### Table of Contents
**[ClickHouse release v24.1, 2024-01-30](#241)**<br/>
**[Changelog for 2023](https://clickhouse.com/docs/en/whats-new/changelog/2023/)**<br/>

# 2024 Changelog

### <a id="241"></a> ClickHouse release 24.1, 2024-01-30

#### Backward Incompatible Change
* The setting `print_pretty_type_names` is turned on by default. You can turn it off to keep the old behavior or `SET compatibility = '23.12'`. [#57726](https://github.com/ClickHouse/ClickHouse/pull/57726) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* The MergeTree setting `clean_deleted_rows` is deprecated, it has no effect anymore. The `CLEANUP` keyword for `OPTIMIZE` is not allowed by default (unless `allow_experimental_replacing_merge_with_cleanup` is enabled). [#58316](https://github.com/ClickHouse/ClickHouse/pull/58316) ([Alexander Tokmakov](https://github.com/tavplubix)).
* The function `reverseDNSQuery` is no longer available. This closes [#58368](https://github.com/ClickHouse/ClickHouse/issues/58368). [#58369](https://github.com/ClickHouse/ClickHouse/pull/58369) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Enable various changes to improve the access control in the configuration file. These changes affect the behavior, and you check the `config.xml` in the `access_control_improvements` section. In case you are not confident, keep the values in the configuration file as they were in the previous version. [#58584](https://github.com/ClickHouse/ClickHouse/pull/58584) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Improve the operation of `sumMapFiltered` with NaN values. NaN values are now placed at the end (instead of randomly) and considered different from any values. `-0` is now also treated as equal to `0`; since 0 values are discarded, `-0` values are discarded too. [#58959](https://github.com/ClickHouse/ClickHouse/pull/58959) ([Raúl Marín](https://github.com/Algunenano)).
* The function `visibleWidth` will behave according to the docs. In previous versions, it simply counted code points after string serialization, like the `lengthUTF8` function, but didn't consider zero-width and combining characters, full-width characters, tabs, and deletes. Now the behavior is changed accordingly. If you want to keep the old behavior, set `function_visible_width_behavior` to `0`, or set `compatibility` to `23.12` or lower. [#59022](https://github.com/ClickHouse/ClickHouse/pull/59022) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* `Kusto` dialect is disabled until these two bugs will be fixed: [#59037](https://github.com/ClickHouse/ClickHouse/issues/59037) and [#59036](https://github.com/ClickHouse/ClickHouse/issues/59036). [#59305](https://github.com/ClickHouse/ClickHouse/pull/59305) ([Alexey Milovidov](https://github.com/alexey-milovidov)). Any attempt to use `Kusto` will result in exception.
* More efficient implementation of the `FINAL` modifier no longer guarantees preserving the order even if `max_threads = 1`. If you counted on the previous behavior, set `enable_vertical_final` to 0 or `compatibility` to `23.12`. 

#### New Feature
* Implement Variant data type that represents a union of other data types. Type `Variant(T1, T2, ..., TN)` means that each row of this type has a value of either type `T1` or `T2` or ... or `TN` or none of them (`NULL` value). Variant type is available under a setting `allow_experimental_variant_type`. Reference: [#54864](https://github.com/ClickHouse/ClickHouse/issues/54864). [#58047](https://github.com/ClickHouse/ClickHouse/pull/58047) ([Kruglov Pavel](https://github.com/Avogar)).
* Certain settings (currently `min_compress_block_size` and `max_compress_block_size`) can now be specified at column-level where they take precedence over the corresponding table-level setting. Example: `CREATE TABLE tab (col String SETTINGS (min_compress_block_size = 81920, max_compress_block_size = 163840)) ENGINE = MergeTree ORDER BY tuple();`. [#55201](https://github.com/ClickHouse/ClickHouse/pull/55201) ([Duc Canh Le](https://github.com/canhld94)).
* Add `quantileDD` aggregate function as well as the corresponding `quantilesDD` and `medianDD`. It is based on the DDSketch https://www.vldb.org/pvldb/vol12/p2195-masson.pdf. ### Documentation entry for user-facing changes. [#56342](https://github.com/ClickHouse/ClickHouse/pull/56342) ([Srikanth Chekuri](https://github.com/srikanthccv)).
* Allow to configure any kind of object storage with any kind of metadata type. [#58357](https://github.com/ClickHouse/ClickHouse/pull/58357) ([Kseniia Sumarokova](https://github.com/kssenii)).
* Added `null_status_on_timeout_only_active` and `throw_only_active` modes for `distributed_ddl_output_mode` that allow to avoid waiting for inactive replicas. [#58350](https://github.com/ClickHouse/ClickHouse/pull/58350) ([Alexander Tokmakov](https://github.com/tavplubix)).
* Add function `arrayShingles` to compute subarrays, e.g. `arrayShingles([1, 2, 3, 4, 5], 3)` returns `[[1,2,3],[2,3,4],[3,4,5]]`. [#58396](https://github.com/ClickHouse/ClickHouse/pull/58396) ([Zheng Miao](https://github.com/zenmiao7)).
