2023 Changelog

#### New Feature[​](#new-feature-2 "Direct link to New Feature")

- Add function `arrayFold(accumulator, x1, ..., xn -> expression, initial, array1, ..., arrayn)` which applies a lambda function to multiple arrays of the same cardinality and collects the result in an accumulator. [#49794](https://github.com/ClickHouse/ClickHouse/pull/49794) ([Lirikl](https://github.com/Lirikl)).
- Support for `Npy` format. `SELECT * FROM file('example_array.npy', Npy)`. [#55982](https://github.com/ClickHouse/ClickHouse/pull/55982) ([Yarik Briukhovetskyi](https://github.com/yariks5s)).
- If a table has a space-filling curve in its key, e.g., `ORDER BY mortonEncode(x, y)`, the conditions on its arguments, e.g., `x >= 10 AND x <= 20 AND y >= 20 AND y <= 30` can be used for indexing. A setting `analyze_index_with_space_filling_curves` is added to enable or disable this analysis. This closes [#41195](https://github.com/ClickHouse/ClickHouse/issue/41195). Continuation of [#4538](https://github.com/ClickHouse/ClickHouse/pull/4538). Continuation of [#6286](https://github.com/ClickHouse/ClickHouse/pull/6286). Continuation of [#28130](https://github.com/ClickHouse/ClickHouse/pull/28130). Continuation of [#41753](https://github.com/ClickHouse/ClickHouse/pull/#41753). [#55642](https://github.com/ClickHouse/ClickHouse/pull/55642) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
- A new setting called `force_optimize_projection_name`, it takes a name of projection as an argument. If it's value set to a non-empty string, ClickHouse checks that this projection is used in the query at least once. Closes [#55331](https://github.com/ClickHouse/ClickHouse/issues/55331). [#56134](https://github.com/ClickHouse/ClickHouse/pull/56134) ([Yarik Briukhovetskyi](https://github.com/yariks5s)).
- Support asynchronous inserts with external data via native protocol. Previously it worked only if data is inlined into query. [#54730](https://github.com/ClickHouse/ClickHouse/pull/54730) ([Anton Popov](https://github.com/CurtizJ)).
- Added aggregation function `lttb` which uses the [Largest-Triangle-Three-Buckets](https://skemman.is/bitstream/1946/15343/3/SS_MSthesis.pdf) algorithm for downsampling data for visualization. [#53145](https://github.com/ClickHouse/ClickHouse/pull/53145) ([Sinan](https://github.com/sinsinan)).
- Query`CHECK TABLE` has better performance and usability (sends progress updates, cancellable). Support checking particular part with `CHECK TABLE ... PART 'part_name'`. [#53404](https://github.com/ClickHouse/ClickHouse/pull/53404) ([vdimir](https://github.com/vdimir)).
- Added function `jsonMergePatch`. When working with JSON data as strings, it provides a way to merge these strings (of JSON objects) together to form a single string containing a single JSON object. [#54364](https://github.com/ClickHouse/ClickHouse/pull/54364) ([Memo](https://github.com/Joeywzr)).
- The second part of Kusto Query Language dialect support. [Phase 1 implementation](https://github.com/ClickHouse/ClickHouse/pull/37961)  has been merged. [#42510](https://github.com/ClickHouse/ClickHouse/pull/42510) ([larryluogit](https://github.com/larryluogit)).
- Added a new SQL function, `arrayRandomSample(arr, k)` which returns a sample of k elements from the input array. Similar functionality could previously be achieved only with less convenient syntax, e.g. "SELECT arrayReduce('groupArraySample(3)', range(10))". [#54391](https://github.com/ClickHouse/ClickHouse/pull/54391) ([itayisraelov](https://github.com/itayisraelov)).
