2023 Changelog

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

- Added `Overlay` database engine to combine multiple databases into one. Added `Filesystem` database engine to represent a directory in the filesystem as a set of implicitly available tables with auto-detected formats and structures. A new `S3` database engine allows to read-only interact with s3 storage by representing a prefix as a set of tables. A new `HDFS` database engine allows to interact with HDFS storage in the same way. [#48821](https://github.com/ClickHouse/ClickHouse/pull/48821) ([alekseygolub](https://github.com/alekseygolub)).
- Add support for external disks in Keeper for storing snapshots and logs. [#50098](https://github.com/ClickHouse/ClickHouse/pull/50098) ([Antonio Andelic](https://github.com/antonio2368)).
- Add support for multi-directory selection (`{}`) globs. [#50559](https://github.com/ClickHouse/ClickHouse/pull/50559) ([Andrey Zvonov](https://github.com/zvonand)).
- Kafka connector can fetch Avro schema from schema registry with basic authentication using url-encoded credentials. [#49664](https://github.com/ClickHouse/ClickHouse/pull/49664) ([Ilya Golshtein](https://github.com/ilejn)).
- Add function `arrayJaccardIndex` which computes the Jaccard similarity between two arrays. [#50076](https://github.com/ClickHouse/ClickHouse/pull/50076) ([FFFFFFFHHHHHHH](https://github.com/FFFFFFFHHHHHHH)).
- Add a column `is_obsolete` to `system.settings` and similar tables. Closes [#50819](https://github.com/ClickHouse/ClickHouse/issues/50819). [#50826](https://github.com/ClickHouse/ClickHouse/pull/50826) ([flynn](https://github.com/ucasfl)).
- Implement support of encrypted elements in configuration file. Added possibility to use encrypted text in leaf elements of configuration file. The text is encrypted using encryption codecs from `<encryption_codecs>` section. [#50986](https://github.com/ClickHouse/ClickHouse/pull/50986) ([Roman Vasin](https://github.com/rvasin)).
- Grace Hash Join algorithm is now applicable to FULL and RIGHT JOINs. [#49483](https://github.com/ClickHouse/ClickHouse/issues/49483). [#51013](https://github.com/ClickHouse/ClickHouse/pull/51013) ([lgbo](https://github.com/lgbo-ustc)).
- Add `SYSTEM STOP LISTEN` query for more graceful termination. Closes [#47972](https://github.com/ClickHouse/ClickHouse/issues/47972). [#51016](https://github.com/ClickHouse/ClickHouse/pull/51016) ([Nikolay Degterinsky](https://github.com/evillique)).
- Add `input_format_csv_allow_variable_number_of_columns` options. [#51273](https://github.com/ClickHouse/ClickHouse/pull/51273) ([Dmitry Kardymon](https://github.com/kardymonds)).
- Another boring feature: add function `substring_index`, as in Spark or MySQL. [#51472](https://github.com/ClickHouse/ClickHouse/pull/51472) ([李扬](https://github.com/taiyang-li)).
- A system table `jemalloc_bins` to show stats for jemalloc bins. Example `SELECT *, size * (nmalloc - ndalloc) AS allocated_bytes FROM system.jemalloc_bins WHERE allocated_bytes > 0 ORDER BY allocated_bytes DESC LIMIT 10`. Enjoy. [#51674](https://github.com/ClickHouse/ClickHouse/pull/51674) ([Alexander Gololobov](https://github.com/davenger)).
- Add `RowBinaryWithDefaults` format with extra byte before each column as a flag for using the column's default value. Closes [#50854](https://github.com/ClickHouse/ClickHouse/issues/50854). [#51695](https://github.com/ClickHouse/ClickHouse/pull/51695) ([Kruglov Pavel](https://github.com/Avogar)).
- Added `default_temporary_table_engine` setting. Same as `default_table_engine` but for temporary tables. [#51292](https://github.com/ClickHouse/ClickHouse/issues/51292). [#51708](https://github.com/ClickHouse/ClickHouse/pull/51708) ([velavokr](https://github.com/velavokr)).
- Added new `initcap` / `initcapUTF8` functions which convert the first letter of each word to upper case and the rest to lower case. [#51735](https://github.com/ClickHouse/ClickHouse/pull/51735) ([Dmitry Kardymon](https://github.com/kardymonds)).