* Added functions `punycodeEncode`, `punycodeDecode`, `idnaEncode` and `idnaDecode` which are useful for translating international domain names to an ASCII representation according to the IDNA standard. [#58454](https://github.com/ClickHouse/ClickHouse/pull/58454) ([Robert Schulze](https://github.com/rschu1ze)).
* Added string similarity functions `dramerauLevenshteinDistance`, `jaroSimilarity` and `jaroWinklerSimilarity`. [#58531](https://github.com/ClickHouse/ClickHouse/pull/58531) ([Robert Schulze](https://github.com/rschu1ze)).
* Add two settings `output_format_compression_level` to change output compression level and `output_format_compression_zstd_window_log` to explicitly set compression window size and enable long-range mode for zstd compression if output compression method is `zstd`. Applied for `INTO OUTFILE` and when writing to table functions `file`, `url`, `hdfs`, `s3`, and `azureBlobStorage`. [#58539](https://github.com/ClickHouse/ClickHouse/pull/58539) ([Duc Canh Le](https://github.com/canhld94)).
* Automatically disable ANSI escape sequences in Pretty formats if the output is not a terminal. Add new `auto` mode to setting `output_format_pretty_color`. [#58614](https://github.com/ClickHouse/ClickHouse/pull/58614) ([Shaun Struwig](https://github.com/Blargian)).
* Added function `sqidDecode` which decodes [Sqids](https://sqids.org/). [#58544](https://github.com/ClickHouse/ClickHouse/pull/58544) ([Robert Schulze](https://github.com/rschu1ze)).
* Allow to read Bool values into String in JSON input formats. It's done under a setting `input_format_json_read_bools_as_strings` that is enabled by default. [#58561](https://github.com/ClickHouse/ClickHouse/pull/58561) ([Kruglov Pavel](https://github.com/Avogar)).
* Added function `seriesDecomposeSTL` which decomposes a time series into a season, a trend and a residual component. [#57078](https://github.com/ClickHouse/ClickHouse/pull/57078) ([Bhavna Jindal](https://github.com/bhavnajindal)).
* Introduced MySQL Binlog Client for MaterializedMySQL: One binlog connection for many databases. [#57323](https://github.com/ClickHouse/ClickHouse/pull/57323) ([Val Doroshchuk](https://github.com/valbok)).
* Intel QuickAssist Technology (QAT) provides hardware-accelerated compression and cryptograpy. ClickHouse got a new compression codec `ZSTD_QAT` which utilizes QAT for zstd compression. The codec uses [Intel's QATlib](https://github.com/intel/qatlib) and [Inte's QAT ZSTD Plugin](https://github.com/intel/QAT-ZSTD-Plugin). Right now, only compression can be accelerated in hardware (a software fallback kicks in in case QAT could not be initialized), decompression always runs in software. [#57509](https://github.com/ClickHouse/ClickHouse/pull/57509) ([jasperzhu](https://github.com/jinjunzh)).
* Implementing the new way how object storage keys are generated for s3 disks. Now the format could be defined in terms of `re2` regex syntax with `key_template` option in disc description. [#57663](https://github.com/ClickHouse/ClickHouse/pull/57663) ([Sema Checherinda](https://github.com/CheSema)).
* Table system.dropped_tables_parts contains parts of system.dropped_tables tables (dropped but not yet removed tables). [#58038](https://github.com/ClickHouse/ClickHouse/pull/58038) ([Yakov Olkhovskiy](https://github.com/yakov-olkhovskiy)).
* Add settings `max_materialized_views_size_for_table` to limit the number of materialized views attached to a table. [#58068](https://github.com/ClickHouse/ClickHouse/pull/58068) ([zhongyuankai](https://github.com/zhongyuankai)).
* `clickhouse-format` improvements: support INSERT queries with `VALUES`; support comments (use `--comments` to output them); support `--max_line_length` option to format only long queries in multiline. [#58246](https://github.com/ClickHouse/ClickHouse/pull/58246) ([vdimir](https://github.com/vdimir)).
* Attach all system tables in `clickhouse-local`, including `system.parts`. This closes [#58312](https://github.com/ClickHouse/ClickHouse/issues/58312). [#58359](https://github.com/ClickHouse/ClickHouse/pull/58359) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Support for `Enum` data types in function `transform`. This closes [#58241](https://github.com/ClickHouse/ClickHouse/issues/58241). [#58360](https://github.com/ClickHouse/ClickHouse/pull/58360) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Add table `system.database_engines`. [#58390](https://github.com/ClickHouse/ClickHouse/pull/58390) ([Bharat Nallan](https://github.com/bharatnc)). Allow registering database engines independently in the codebase. [#58365](https://github.com/ClickHouse/ClickHouse/pull/58365) ([Bharat Nallan](https://github.com/bharatnc)). Allow registering interpreters independently. [#58443](https://github.com/ClickHouse/ClickHouse/pull/58443) ([Bharat Nallan](https://github.com/bharatnc)).
* Added `FROM <Replicas>` modifier for `SYSTEM SYNC REPLICA LIGHTWEIGHT` query. With the `FROM` modifier ensures we wait for fetches and drop-ranges only for the specified source replicas, as well as any replica not in zookeeper or with an empty source_replica. [#58393](https://github.com/ClickHouse/ClickHouse/pull/58393) ([Jayme Bird](https://github.com/jaymebrd)).
