2021 Changelog

### ClickHouse release v21.1.2.15-stable 2021-01-18[​](#clickhouse-release-v211215-stable-2021-01-18 "Direct link to ClickHouse release v21.1.2.15-stable 2021-01-18")

#### Backward Incompatible Change[​](#backward-incompatible-change-10 "Direct link to Backward Incompatible Change")

- The setting `input_format_null_as_default` is enabled by default. [#17525](https://github.com/ClickHouse/ClickHouse/pull/17525) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Check settings constraints for profile settings from config. Server will fail to start if users.xml contain settings that do not meet corresponding constraints. [#18486](https://github.com/ClickHouse/ClickHouse/pull/18486) ([tavplubix](https://github.com/tavplubix)).
- Restrict `ALTER MODIFY SETTING` from changing storage settings that affects data parts (`write_final_mark` and `enable_mixed_granularity_parts`). [#18306](https://github.com/ClickHouse/ClickHouse/pull/18306) ([Amos Bird](https://github.com/amosbird)).
- Set `insert_quorum_parallel` to 1 by default. It is significantly more convenient to use than "sequential" quorum inserts. But if you rely to sequential consistency, you should set the setting back to zero. [#17567](https://github.com/ClickHouse/ClickHouse/pull/17567) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Remove `sumburConsistentHash` function. This closes [#18120](https://github.com/ClickHouse/ClickHouse/issues/18120). [#18656](https://github.com/ClickHouse/ClickHouse/pull/18656) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Removed aggregate functions `timeSeriesGroupSum`, `timeSeriesGroupRateSum` because a friend of mine said they never worked. This fixes [#16869](https://github.com/ClickHouse/ClickHouse/issues/16869). If you have luck using these functions, write a email to [[email protected]](/cdn-cgi/l/email-protection#0e686b6b6a6c6f6d654e6d62676d6566617b7d6b206d6163). [#17423](https://github.com/ClickHouse/ClickHouse/pull/17423) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Prohibit toUnixTimestamp(Date()) (before it just returns UInt16 representation of Date). [#17376](https://github.com/ClickHouse/ClickHouse/pull/17376) ([Azat Khuzhin](https://github.com/azat)).
- Allow using extended integer types (`Int128`, `Int256`, `UInt256`) in `avg` and `avgWeighted` functions. Also allow using different types (integer, decimal, floating point) for value and for weight in `avgWeighted` function. This is a backward-incompatible change: now the `avg` and `avgWeighted` functions always return `Float64` (as documented). Before this change the return type for `Decimal` arguments was also `Decimal`. [#15419](https://github.com/ClickHouse/ClickHouse/pull/15419) ([Mike](https://github.com/myrrc)).
- Expression `toUUID(N)` no longer works. Replace with `toUUID('00000000-0000-0000-0000-000000000000')`. This change is motivated by non-obvious results of `toUUID(N)` where N is non zero.
- SSL Certificates with incorrect "key usage" are rejected. In previous versions they are used to work. See [#19262](https://github.com/ClickHouse/ClickHouse/issues/19262).
- `incl` references to substitutions file (`/etc/metrika.xml`) were removed from the default config (`<remote_servers>`, `<zookeeper>`, `<macros>`, `<compression>`, `<networks>`). If you were using substitutions file and were relying on those implicit references, you should put them back manually and explicitly by adding corresponding sections with `incl="..."` attributes before the update. See [#18740](https://github.com/ClickHouse/ClickHouse/pull/18740) ([alexey-milovidov](https://github.com/alexey-milovidov)).

#### New Feature[​](#new-feature-10 "Direct link to New Feature")