- Create table now supports `PRIMARY KEY` syntax in column definition. Columns are added to primary index in the same order columns are defined. [#51881](https://github.com/ClickHouse/ClickHouse/pull/51881) ([Ilya Yatsishin](https://github.com/qoega)).
- Added the possibility to use date and time format specifiers in log and error log file names, either in config files (`log` and `errorlog` tags) or command line arguments (`--log-file` and `--errorlog-file`). [#51945](https://github.com/ClickHouse/ClickHouse/pull/51945) ([Victor Krasnov](https://github.com/sirvickr)).
- Added Peak Memory Usage statistic to HTTP headers. [#51946](https://github.com/ClickHouse/ClickHouse/pull/51946) ([Dmitry Kardymon](https://github.com/kardymonds)).
- Added new `hasSubsequence` (+`CaseInsensitive` and `UTF8` versions) functions to match subsequences in strings. [#52050](https://github.com/ClickHouse/ClickHouse/pull/52050) ([Dmitry Kardymon](https://github.com/kardymonds)).
- Add `array_agg` as alias of `groupArray` for PostgreSQL compatibility. Closes [#52100](https://github.com/ClickHouse/ClickHouse/issues/52100). ### Documentation entry for user-facing changes. [#52135](https://github.com/ClickHouse/ClickHouse/pull/52135) ([flynn](https://github.com/ucasfl)).
- Add `any_value` as a compatibility alias for `any` aggregate function. Closes [#52140](https://github.com/ClickHouse/ClickHouse/issues/52140). [#52147](https://github.com/ClickHouse/ClickHouse/pull/52147) ([flynn](https://github.com/ucasfl)).
- Add aggregate function `array_concat_agg` for compatibility with BigQuery, it's alias of `groupArrayArray`. Closes [#52139](https://github.com/ClickHouse/ClickHouse/issues/52139). [#52149](https://github.com/ClickHouse/ClickHouse/pull/52149) ([flynn](https://github.com/ucasfl)).
- Add `OCTET_LENGTH` as an alias to `length`. Closes [#52153](https://github.com/ClickHouse/ClickHouse/issues/52153). [#52176](https://github.com/ClickHouse/ClickHouse/pull/52176) ([FFFFFFFHHHHHHH](https://github.com/FFFFFFFHHHHHHH)).
- Added `firstLine` function to extract the first line from the multi-line string. This closes [#51172](https://github.com/ClickHouse/ClickHouse/issues/51172). [#52209](https://github.com/ClickHouse/ClickHouse/pull/52209) ([Mikhail Koviazin](https://github.com/mkmkme)).
- Implement KQL-style formatting for the `Interval` data type. This is only needed for compatibility with the `Kusto` query language. [#45671](https://github.com/ClickHouse/ClickHouse/pull/45671) ([ltrk2](https://github.com/ltrk2)).
- Added query `SYSTEM FLUSH ASYNC INSERT QUEUE` which flushes all pending asynchronous inserts to the destination tables. Added a server-side setting `async_insert_queue_flush_on_shutdown` (`true` by default) which determines whether to flush queue of asynchronous inserts on graceful shutdown. Setting `async_insert_threads` is now a server-side setting. [#49160](https://github.com/ClickHouse/ClickHouse/pull/49160) ([Anton Popov](https://github.com/CurtizJ)).
- Aliases `current_database` and a new function `current_schemas` for compatibility with PostgreSQL. [#51076](https://github.com/ClickHouse/ClickHouse/pull/51076) ([Pedro Riera](https://github.com/priera)).
- Add alias for functions `today` (now available under the `curdate`/`current_date` names) and `now` (`current_timestamp`). [#52106](https://github.com/ClickHouse/ClickHouse/pull/52106) ([Lloyd-Pottiger](https://github.com/Lloyd-Pottiger)).
- Support `async_deduplication_token` for async insert. [#52136](https://github.com/ClickHouse/ClickHouse/pull/52136) ([Han Fei](https://github.com/hanfei1991)).
- Add new setting `disable_url_encoding` that allows to disable decoding/encoding path in uri in URL engine. [#52337](https://github.com/ClickHouse/ClickHouse/pull/52337) ([Kruglov Pavel](https://github.com/Avogar)).

#### Performance Improvement[​](#performance-improvement-5 "Direct link to Performance Improvement")