### ClickHouse release v21.1.7.1-stable FIXME as compared to v21.1.6.13-stable

#### Bug Fix
* Backported in [#21261](https://github.com/ClickHouse/ClickHouse/issues/21261): fix default_replica_path and default_replica_name values are useless on Replicated(*)MergeTree engine when the engine needs specify other parameters. [#21060](https://github.com/ClickHouse/ClickHouse/pull/21060) ([mxzlxy](https://github.com/mxzlxy)).
* Backported in [#21155](https://github.com/ClickHouse/ClickHouse/issues/21155): fix bug related to cast tuple to map. Closes [#21029](https://github.com/ClickHouse/ClickHouse/issues/21029). [#21120](https://github.com/ClickHouse/ClickHouse/pull/21120) ([hexiaoting](https://github.com/hexiaoting)).
* Backported in [#21233](https://github.com/ClickHouse/ClickHouse/issues/21233): Now mutations allowed only for table engines that support them (MergeTree family, Memory, MaterializedView). Other engines will report a more clear error. Fixes [#21168](https://github.com/ClickHouse/ClickHouse/issues/21168). [#21183](https://github.com/ClickHouse/ClickHouse/pull/21183) ([alesapin](https://github.com/alesapin)).
* Backported in [#21428](https://github.com/ClickHouse/ClickHouse/issues/21428): Fix crash in `EXPLAIN` for query with `UNION`. Fixes [#20876](https://github.com/ClickHouse/ClickHouse/issues/20876), [#21170](https://github.com/ClickHouse/ClickHouse/issues/21170). [#21246](https://github.com/ClickHouse/ClickHouse/pull/21246) ([flynn](https://github.com/ucasfl)).
* Backported in [#21408](https://github.com/ClickHouse/ClickHouse/issues/21408): Fix redundant reconnects to ZooKeeper and the possibility of two active sessions for a single clickhouse server. Both problems introduced in [#14678](https://github.com/ClickHouse/ClickHouse/issues/14678). [#21264](https://github.com/ClickHouse/ClickHouse/pull/21264) ([alesapin](https://github.com/alesapin)).
* Backported in [#21549](https://github.com/ClickHouse/ClickHouse/issues/21549): Now `ALTER MODIFY COLUMN` queries will correctly affect changes in partition key, skip indices, TTLs, and so on. Fixes [#13675](https://github.com/ClickHouse/ClickHouse/issues/13675). [#21334](https://github.com/ClickHouse/ClickHouse/pull/21334) ([alesapin](https://github.com/alesapin)).
* Backported in [#21377](https://github.com/ClickHouse/ClickHouse/issues/21377): Fix error `Bad cast from type ... to DB::ColumnLowCardinality` while inserting into table with `LowCardinality` column from `Values` format. Fixes [#21140](https://github.com/ClickHouse/ClickHouse/issues/21140). [#21357](https://github.com/ClickHouse/ClickHouse/pull/21357) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).