* Added setting `update_insert_deduplication_token_in_dependent_materialized_views`. This setting allows to update insert deduplication token with table identifier during insert in dependent materialized views. Closes [#59165](https://github.com/ClickHouse/ClickHouse/issues/59165). [#59238](https://github.com/ClickHouse/ClickHouse/pull/59238) ([Maksim Kita](https://github.com/kitaisreal)).
* Added statement `SYSTEM RELOAD ASYNCHRONOUS METRICS` which updates the asynchronous metrics. Mostly useful for testing and development. [#53710](https://github.com/ClickHouse/ClickHouse/pull/53710) ([Robert Schulze](https://github.com/rschu1ze)).

#### Performance Improvement
* Coordination for parallel replicas is rewritten for better parallelism and cache locality. It has been tested for linear scalability on hundreds of replicas. It also got support for reading in order. [#57968](https://github.com/ClickHouse/ClickHouse/pull/57968) ([Nikita Taranov](https://github.com/nickitat)).
* Replace HTTP outgoing buffering based with the native ClickHouse buffers. Add bytes counting metrics for interfaces. [#56064](https://github.com/ClickHouse/ClickHouse/pull/56064) ([Yakov Olkhovskiy](https://github.com/yakov-olkhovskiy)).
* Large aggregation states of `uniqExact` will be merged in parallel in distrubuted queries. [#59009](https://github.com/ClickHouse/ClickHouse/pull/59009) ([Nikita Taranov](https://github.com/nickitat)).
* Lower memory usage after reading from `MergeTree` tables. [#59290](https://github.com/ClickHouse/ClickHouse/pull/59290) ([Anton Popov](https://github.com/CurtizJ)).
* Lower memory usage in vertical merges. [#59340](https://github.com/ClickHouse/ClickHouse/pull/59340) ([Anton Popov](https://github.com/CurtizJ)).
* Avoid huge memory consumption during Keeper startup for more cases. [#58455](https://github.com/ClickHouse/ClickHouse/pull/58455) ([Antonio Andelic](https://github.com/antonio2368)).
* Keeper improvement: reduce Keeper's memory usage for stored nodes. [#59002](https://github.com/ClickHouse/ClickHouse/pull/59002) ([Antonio Andelic](https://github.com/antonio2368)).
* More cache-friendly final implementation. Note on the behaviour change: previously queries with `FINAL` modifier that read with a single stream (e.g. `max_threads = 1`) produced sorted output without explicitly provided `ORDER BY` clause. This is no longer guaranteed when `enable_vertical_final = true` (and it is so by default). [#54366](https://github.com/ClickHouse/ClickHouse/pull/54366) ([Duc Canh Le](https://github.com/canhld94)).
* Bypass extra copying in `ReadBufferFromIStream` which is used, e.g., for reading from S3. [#56961](https://github.com/ClickHouse/ClickHouse/pull/56961) ([Nikita Taranov](https://github.com/nickitat)).
* Optimize array element function when input is Array(Map)/Array(Array(Num)/Array(Array(String))/Array(BigInt)/Array(Decimal). The previous implementations did more allocations than needed. The optimization speed up is up to ~6x especially when input type is Array(Map). [#56403](https://github.com/ClickHouse/ClickHouse/pull/56403) ([李扬](https://github.com/taiyang-li)).
* Read column once while reading more than one subcolumn from it in compact parts. [#57631](https://github.com/ClickHouse/ClickHouse/pull/57631) ([Kruglov Pavel](https://github.com/Avogar)).
* Rewrite the AST of `sum(column + constant)` function. This is available as an optimization pass for Analyzer [#57853](https://github.com/ClickHouse/ClickHouse/pull/57853) ([Jiebin Sun](https://github.com/jiebinn)).
* The evaluation of function `match` now utilizes skipping indices `ngrambf_v1` and `tokenbf_v1`. [#57882](https://github.com/ClickHouse/ClickHouse/pull/57882) ([凌涛](https://github.com/lingtaolf)).
* The evaluation of function `match` now utilizes inverted indices. [#58284](https://github.com/ClickHouse/ClickHouse/pull/58284) ([凌涛](https://github.com/lingtaolf)).
* MergeTree `FINAL` does not compare rows from same non-L0 part. [#58142](https://github.com/ClickHouse/ClickHouse/pull/58142) ([Duc Canh Le](https://github.com/canhld94)).
* Speed up iota calls (filling array with consecutive numbers). [#58271](https://github.com/ClickHouse/ClickHouse/pull/58271) ([Raúl Marín](https://github.com/Algunenano)).
* Speedup MIN/MAX for non-numeric types. [#58334](https://github.com/ClickHouse/ClickHouse/pull/58334) ([Raúl Marín](https://github.com/Algunenano)).
* Optimize the combination of filters (like in multi-stage PREWHERE) with BMI2/SSE intrinsics [#58800](https://github.com/ClickHouse/ClickHouse/pull/58800) ([Zhiguo Zhou](https://github.com/ZhiguoZh)).
