2020 Changelog

#### New Feature[​](#new-feature-12 "Direct link to New Feature")

- Add `deduplicate_blocks_in_dependent_materialized_views` option to control the behaviour of idempotent inserts into tables with materialized views. This new feature was added to the bugfix release by a special request from Altinity.
  [#9070](https://github.com/ClickHouse/ClickHouse/pull/9070) [(urykhy)](https://github.com/urykhy)

### ClickHouse release v20.1.2.4, 2020-01-22[​](#clickhouse-release-v20124-2020-01-22 "Direct link to ClickHouse release v20.1.2.4, 2020-01-22")

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

- Make the setting `merge_tree_uniform_read_distribution` obsolete. The server still recognizes this setting but it has no effect. [#8308](https://github.com/ClickHouse/ClickHouse/pull/8308) ([alexey-milovidov](https://github.com/alexey-milovidov))
- Changed return type of the function `greatCircleDistance` to `Float32` because now the result of calculation is `Float32`. [#7993](https://github.com/ClickHouse/ClickHouse/pull/7993) ([alexey-milovidov](https://github.com/alexey-milovidov))
- Now it's expected that query parameters are represented in "escaped" format. For example, to pass string `a<tab>b` you have to write `a\tb` or `a\<tab>b` and respectively, `a%5Ctb` or `a%5C%09b` in URL. This is needed to add the possibility to pass NULL as `\N`. This fixes [#7488](https://github.com/ClickHouse/ClickHouse/issues/7488). [#8517](https://github.com/ClickHouse/ClickHouse/pull/8517) ([alexey-milovidov](https://github.com/alexey-milovidov))
- Enable `use_minimalistic_part_header_in_zookeeper` setting for `ReplicatedMergeTree` by default. This will significantly reduce amount of data stored in ZooKeeper. This setting is supported since version 19.1 and we already use it in production in multiple services without any issues for more than half a year. Disable this setting if you have a chance to downgrade to versions older than 19.1. [#6850](https://github.com/ClickHouse/ClickHouse/pull/6850) ([alexey-milovidov](https://github.com/alexey-milovidov))
- Data skipping indices are production ready and enabled by default. The settings `allow_experimental_data_skipping_indices`, `allow_experimental_cross_to_join_conversion` and `allow_experimental_multiple_joins_emulation` are now obsolete and do nothing. [#7974](https://github.com/ClickHouse/ClickHouse/pull/7974) ([alexey-milovidov](https://github.com/alexey-milovidov))
- Add new `ANY JOIN` logic for `StorageJoin` consistent with `JOIN` operation. To upgrade without changes in behaviour you need add `SETTINGS any_join_distinct_right_table_keys = 1` to Engine Join tables metadata or recreate these tables after upgrade. [#8400](https://github.com/ClickHouse/ClickHouse/pull/8400) ([Artem Zuikov](https://github.com/4ertus2))
- Require server to be restarted to apply the changes in logging configuration. This is a temporary workaround to avoid the bug where the server logs to a deleted log file (see [#8696](https://github.com/ClickHouse/ClickHouse/issues/8696)). [#8707](https://github.com/ClickHouse/ClickHouse/pull/8707) ([Alexander Kuzmenkov](https://github.com/akuzm))

#### New Feature[​](#new-feature-13 "Direct link to New Feature")