2020 Changelog

### ClickHouse release v20.9.4.76-stable (2020-10-29)[​](#clickhouse-release-v209476-stable-2020-10-29 "Direct link to ClickHouse release v20.9.4.76-stable (2020-10-29)")

#### Bug Fix[​](#bug-fix-13 "Direct link to Bug Fix")

- Fix double free in case of exception in function `dictGet`. It could have happened if dictionary was loaded with error. [#16429](https://github.com/ClickHouse/ClickHouse/pull/16429) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).
- Fix group by with totals/rollup/cube modifers and min/max functions over group by keys. Fixes [#16393](https://github.com/ClickHouse/ClickHouse/issues/16393). [#16397](https://github.com/ClickHouse/ClickHouse/pull/16397) ([Anton Popov](https://github.com/CurtizJ)).
- Fix async Distributed INSERT w/ prefer\_localhost\_replica=0 and internal\_replication. [#16358](https://github.com/ClickHouse/ClickHouse/pull/16358) ([Azat Khuzhin](https://github.com/azat)).
- Fix a very wrong code in TwoLevelStringHashTable implementation, which might lead to memory leak. I'm suprised how this bug can lurk for so long.... [#16264](https://github.com/ClickHouse/ClickHouse/pull/16264) ([Amos Bird](https://github.com/amosbird)).
- Fix the case when memory can be overallocated regardless to the limit. This closes [#14560](https://github.com/ClickHouse/ClickHouse/issues/14560). [#16206](https://github.com/ClickHouse/ClickHouse/pull/16206) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Fix `ALTER MODIFY ... ORDER BY` query hang for `ReplicatedVersionedCollapsingMergeTree`. This fixes [#15980](https://github.com/ClickHouse/ClickHouse/issues/15980). [#16011](https://github.com/ClickHouse/ClickHouse/pull/16011) ([alesapin](https://github.com/alesapin)).
- Fix collate name & charset name parser and support `length = 0` for string type. [#16008](https://github.com/ClickHouse/ClickHouse/pull/16008) ([Winter Zhang](https://github.com/zhang2014)).
- Allow to use direct layout for dictionaries with complex keys. [#16007](https://github.com/ClickHouse/ClickHouse/pull/16007) ([Anton Popov](https://github.com/CurtizJ)).
- Prevent replica hang for 5-10 mins when replication error happens after a period of inactivity. [#15987](https://github.com/ClickHouse/ClickHouse/pull/15987) ([filimonov](https://github.com/filimonov)).
- Fix rare segfaults when inserting into or selecting from MaterializedView and concurrently dropping target table (for Atomic database engine). [#15984](https://github.com/ClickHouse/ClickHouse/pull/15984) ([tavplubix](https://github.com/tavplubix)).
- Fix ambiguity in parsing of settings profiles: `CREATE USER ... SETTINGS profile readonly` is now considered as using a profile named `readonly`, not a setting named `profile` with the readonly constraint. This fixes [#15628](https://github.com/ClickHouse/ClickHouse/issues/15628). [#15982](https://github.com/ClickHouse/ClickHouse/pull/15982) ([Vitaly Baranov](https://github.com/vitlibar)).
- Fix a crash when database creation fails. [#15954](https://github.com/ClickHouse/ClickHouse/pull/15954) ([Winter Zhang](https://github.com/zhang2014)).
- Fixed `DROP TABLE IF EXISTS` failure with `Table ... does not exist` error when table is concurrently renamed (for Atomic database engine). Fixed rare deadlock when concurrently executing some DDL queries with multiple tables (like `DROP DATABASE` and `RENAME TABLE`) Fixed `DROP/DETACH DATABASE` failure with `Table ... does not exist` when concurrently executing `DROP/DETACH TABLE`. [#15934](https://github.com/ClickHouse/ClickHouse/pull/15934) ([tavplubix](https://github.com/tavplubix)).
- Fix incorrect empty result for query from `Distributed` table if query has `WHERE`, `PREWHERE` and `GLOBAL IN`. Fixes [#15792](https://github.com/ClickHouse/ClickHouse/issues/15792). [#15933](https://github.com/ClickHouse/ClickHouse/pull/15933) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).
- Fix possible deadlocks in RBAC. [#15875](https://github.com/ClickHouse/ClickHouse/pull/15875) ([Vitaly Baranov](https://github.com/vitlibar)).
- Fix exception `Block structure mismatch` in `SELECT ... ORDER BY DESC` queries which were executed after `ALTER MODIFY COLUMN` query. Fixes [#15800](https://github.com/ClickHouse/ClickHouse/issues/15800). [#15852](https://github.com/ClickHouse/ClickHouse/pull/15852) ([alesapin](https://github.com/alesapin)).
- Fix `select count()` inaccuracy for MaterializeMySQL. [#15767](https://github.com/ClickHouse/ClickHouse/pull/15767) ([tavplubix](https://github.com/tavplubix)).
- Fix some cases of queries, in which only virtual columns are selected. Previously `Not found column _nothing in block` exception may be thrown. Fixes [#12298](https://github.com/ClickHouse/ClickHouse/issues/12298). [#15756](https://github.com/ClickHouse/ClickHouse/pull/15756) ([Anton Popov](https://github.com/CurtizJ)).
- Fixed too low default value of `max_replicated_logs_to_keep` setting, which might cause replicas to become lost too often. Improve lost replica recovery process by choosing the most up-to-date replica to clone. Also do not remove old parts from lost replica, detach them instead. [#15701](https://github.com/ClickHouse/ClickHouse/pull/15701) ([tavplubix](https://github.com/tavplubix)).
- Fix error `Cannot add simple transform to empty Pipe` which happened while reading from `Buffer` table which has different structure than destination table. It was possible if destination table returned empty result for query. Fixes [#15529](https://github.com/ClickHouse/ClickHouse/issues/15529). [#15662](https://github.com/ClickHouse/ClickHouse/pull/15662) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).
- Fixed bug with globs in S3 table function, region from URL was not applied to S3 client configuration. [#15646](https://github.com/ClickHouse/ClickHouse/pull/15646) ([Vladimir Chebotarev](https://github.com/excitoon)).
- Decrement the `ReadonlyReplica` metric when detaching read-only tables. This fixes [#15598](https://github.com/ClickHouse/ClickHouse/issues/15598). [#15592](https://github.com/ClickHouse/ClickHouse/pull/15592) ([sundyli](https://github.com/sundy-li)).
- Throw an error when a single parameter is passed to ReplicatedMergeTree instead of ignoring it. [#15516](https://github.com/ClickHouse/ClickHouse/pull/15516) ([nvartolomei](https://github.com/nvartolomei)).

#### Improvement[​](#improvement-6 "Direct link to Improvement")

- Now it's allowed to execute `ALTER ... ON CLUSTER` queries regardless of the `<internal_replication>` setting in cluster config. [#16075](https://github.com/ClickHouse/ClickHouse/pull/16075) ([alesapin](https://github.com/alesapin)).
- Unfold `{database}`, `{table}` and `{uuid}` macros in `ReplicatedMergeTree` arguments on table creation. [#16160](https://github.com/ClickHouse/ClickHouse/pull/16160) ([tavplubix](https://github.com/tavplubix)).

### ClickHouse release v20.9.3.45-stable (2020-10-09)[​](#clickhouse-release-v209345-stable-2020-10-09 "Direct link to ClickHouse release v20.9.3.45-stable (2020-10-09)")

#### Bug Fix[​](#bug-fix-14 "Direct link to Bug Fix")