* Use one thread less in `clickhouse-local`. [#58968](https://github.com/ClickHouse/ClickHouse/pull/58968) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Improve the `multiIf` function performance when the type is Nullable. [#57745](https://github.com/ClickHouse/ClickHouse/pull/57745) ([KevinyhZou](https://github.com/KevinyhZou)).
* Add `SYSTEM JEMALLOC PURGE` for purging unused jemalloc pages, `SYSTEM JEMALLOC [ ENABLE | DISABLE | FLUSH ] PROFILE` for controlling jemalloc profile if the profiler is enabled. Add jemalloc-related 4LW command in Keeper: `jmst` for dumping jemalloc stats, `jmfp`, `jmep`, `jmdp` for controlling jemalloc profile if the profiler is enabled. [#58665](https://github.com/ClickHouse/ClickHouse/pull/58665) ([Antonio Andelic](https://github.com/antonio2368)).
* Lower memory consumption in backups to S3. [#58962](https://github.com/ClickHouse/ClickHouse/pull/58962) ([Vitaly Baranov](https://github.com/vitlibar)).

#### Improvement
* Added comments (brief descriptions) to all columns of system tables. There are several reasons for this: - We use system tables a lot, and sometimes it could be very difficult for developer to understand the purpose and the meaning of a particular column. - We change (add new ones or modify existing) system tables a lot and the documentation for them is always outdated. For example take a look at the documentation page for [`system.parts`](https://clickhouse.com/docs/en/operations/system-tables/parts). It misses a lot of columns - We would like to eventually generate documentation directly from ClickHouse. [#58356](https://github.com/ClickHouse/ClickHouse/pull/58356) ([Nikita Mikhaylov](https://github.com/nikitamikhaylov)).
* Allow queries without aliases for subqueries for `PASTE JOIN`. [#58654](https://github.com/ClickHouse/ClickHouse/pull/58654) ([Yarik Briukhovetskyi](https://github.com/yariks5s)).
* Enable `MySQL`/`MariaDB` integration on macOS. This closes [#21191](https://github.com/ClickHouse/ClickHouse/issues/21191). [#46316](https://github.com/ClickHouse/ClickHouse/pull/46316) ([Alexey Milovidov](https://github.com/alexey-milovidov)) ([Robert Schulze](https://github.com/rschu1ze)).
* Disable `max_rows_in_set_to_optimize_join` by default. [#56396](https://github.com/ClickHouse/ClickHouse/pull/56396) ([vdimir](https://github.com/vdimir)).
* Add `<host_name>` config parameter that allows avoiding resolving hostnames in ON CLUSTER DDL queries and Replicated database engines. This mitigates the possibility of the queue being stuck in case of a change in cluster definition. Closes [#57573](https://github.com/ClickHouse/ClickHouse/issues/57573). [#57603](https://github.com/ClickHouse/ClickHouse/pull/57603) ([Nikolay Degterinsky](https://github.com/evillique)).
* Increase `load_metadata_threads` to 16 for the filesystem cache. It will make the server start up faster. [#57732](https://github.com/ClickHouse/ClickHouse/pull/57732) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Add ability to throttle merges/mutations (`max_mutations_bandwidth_for_server`/`max_merges_bandwidth_for_server`). [#57877](https://github.com/ClickHouse/ClickHouse/pull/57877) ([Azat Khuzhin](https://github.com/azat)).
* Replaced undocumented (boolean) column `is_hot_reloadable` in system table `system.server_settings` by (Enum8) column `changeable_without_restart` with possible values `No`, `Yes`, `IncreaseOnly` and `DecreaseOnly`. Also documented the column. [#58029](https://github.com/ClickHouse/ClickHouse/pull/58029) ([skyoct](https://github.com/skyoct)).
* Cluster discovery supports setting username and password, close [#58063](https://github.com/ClickHouse/ClickHouse/issues/58063). [#58123](https://github.com/ClickHouse/ClickHouse/pull/58123) ([vdimir](https://github.com/vdimir)).
* Support query parameters in `ALTER TABLE ... PART`. [#58297](https://github.com/ClickHouse/ClickHouse/pull/58297) ([Azat Khuzhin](https://github.com/azat)).
* Create consumers for Kafka tables on the fly (but keep them for some period - `kafka_consumers_pool_ttl_ms`, since last used), this should fix problem with statistics for `system.kafka_consumers` (that does not consumed when nobody reads from Kafka table, which leads to live memory leak and slow table detach) and also this PR enables stats for `system.kafka_consumers` by default again. [#58310](https://github.com/ClickHouse/ClickHouse/pull/58310) ([Azat Khuzhin](https://github.com/azat)).
* `sparkBar` as an alias to `sparkbar`. [#58335](https://github.com/ClickHouse/ClickHouse/pull/58335) ([凌涛](https://github.com/lingtaolf)).
* Avoid sending `ComposeObject` requests after upload to `GCS`. [#58343](https://github.com/ClickHouse/ClickHouse/pull/58343) ([Azat Khuzhin](https://github.com/azat)).
