). [#24961](https://github.com/ClickHouse/ClickHouse/pull/24961) ([alesapin](https://github.com/alesapin)).
* Backported in [#25365](https://github.com/ClickHouse/ClickHouse/issues/25365): Fix serialization of splitted nested messages in Protobuf format. This PR fixes [#24647](https://github.com/ClickHouse/ClickHouse/issues/24647). [#25000](https://github.com/ClickHouse/ClickHouse/pull/25000) ([Vitaly Baranov](https://github.com/vitlibar)).
* Backported in [#25101](https://github.com/ClickHouse/ClickHouse/issues/25101): Distinguish KILL MUTATION for different tables (fixes unexpected `Cancelled mutating parts` error). [#25025](https://github.com/ClickHouse/ClickHouse/pull/25025) ([Azat Khuzhin](https://github.com/azat)).
* Backported in [#25558](https://github.com/ClickHouse/ClickHouse/issues/25558): Fix bug which allows creating tables with columns referencing themselves like `a UInt32 ALIAS a + 1` or `b UInt32 MATERIALIZED b`. Fixes [#24910](https://github.com/ClickHouse/ClickHouse/issues/24910), [#24292](https://github.com/ClickHouse/ClickHouse/issues/24292). [#25059](https://github.com/ClickHouse/ClickHouse/pull/25059) ([alesapin](https://github.com/alesapin)).
* Backported in [#25104](https://github.com/ClickHouse/ClickHouse/issues/25104): Fix bug with constant maps in mapContains that lead to error `empty column was returned by function mapContains`. Closes [#25077](https://github.com/ClickHouse/ClickHouse/issues/25077). [#25080](https://github.com/ClickHouse/ClickHouse/pull/25080) ([Kruglov Pavel](https://github.com/Avogar)).
* Backported in [#25141](https://github.com/ClickHouse/ClickHouse/issues/25141): Fix crash in query with cross join and `joined_subquery_requires_alias = 0`. Fixes [#24011](https://github.com/ClickHouse/ClickHouse/issues/24011). [#25082](https://github.com/ClickHouse/ClickHouse/pull/25082) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).
* Backported in [#25214](https://github.com/ClickHouse/ClickHouse/issues/25214): Fixed an error which occurred while inserting a subset of columns using CSVWithNames format. Fixes [#25129](https://github.com/ClickHouse/ClickHouse/issues/25129). [#25169](https://github.com/ClickHouse/ClickHouse/pull/25169) ([Nikita Mikhaylov](https://github.com/nikitamikhaylov)).
* Backported in [#25353](https://github.com/ClickHouse/ClickHouse/issues/25353): Fix TOCTOU error in installation script. [#25277](https://github.com/ClickHouse/ClickHouse/pull/25277) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Backported in [#25471](https://github.com/ClickHouse/ClickHouse/issues/25471): Fix joinGetOrNull with not-nullable columns. This fixes [#24261](https://github.com/ClickHouse/ClickHouse/issues/24261). [#25288](https://github.com/ClickHouse/ClickHouse/pull/25288) ([Amos Bird](https://github.com/amosbird)).
* Backported in [#25357](https://github.com/ClickHouse/ClickHouse/issues/25357): Fix Logical Error Cannot sum Array/Tuple in min/maxMap. [#25298](https://github.com/ClickHouse/ClickHouse/pull/25298) ([Kruglov Pavel](https://github.com/Avogar)).
* Backported in [#25438](https://github.com/ClickHouse/ClickHouse/issues/25438): Support `SimpleAggregateFunction(LowCardinality)` for `SummingMergeTree`. Fixes [#25134](https://github.com/ClickHouse/ClickHouse/issues/25134). [#25300](https://github.com/ClickHouse/ClickHouse/pull/25300) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).
* Backported in [#25362](https://github.com/ClickHouse/ClickHouse/issues/25362): On ZooKeeper connection loss `ReplicatedMergeTree` table might wait for background operations to complete before trying to reconnect. It's fixed, now background operations are stopped forcefully. [#25306](https://github.com/ClickHouse/ClickHouse/pull/25306) ([Alexander Tokmakov](https://github.com/tavplubix)).
* Backported in [#25386](https://github.com/ClickHouse/ClickHouse/issues/25386): Fix the possibility of non-deterministic behaviour of the `quantileDeterministic` function and similar. This closes [#20480](https://github.com/ClickHouse/ClickHouse/issues/20480). [#25313](https://github.com/ClickHouse/ClickHouse/pull/25313) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Backported in [#25456](https://github.com/ClickHouse/ClickHouse/issues/25456): Fix lost `WHERE` condition in expression-push-down optimization of query plan (setting `query_plan_filter_push_down = 1` by default). Fixes [#25368](https://github.com/ClickHouse/ClickHouse/issues/25368). [#25370](https://github.com/ClickHouse/ClickHouse/pull/25370) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).
* Backported in [#25408](https://github.com/ClickHouse/ClickHouse/issues/25408): Fix `REPLACE` column transformer when used in DDL by correctly quoting the formated query. This fixes [#23925](https://github.com/ClickHouse/ClickHouse/issues/23925). [#25391](https://github.com/ClickHouse/ClickHouse/pull/25391) ([Amos Bird](https://github.com/amosbird)).
* Backported in [#25504](https://github.com/ClickHouse/ClickHouse/issues/25504): Fix segfault when sharding_key is absent in task config for copier. [#25419](https://github.com/ClickHouse/ClickHouse/pull/25419) ([Nikita Mikhaylov](https://github.com/nikitamikhaylov)).
#### NO CL ENTRY
* NO CL ENTRY: 'Revert "Backport [#24721](https://github.com/ClickHouse/ClickHouse/issues/24721) to 21.5: Remove endless `wait` from ZooKeeper client"'. [#24798](https://github.com/ClickHouse/ClickHouse/pull/24798) ([alesapin](https://github.com/alesapin)).
