2020 Changelog

## ClickHouse release 20.7[​](#clickhouse-release-207 "Direct link to ClickHouse release 20.7")

### ClickHouse release v20.7.2.30-stable, 2020-08-31[​](#clickhouse-release-v207230-stable-2020-08-31 "Direct link to ClickHouse release v20.7.2.30-stable, 2020-08-31")

#### Backward Incompatible Change[​](#backward-incompatible-change-5 "Direct link to Backward Incompatible Change")

- Function `modulo` (operator `%`) with at least one floating point number as argument will calculate remainder of division directly on floating point numbers without converting both arguments to integers. It makes behaviour compatible with most of DBMS. This also applicable for Date and DateTime data types. Added alias `mod`. This closes [#7323](https://github.com/ClickHouse/ClickHouse/issues/7323). [#12585](https://github.com/ClickHouse/ClickHouse/pull/12585) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Deprecate special printing of zero Date/DateTime values as `0000-00-00` and `0000-00-00 00:00:00`. [#12442](https://github.com/ClickHouse/ClickHouse/pull/12442) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- The function `groupArrayMoving*` was not working for distributed queries. It's result was calculated within incorrect data type (without promotion to the largest type). The function `groupArrayMovingAvg` was returning integer number that was inconsistent with the `avg` function. This fixes [#12568](https://github.com/ClickHouse/ClickHouse/issues/12568). [#12622](https://github.com/ClickHouse/ClickHouse/pull/12622) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Add sanity check for MergeTree settings. If the settings are incorrect, the server will refuse to start or to create a table, printing detailed explanation to the user. [#13153](https://github.com/ClickHouse/ClickHouse/pull/13153) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Protect from the cases when user may set `background_pool_size` to value lower than `number_of_free_entries_in_pool_to_execute_mutation` or `number_of_free_entries_in_pool_to_lower_max_size_of_merge`. In these cases ALTERs won't work or the maximum size of merge will be too limited. It will throw exception explaining what to do. This closes [#10897](https://github.com/ClickHouse/ClickHouse/issues/10897). [#12728](https://github.com/ClickHouse/ClickHouse/pull/12728) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- When upgrading from versions older than 20.5, if rolling update is performed and cluster contains both versions 20.5 or greater and less than 20.5, if ClickHouse nodes with old versions are restarted and old version has been started up in presence of newer versions, it may lead to `Part ... intersects previous part` errors. To prevent this error, first install newer clickhouse-server packages on all cluster nodes and then do restarts (so, when clickhouse-server is restarted, it will start up with the new version).

#### New Feature[​](#new-feature-5 "Direct link to New Feature")

- Polygon dictionary type that provides efficient "reverse geocoding" lookups - to find the region by coordinates in a dictionary of many polygons (world map). It is using carefully optimized algorithm with recursive grids to maintain low CPU and memory usage. [#9278](https://github.com/ClickHouse/ClickHouse/pull/9278) ([achulkov2](https://github.com/achulkov2)).
- Added support of LDAP authentication for preconfigured users ("Simple Bind" method). [#11234](https://github.com/ClickHouse/ClickHouse/pull/11234) ([Denis Glazachev](https://github.com/traceon)).
- Introduce setting `alter_partition_verbose_result` which outputs information about touched parts for some types of `ALTER TABLE ... PARTITION ...` queries (currently `ATTACH` and `FREEZE`). Closes [#8076](https://github.com/ClickHouse/ClickHouse/issues/8076). [#13017](https://github.com/ClickHouse/ClickHouse/pull/13017) ([alesapin](https://github.com/alesapin)).
- Add `bayesAB` function for bayesian-ab-testing. [#12327](https://github.com/ClickHouse/ClickHouse/pull/12327) ([achimbab](https://github.com/achimbab)).
- Added `system.crash_log` table into which stack traces for fatal errors are collected. This table should be empty. [#12316](https://github.com/ClickHouse/ClickHouse/pull/12316) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Added http headers `X-ClickHouse-Database` and `X-ClickHouse-Format` which may be used to set default database and output format. [#12981](https://github.com/ClickHouse/ClickHouse/pull/12981) ([hcz](https://github.com/hczhcz)).
- Add `minMap` and `maxMap` functions support to `SimpleAggregateFunction`. [#12662](https://github.com/ClickHouse/ClickHouse/pull/12662) ([Ildus Kurbangaliev](https://github.com/ildus)).
- Add setting `allow_non_metadata_alters` which restricts to execute `ALTER` queries which modify data on disk. Disabled be default. Closes [#11547](https://github.com/ClickHouse/ClickHouse/issues/11547). [#12635](https://github.com/ClickHouse/ClickHouse/pull/12635) ([alesapin](https://github.com/alesapin)).
- A function `formatRow` is added to support turning arbitrary expressions into a string via given format. It's useful for manipulating SQL outputs and is quite versatile combined with the `columns` function. [#12574](https://github.com/ClickHouse/ClickHouse/pull/12574) ([Amos Bird](https://github.com/amosbird)).
- Add `FROM_UNIXTIME` function for compatibility with MySQL, related to [12149](https://github.com/ClickHouse/ClickHouse/issues/12149). [#12484](https://github.com/ClickHouse/ClickHouse/pull/12484) ([flynn](https://github.com/ucasFL)).
- Allow Nullable types as keys in MergeTree tables if `allow_nullable_key` table setting is enabled. Closes [#5319](https://github.com/ClickHouse/ClickHouse/issues/5319). [#12433](https://github.com/ClickHouse/ClickHouse/pull/12433) ([Amos Bird](https://github.com/amosbird)).
- Integration with [COS](https://intl.cloud.tencent.com/product/cos). [#12386](https://github.com/ClickHouse/ClickHouse/pull/12386) ([fastio](https://github.com/fastio)).
- Add `mapAdd` and `mapSubtract` functions for adding/subtracting key-mapped values. [#11735](https://github.com/ClickHouse/ClickHouse/pull/11735) ([Ildus Kurbangaliev](https://github.com/ildus)).

#### Bug Fix[​](#bug-fix-24 "Direct link to Bug Fix")