* Correctly handle keys with dot in the name in configurations XMLs. [#58354](https://github.com/ClickHouse/ClickHouse/pull/58354) ([Azat Khuzhin](https://github.com/azat)).
* Make function `format` return constant on constant arguments. This closes [#58355](https://github.com/ClickHouse/ClickHouse/issues/58355). [#58358](https://github.com/ClickHouse/ClickHouse/pull/58358) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Adding a setting `max_estimated_execution_time` to separate `max_execution_time` and `max_estimated_execution_time`. [#58402](https://github.com/ClickHouse/ClickHouse/pull/58402) ([Zhang Yifan](https://github.com/zhangyifan27)).
* Provide a hint when an invalid database engine name is used. [#58444](https://github.com/ClickHouse/ClickHouse/pull/58444) ([Bharat Nallan](https://github.com/bharatnc)).
* Add settings for better control of indexes type in Arrow dictionary. Use signed integer type for indexes by default as Arrow recommends. Closes [#57401](https://github.com/ClickHouse/ClickHouse/issues/57401). [#58519](https://github.com/ClickHouse/ClickHouse/pull/58519) ([Kruglov Pavel](https://github.com/Avogar)).
* Implement [#58575](https://github.com/ClickHouse/ClickHouse/issues/58575) Support `CLICKHOUSE_PASSWORD_FILE ` environment variable when running the docker image. [#58583](https://github.com/ClickHouse/ClickHouse/pull/58583) ([Eyal Halpern Shalev](https://github.com/Eyal-Shalev)).
* When executing some queries, which require a lot of streams for reading data, the error `"Paste JOIN requires sorted tables only"` was previously thrown. Now the numbers of streams resize to 1 in that case. [#58608](https://github.com/ClickHouse/ClickHouse/pull/58608) ([Yarik Briukhovetskyi](https://github.com/yariks5s)).
* Better message for INVALID_IDENTIFIER error. [#58703](https://github.com/ClickHouse/ClickHouse/pull/58703) ([Yakov Olkhovskiy](https://github.com/yakov-olkhovskiy)).
* Improved handling of signed numeric literals in normalizeQuery. [#58710](https://github.com/ClickHouse/ClickHouse/pull/58710) ([Salvatore Mesoraca](https://github.com/aiven-sal)).
* Support Point data type for MySQL. [#58721](https://github.com/ClickHouse/ClickHouse/pull/58721) ([Kseniia Sumarokova](https://github.com/kssenii)).
* When comparing a Float32 column and a const string, read the string as Float32 (instead of Float64). [#58724](https://github.com/ClickHouse/ClickHouse/pull/58724) ([Raúl Marín](https://github.com/Algunenano)).
* Improve S3 compatibility, add ECloud EOS storage support. [#58786](https://github.com/ClickHouse/ClickHouse/pull/58786) ([xleoken](https://github.com/xleoken)).
* Allow `KILL QUERY` to cancel backups / restores. This PR also makes running backups and restores visible in `system.processes`. Also, there is a new setting in the server configuration now - `shutdown_wait_backups_and_restores` (default=true) which makes the server either wait on shutdown for all running backups and restores to finish or just cancel them. [#58804](https://github.com/ClickHouse/ClickHouse/pull/58804) ([Vitaly Baranov](https://github.com/vitlibar)).
* Avro format to support ZSTD codec. Closes [#58735](https://github.com/ClickHouse/ClickHouse/issues/58735). [#58805](https://github.com/ClickHouse/ClickHouse/pull/58805) ([flynn](https://github.com/ucasfl)).
* MySQL interface gained support for `net_write_timeout` and `net_read_timeout` settings. `net_write_timeout` is translated into the native `send_timeout` ClickHouse setting and, similarly, `net_read_timeout` into `receive_timeout`. Fixed an issue where it was possible to set MySQL `sql_select_limit` setting only if the entire statement was in upper case. [#58835](https://github.com/ClickHouse/ClickHouse/pull/58835) ([Serge Klochkov](https://github.com/slvrtrn)).
* A better exception message while conflict of creating dictionary and table with the same name. [#58841](https://github.com/ClickHouse/ClickHouse/pull/58841) ([Yarik Briukhovetskyi](https://github.com/yariks5s)).
* Make sure that for custom (created from SQL) disks ether `filesystem_caches_path` (a common directory prefix for all filesystem caches) or `custom_cached_disks_base_directory` (a common directory prefix for only filesystem caches created from custom disks) is specified in server config. `custom_cached_disks_base_directory` has higher priority for custom disks over `filesystem_caches_path`, which is used if the former one is absent. Filesystem cache setting `path` must lie inside that directory, otherwise exception will be thrown preventing disk to be created. This will not affect disks created on an older version and server was upgraded - then the exception will not be thrown to allow the server to successfully start). `custom_cached_disks_base_directory` is added to default server config as `/var/lib/clickhouse/caches/`. Closes [#57825](https://github.com/ClickHouse/ClickHouse/issues/57825). [#58869](https://github.com/ClickHouse/ClickHouse/pull/58869) ([Kseniia Sumarokova](https://github.com/kssenii)).