- Introduce `-ArgMin`/`-ArgMax` aggregate combinators which allow to aggregate by min/max values only. One use case can be found in [#54818](https://github.com/ClickHouse/ClickHouse/issues/54818). This PR also reorganize combinators into dedicated folder. [#54947](https://github.com/ClickHouse/ClickHouse/pull/54947) ([Amos Bird](https://github.com/amosbird)).
- Allow to drop cache for Protobuf format with `SYSTEM DROP SCHEMA FORMAT CACHE [FOR Protobuf]`. [#55064](https://github.com/ClickHouse/ClickHouse/pull/55064) ([Aleksandr Musorin](https://github.com/AVMusorin)).
- Add external HTTP Basic authenticator. [#55199](https://github.com/ClickHouse/ClickHouse/pull/55199) ([Aleksei Filatov](https://github.com/aalexfvk)).
- Added function `byteSwap` which reverses the bytes of unsigned integers. This is particularly useful for reversing values of types which are represented as unsigned integers internally such as IPv4. [#55211](https://github.com/ClickHouse/ClickHouse/pull/55211) ([Priyansh Agrawal](https://github.com/Priyansh121096)).
- Added function `formatQuery` which returns a formatted version (possibly spanning multiple lines) of a SQL query string. Also added function `formatQuerySingleLine` which does the same but the returned string will not contain linebreaks. [#55239](https://github.com/ClickHouse/ClickHouse/pull/55239) ([Salvatore Mesoraca](https://github.com/aiven-sal)).
- Added `DWARF` input format that reads debug symbols from an ELF executable/library/object file. [#55450](https://github.com/ClickHouse/ClickHouse/pull/55450) ([Michael Kolupaev](https://github.com/al13n321)).
- Allow to save unparsed records and errors in RabbitMQ, NATS and FileLog engines. Add virtual columns `_error` and `_raw_message`(for NATS and RabbitMQ), `_raw_record` (for FileLog) that are filled when ClickHouse fails to parse new record. The behaviour is controlled under storage settings `nats_handle_error_mode` for NATS, `rabbitmq_handle_error_mode` for RabbitMQ, `handle_error_mode` for FileLog similar to `kafka_handle_error_mode`. If it's set to `default`, en exception will be thrown when ClickHouse fails to parse a record, if it's set to `stream`, erorr and raw record will be saved into virtual columns. Closes [#36035](https://github.com/ClickHouse/ClickHouse/issues/36035). [#55477](https://github.com/ClickHouse/ClickHouse/pull/55477) ([Kruglov Pavel](https://github.com/Avogar)).
- Keeper client improvement: add `get_all_children_number command` that returns number of all children nodes under a specific path. [#55485](https://github.com/ClickHouse/ClickHouse/pull/55485) ([guoxiaolong](https://github.com/guoxiaolongzte)).
- Keeper client improvement: add `get_direct_children_number` command that returns number of direct children nodes under a path. [#55898](https://github.com/ClickHouse/ClickHouse/pull/55898) ([xuzifu666](https://github.com/xuzifu666)).
- Add statement `SHOW SETTING setting_name` which is a simpler version of existing statement `SHOW SETTINGS`. [#55979](https://github.com/ClickHouse/ClickHouse/pull/55979) ([Maksim Kita](https://github.com/kitaisreal)).
- Added fields `substreams` and `filenames` to the `system.parts_columns` table. [#55108](https://github.com/ClickHouse/ClickHouse/pull/55108) ([Anton Popov](https://github.com/CurtizJ)).
- Add support for `SHOW MERGES` query. [#55815](https://github.com/ClickHouse/ClickHouse/pull/55815) ([megao](https://github.com/jetgm)).
- Introduce a setting `create_table_empty_primary_key_by_default` for default `ORDER BY ()`. [#55899](https://github.com/ClickHouse/ClickHouse/pull/55899) ([Srikanth Chekuri](https://github.com/srikanthccv)).

#### Performance Improvement[​](#performance-improvement-2 "Direct link to Performance Improvement")