2023 Changelog

#### New Feature[​](#new-feature-9 "Direct link to New Feature")

- Add a new mode for splitting the work on replicas using settings `parallel_replicas_custom_key` and `parallel_replicas_custom_key_filter_type`. If the cluster consists of a single shard with multiple replicas, up to `max_parallel_replicas` will be randomly picked and turned into shards. For each shard, a corresponding filter is added to the query on the initiator before being sent to the shard. If the cluster consists of multiple shards, it will behave the same as `sample_key` but with the possibility to define an arbitrary key. [#45108](https://github.com/ClickHouse/ClickHouse/pull/45108) ([Antonio Andelic](https://github.com/antonio2368)).
- An option to display partial result on cancel: Added query setting `partial_result_on_first_cancel` allowing the canceled query (e.g. due to Ctrl-C) to return a partial result. [#45689](https://github.com/ClickHouse/ClickHouse/pull/45689) ([Alexey Perevyshin](https://github.com/alexX512)).
- Added support of arbitrary tables engines for temporary tables (except for Replicated and KeeperMap engines). Close [#31497](https://github.com/ClickHouse/ClickHouse/issues/31497). [#46071](https://github.com/ClickHouse/ClickHouse/pull/46071) ([Roman Vasin](https://github.com/rvasin)).
- Add support for replication of user-defined SQL functions using centralized storage in Keeper. [#46085](https://github.com/ClickHouse/ClickHouse/pull/46085) ([Aleksei Filatov](https://github.com/aalexfvk)).
- Implement `system.server_settings` (similar to `system.settings`), which will contain server configurations. [#46550](https://github.com/ClickHouse/ClickHouse/pull/46550) ([pufit](https://github.com/pufit)).
- Support for `UNDROP TABLE` query. Closes [#46811](https://github.com/ClickHouse/ClickHouse/issues/46811). [#47241](https://github.com/ClickHouse/ClickHouse/pull/47241) ([chen](https://github.com/xiedeyantu)).
- Allow separate grants for named collections (e.g. to be able to give `SHOW/CREATE/ALTER/DROP named collection` access only to certain collections, instead of all at once). Closes [#40894](https://github.com/ClickHouse/ClickHouse/issues/40894). Add new access type `NAMED_COLLECTION_CONTROL` which is not given to user default unless explicitly added to the user config (is required to be able to do `GRANT ALL`), also `show_named_collections` is no longer obligatory to be manually specified for user default to be able to have full access rights as was in 23.2. [#46241](https://github.com/ClickHouse/ClickHouse/pull/46241) ([Kseniia Sumarokova](https://github.com/kssenii)).
- Allow nested custom disks. Previously custom disks supported only flat disk structure. [#47106](https://github.com/ClickHouse/ClickHouse/pull/47106) ([Kseniia Sumarokova](https://github.com/kssenii)).
- Introduce a function `widthBucket` (with a `WIDTH_BUCKET` alias for compatibility). [#42974](https://github.com/ClickHouse/ClickHouse/issues/42974). [#46790](https://github.com/ClickHouse/ClickHouse/pull/46790) ([avoiderboi](https://github.com/avoiderboi)).
- Add new function `parseDateTime`/`parseDateTimeInJodaSyntax` according to the specified format string. parseDateTime parses String to DateTime in MySQL syntax, parseDateTimeInJodaSyntax parses in Joda syntax. [#46815](https://github.com/ClickHouse/ClickHouse/pull/46815) ([李扬](https://github.com/taiyang-li)).
- Use `dummy UInt8` for the default structure of table function `null`. Closes [#46930](https://github.com/ClickHouse/ClickHouse/issues/46930). [#47006](https://github.com/ClickHouse/ClickHouse/pull/47006) ([flynn](https://github.com/ucasfl)).
- Support for date format with a comma, like `Dec 15, 2021` in the `parseDateTimeBestEffort` function. Closes [#46816](https://github.com/ClickHouse/ClickHouse/issues/46816). [#47071](https://github.com/ClickHouse/ClickHouse/pull/47071) ([chen](https://github.com/xiedeyantu)).
- Add settings `http_wait_end_of_query` and `http_response_buffer_size` that corresponds to URL params `wait_end_of_query` and `buffer_size` for the HTTP interface. This allows changing these settings in the profiles. [#47108](https://github.com/ClickHouse/ClickHouse/pull/47108) ([Vladimir C](https://github.com/vdimir)).
- Add `system.dropped_tables` table that shows tables that were dropped from `Atomic` databases but were not completely removed yet. [#47364](https://github.com/ClickHouse/ClickHouse/pull/47364) ([chen](https://github.com/xiedeyantu)).
- Add `INSTR` as alias of `positionCaseInsensitive` for MySQL compatibility. Closes [#47529](https://github.com/ClickHouse/ClickHouse/issues/47529). [#47535](https://github.com/ClickHouse/ClickHouse/pull/47535) ([flynn](https://github.com/ucasfl)).
- Added `toDecimalString` function allowing to convert numbers to string with fixed precision. [#47838](https://github.com/ClickHouse/ClickHouse/pull/47838) ([Andrey Zvonov](https://github.com/zvonand)).
- Add a merge tree setting `max_number_of_mutations_for_replica`. It limits the number of part mutations per replica to the specified amount. Zero means no limit on the number of mutations per replica (the execution can still be constrained by other settings). [#48047](https://github.com/ClickHouse/ClickHouse/pull/48047) ([Vladimir C](https://github.com/vdimir)).
- Add the Map-related function `mapFromArrays`, which allows the creation of a map from a pair of arrays. [#31125](https://github.com/ClickHouse/ClickHouse/pull/31125) ([李扬](https://github.com/taiyang-li)).
- Allow control of compression in Parquet/ORC/Arrow output formats, adds support for more compression input formats. This closes [#13541](https://github.com/ClickHouse/ClickHouse/issues/13541). [#47114](https://github.com/ClickHouse/ClickHouse/pull/47114) ([Kruglov Pavel](https://github.com/Avogar)).
- Add SSL User Certificate authentication to the native protocol. Closes [#47077](https://github.com/ClickHouse/ClickHouse/issues/47077). [#47596](https://github.com/ClickHouse/ClickHouse/pull/47596) ([Nikolay Degterinsky](https://github.com/evillique)).
- Add \*OrNull() and \*OrZero() variants for `parseDateTime`, add alias `str_to_date` for MySQL parity. [#48000](https://github.com/ClickHouse/ClickHouse/pull/48000) ([Robert Schulze](https://github.com/rschu1ze)).
- Added operator `REGEXP` (similar to operators "LIKE", "IN", "MOD" etc.) for better compatibility with MySQL [#47869](https://github.com/ClickHouse/ClickHouse/pull/47869) ([Robert Schulze](https://github.com/rschu1ze)).

#### Performance Improvement[​](#performance-improvement-9 "Direct link to Performance Improvement")