* MySQL interface gained compatibility with `SHOW WARNINGS`/`SHOW COUNT(*) WARNINGS` queries, though the returned result is always an empty set. [#58929](https://github.com/ClickHouse/ClickHouse/pull/58929) ([Serge Klochkov](https://github.com/slvrtrn)).
* Skip unavailable replicas when executing parallel distributed `INSERT SELECT`. [#58931](https://github.com/ClickHouse/ClickHouse/pull/58931) ([Alexander Tokmakov](https://github.com/tavplubix)).
* Display word-descriptive log level while enabling structured log formatting in json. [#58936](https://github.com/ClickHouse/ClickHouse/pull/58936) ([Tim Liou](https://github.com/wheatdog)).
* MySQL interface gained support for `CAST(x AS SIGNED)` and `CAST(x AS UNSIGNED)` statements via data type aliases: `SIGNED` for Int64, and `UNSIGNED` for UInt64. This improves compatibility with BI tools such as Looker Studio. [#58954](https://github.com/ClickHouse/ClickHouse/pull/58954) ([Serge Klochkov](https://github.com/slvrtrn)).
* Change working directory to the data path in docker container. [#58975](https://github.com/ClickHouse/ClickHouse/pull/58975) ([cangyin](https://github.com/cangyin)).
* Added setting for Azure Blob Storage `azure_max_unexpected_write_error_retries` , can also be set from config under azure section. [#59001](https://github.com/ClickHouse/ClickHouse/pull/59001) ([SmitaRKulkarni](https://github.com/SmitaRKulkarni)).
* Allow server to start with broken data lake table. Closes [#58625](https://github.com/ClickHouse/ClickHouse/issues/58625). [#59080](https://github.com/ClickHouse/ClickHouse/pull/59080) ([Kseniia Sumarokova](https://github.com/kssenii)).
* Allow to ignore schema evolution in the `Iceberg` table engine and read all data using schema specified by the user on table creation or latest schema parsed from metadata on table creation. This is done under a setting `iceberg_engine_ignore_schema_evolution` that is disabled by default. Note that enabling this setting can lead to incorrect result as in case of evolved schema all data files will be read using the same schema. [#59133](https://github.com/ClickHouse/ClickHouse/pull/59133) ([Kruglov Pavel](https://github.com/Avogar)).
* Prohibit mutable operations (`INSERT`/`ALTER`/`OPTIMIZE`/...) on read-only/write-once storages with a proper `TABLE_IS_READ_ONLY` error (to avoid leftovers). Avoid leaving left-overs on write-once disks (`format_version.txt`) on `CREATE`/`ATTACH`. Ignore `DROP` for `ReplicatedMergeTree` (so as for `MergeTree`). Fix iterating over `s3_plain` (`MetadataStorageFromPlainObjectStorage::iterateDirectory`). Note read-only is `web` disk, and write-once is `s3_plain`. [#59170](https://github.com/ClickHouse/ClickHouse/pull/59170) ([Azat Khuzhin](https://github.com/azat)).
* Fix bug in the experimental `_block_number` column which could lead to logical error during complex combination of `ALTER`s and `merge`s. Fixes [#56202](https://github.com/ClickHouse/ClickHouse/issues/56202). Replaces [#58601](https://github.com/ClickHouse/ClickHouse/issues/58601). [#59295](https://github.com/ClickHouse/ClickHouse/pull/59295) ([alesapin](https://github.com/alesapin)).
* Play UI understands when an exception is returned inside JSON. Adjustment for [#52853](https://github.com/ClickHouse/ClickHouse/issues/52853). [#59303](https://github.com/ClickHouse/ClickHouse/pull/59303) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* `/binary` HTTP handler allows to specify user, host, and optionally, password in the query string. [#59311](https://github.com/ClickHouse/ClickHouse/pull/59311) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Support backups for compressed in-memory tables. This closes [#57893](https://github.com/ClickHouse/ClickHouse/issues/57893). [#59315](https://github.com/ClickHouse/ClickHouse/pull/59315) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Support the `FORMAT` clause in `BACKUP` and `RESTORE` queries. [#59338](https://github.com/ClickHouse/ClickHouse/pull/59338) ([Vitaly Baranov](https://github.com/vitlibar)).
* Function `concatWithSeparator` now supports arbitrary argument types (instead of only `String` and `FixedString` arguments). For example, `SELECT concatWithSeparator('.', 'number', 1)` now returns `number.1`. [#59341](https://github.com/ClickHouse/ClickHouse/pull/59341) ([Robert Schulze](https://github.com/rschu1ze)).

#### Build/Testing/Packaging Improvement
* Improve aliases for clickhouse binary (now `ch`/`clickhouse` is `clickhouse-local` or `clickhouse` depends on the arguments) and add bash completion for new aliases. [#58344](https://github.com/ClickHouse/ClickHouse/pull/58344) ([Azat Khuzhin](https://github.com/azat)).
* Add settings changes check to CI to check that all settings changes are reflected in settings changes history. [#58555](https://github.com/ClickHouse/ClickHouse/pull/58555) ([Kruglov Pavel](https://github.com/Avogar)).
* Use tables directly attached from S3 in stateful tests. [#58791](https://github.com/ClickHouse/ClickHouse/pull/58791) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
* Save the whole `fuzzer.log` as an archive instead of the last 100k lines. `tail -n 100000` often removes lines with table definitions. Example:. [#58821](https://github.com/ClickHouse/ClickHouse/pull/58821) ([Dmitry Novik](https://github.com/novikd)).
* Enable Rust on macOS with Aarch64 (this will add fuzzy search in client with skim and the PRQL language, though I don't think that are people who host ClickHouse on darwin, so it is mostly for fuzzy search in client I would say). [#59272](https://github.com/ClickHouse/ClickHouse/pull/59272) ([Azat Khuzhin](https://github.com/azat)).
* Fix aggregation issue in mixed x86_64 and ARM clusters [#59132](https://github.com/ClickHouse/ClickHouse/pull/59132) ([Harry Lee](https://github.com/HarryLeeIBM)).

#### Bug Fix (user-visible misbehavior in an official stable release)

* Add join keys conversion for nested LowCardinality [#51550](https://github.com/ClickHouse/ClickHouse/pull/51550) ([vdimir](https://github.com/vdimir)).
* Flatten only true Nested type if flatten_nested=1, not all Array(Tuple) [#56132](https://github.com/ClickHouse/ClickHouse/pull/56132) ([Kruglov Pavel](https://github.com/Avogar)).
* Fix a bug with projections and the `aggregate_functions_null_for_empty` setting during insertion. [#56944](https://github.com/ClickHouse/ClickHouse/pull/56944) ([Amos Bird](https://github.com/amosbird)).
* Fixed potential exception due to stale profile UUID [#57263](https://github.com/ClickHouse/ClickHouse/pull/57263) ([Vasily Nemkov](https://github.com/Enmk)).
* Fix working with read buffers in StreamingFormatExecutor [#57438](https://github.com/ClickHouse/ClickHouse/pull/57438) ([Kruglov Pavel](https://github.com/Avogar)).
* Ignore MVs with dropped target table during pushing to views [#57520](https://github.com/ClickHouse/ClickHouse/pull/57520) ([Kruglov Pavel](https://github.com/Avogar)).
* Eliminate possible race between ALTER_METADATA and MERGE_PARTS [#57755](https://github.com/ClickHouse/ClickHouse/pull/57755) ([Azat Khuzhin](https://github.com/azat)).
* Fix the expressions order bug in group by with rollup [#57786](https://github.com/ClickHouse/ClickHouse/pull/57786) ([Chen768959](https://github.com/Chen768959)).
* A fix for the obsolete "zero-copy" replication feature: Fix lost blobs after dropping a replica with broken detached parts [#58333](https://github.com/ClickHouse/ClickHouse/pull/58333) ([Alexander Tokmakov](https://github.com/tavplubix)).
* Allow users to work with symlinks in user_files_path [#58447](https://github.com/ClickHouse/ClickHouse/pull/58447) ([Duc Canh Le](https://github.com/canhld94)).
* Fix a crash when graphite table does not have an agg function [#58453](https://github.com/ClickHouse/ClickHouse/pull/58453) ([Duc Canh Le](https://github.com/canhld94)).
* Delay reading from StorageKafka to allow multiple reads in materialized views [#58477](https://github.com/ClickHouse/ClickHouse/pull/58477) ([János Benjamin Antal](https://github.com/antaljanosbenjamin)).
* Fix a stupid case of intersecting parts [#58482](https://github.com/ClickHouse/ClickHouse/pull/58482) ([Alexander Tokmakov](https://github.com/tavplubix)).
* MergeTreePrefetchedReadPool disable for LIMIT only queries [#58505](https://github.com/ClickHouse/ClickHouse/pull/58505) ([Maksim Kita](https://github.com/kitaisreal)).
* Enable ordinary databases while restoration [#58520](https://github.com/ClickHouse/ClickHouse/pull/58520) ([Jihyuk Bok](https://github.com/tomahawk28)).
* Fix Apache Hive threadpool reading for ORC/Parquet/... [#58537](https://github.com/ClickHouse/ClickHouse/pull/58537) ([sunny](https://github.com/sunny19930321)).
* Hide credentials in `system.backup_log`'s `base_backup_name` column [#58550](https://github.com/ClickHouse/ClickHouse/pull/58550) ([Daniel Pozo Escalona](https://github.com/danipozo)).
* `toStartOfInterval` for milli- microsencods values rounding [#58557](https://github.com/ClickHouse/ClickHouse/pull/58557) ([Yarik Briukhovetskyi](https://github.com/yariks5s)).
* Disable `max_joined_block_rows` in ConcurrentHashJoin [#58595](https://github.com/ClickHouse/ClickHouse/pull/58595) ([vdimir](https://github.com/vdimir)).
* Fix join using nullable in the old analyzer [#58596](https://github.com/ClickHouse/ClickHouse/pull/58596) ([vdimir](https://github.com/vdimir)).
* `makeDateTime64`: Allow non-const fraction argument [#58597](https://github.com/ClickHouse/ClickHouse/pull/58597) ([Robert Schulze](https://github.com/rschu1ze)).
* Fix possible NULL dereference during symbolizing inline frames [#58607](https://github.com/ClickHouse/ClickHouse/pull/58607) ([Azat Khuzhin](https://github.com/azat)).
* Improve isolation of query cache entries under re-created users or role switches [#58611](https://github.com/ClickHouse/ClickHouse/pull/58611) ([Robert Schulze](https://github.com/rschu1ze)).
* Fix broken partition key analysis when doing projection optimization [#58638](https://github.com/ClickHouse/ClickHouse/pull/58638) ([Amos Bird](https://github.com/amosbird)).
* Query cache: Fix per-user quota [#58731](https://github.com/ClickHouse/ClickHouse/pull/58731) ([Robert Schulze](https://github.com/rschu1ze)).
* Fix stream partitioning in parallel window functions [#58739](https://github.com/ClickHouse/ClickHouse/pull/58739) ([Dmitry Novik](https://github.com/novikd)).
* Fix double destroy call on exception throw in addBatchLookupTable8 [#58745](https://github.com/ClickHouse/ClickHouse/pull/58745) ([Raúl Marín](https://github.com/Algunenano)).
* Don't process requests in Keeper during shutdown [#58765](https://github.com/ClickHouse/ClickHouse/pull/58765) ([Antonio Andelic](https://github.com/antonio2368)).
* Fix a null pointer dereference in `SlabsPolygonIndex::find` [#58771](https://github.com/ClickHouse/ClickHouse/pull/58771) ([Yarik Briukhovetskyi](https://github.com/yariks5s)).
* Fix JSONExtract function for LowCardinality(Nullable) columns [#58808](https://github.com/ClickHouse/ClickHouse/pull/58808) ([vdimir](https://github.com/vdimir)).
* A fix for unexpected accumulation of memory usage while creating a huge number of tables by CREATE and DROP. [#58831](https://github.com/ClickHouse/ClickHouse/pull/58831) ([Maksim Kita](https://github.com/kitaisreal)).
* Multiple read file log storage in mv [#58877](https://github.com/ClickHouse/ClickHouse/pull/58877) ([János Benjamin Antal](https://github.com/antaljanosbenjamin)).
* Restriction for the access key id for s3. [#58900](https://github.com/ClickHouse/ClickHouse/pull/58900) ([MikhailBurdukov](https://github.com/MikhailBurdukov)).
* Fix possible crash in clickhouse-local during loading suggestions [#58907](https://github.com/ClickHouse/ClickHouse/pull/58907) ([Kruglov Pavel](https://github.com/Avogar)).
* Fix crash when `indexHint` is used [#58911](https://github.com/ClickHouse/ClickHouse/pull/58911) ([Dmitry Novik](https://github.com/novikd)).
* Fix StorageURL forgetting headers on server restart [#58933](https://github.com/ClickHouse/ClickHouse/pull/58933) ([Michael Kolupaev](https://github.com/al13n321)).
* Analyzer: fix storage replacement with insertion block [#58958](https://github.com/ClickHouse/ClickHouse/pull/58958) ([Yakov Olkhovskiy](https://github.com/yakov-olkhovskiy)).
* Fix seek in ReadBufferFromZipArchive [#58966](https://github.com/ClickHouse/ClickHouse/pull/58966) ([Michael Kolupaev](https://github.com/al13n321)).
* A fix for experimental inverted indices (don't use in production): `DROP INDEX` of inverted index now removes all relevant files from persistence [#59040](https://github.com/ClickHouse/ClickHouse/pull/59040) ([mochi](https://github.com/MochiXu)).
* Fix data race on query_factories_info [#59049](https://github.com/ClickHouse/ClickHouse/pull/59049) ([Kseniia Sumarokova](https://github.com/kssenii)).
* Disable "Too many redirects" error retry [#59099](https://github.com/ClickHouse/ClickHouse/pull/59099) ([skyoct](https://github.com/skyoct)).
* Fix not started database shutdown deadlock [#59137](https://github.com/ClickHouse/ClickHouse/pull/59137) ([Sergei Trifonov](https://github.com/serxa)).
* Fix: LIMIT BY and LIMIT in distributed query [#59153](https://github.com/ClickHouse/ClickHouse/pull/59153) ([Igor Nikonov](https://github.com/devcrafter)).
* Fix crash with nullable timezone for `toString` [#59190](https://github.com/ClickHouse/ClickHouse/pull/59190) ([Yarik Briukhovetskyi](https://github.com/yariks5s)).
* Fix abort in iceberg metadata on bad file paths [#59275](https://github.com/ClickHouse/ClickHouse/pull/59275) ([Kruglov Pavel](https://github.com/Avogar)).
* Fix architecture name in select of Rust target [#59307](https://github.com/ClickHouse/ClickHouse/pull/59307) ([p1rattttt](https://github.com/p1rattttt)).
* Fix a logical error about "not-ready set" for querying from `system.tables` with a subquery in the IN clause. [#59351](https://github.com/ClickHouse/ClickHouse/pull/59351) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).

## [Changelog for 2023](https://clickhouse.com/docs/en/whats-new/changelog/2023)