2023 Changelog

- Support parallel replicas with the analyzer. [#50441](https://github.com/ClickHouse/ClickHouse/pull/50441) ([Raúl Marín](https://github.com/Algunenano)).
- Add random sleep before large merges/mutations execution to split load more evenly between replicas in case of zero-copy replication. [#51282](https://github.com/ClickHouse/ClickHouse/pull/51282) ([alesapin](https://github.com/alesapin)).
- Do not replicate `ALTER PARTITION` queries and mutations through `Replicated` database if it has only one shard and the underlying table is `ReplicatedMergeTree`. [#51049](https://github.com/ClickHouse/ClickHouse/pull/51049) ([Alexander Tokmakov](https://github.com/tavplubix)).

#### Improvement[​](#improvement-6 "Direct link to Improvement")

- Relax the thresholds for "too many parts" to be more modern. Return the backpressure during long-running insert queries. [#50856](https://github.com/ClickHouse/ClickHouse/pull/50856) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
- Allow to cast IPv6 to IPv4 address for CIDR ::ffff:0:0/96 (IPv4-mapped addresses). [#49759](https://github.com/ClickHouse/ClickHouse/pull/49759) ([Yakov Olkhovskiy](https://github.com/yakov-olkhovskiy)).
- Update MongoDB protocol to support MongoDB 5.1 version and newer. Support for the versions with the old protocol (<3.6) is preserved. Closes [#45621](https://github.com/ClickHouse/ClickHouse/issues/45621), [#49879](https://github.com/ClickHouse/ClickHouse/issues/49879). [#50061](https://github.com/ClickHouse/ClickHouse/pull/50061) ([Nikolay Degterinsky](https://github.com/evillique)).
- Add setting `input_format_max_bytes_to_read_for_schema_inference` to limit the number of bytes to read in schema inference. Closes [#50577](https://github.com/ClickHouse/ClickHouse/issues/50577). [#50592](https://github.com/ClickHouse/ClickHouse/pull/50592) ([Kruglov Pavel](https://github.com/Avogar)).
- Respect setting `input_format_null_as_default` in schema inference. [#50602](https://github.com/ClickHouse/ClickHouse/pull/50602) ([Kruglov Pavel](https://github.com/Avogar)).
- Allow to skip trailing empty lines in CSV/TSV/CustomSeparated formats via settings `input_format_csv_skip_trailing_empty_lines`, `input_format_tsv_skip_trailing_empty_lines` and `input_format_custom_skip_trailing_empty_lines` (disabled by default). Closes [#49315](https://github.com/ClickHouse/ClickHouse/issues/49315). [#50635](https://github.com/ClickHouse/ClickHouse/pull/50635) ([Kruglov Pavel](https://github.com/Avogar)).
- Functions "toDateOrDefault|OrNull" and "accuateCast[OrDefault|OrNull]" now correctly parse numeric arguments. [#50709](https://github.com/ClickHouse/ClickHouse/pull/50709) ([Dmitry Kardymon](https://github.com/kardymonds)).
- Support CSV with whitespace or `\t` field delimiters, and these delimiters are supported in Spark. [#50712](https://github.com/ClickHouse/ClickHouse/pull/50712) ([KevinyhZou](https://github.com/KevinyhZou)).
- Settings `number_of_mutations_to_delay` and `number_of_mutations_to_throw` are enabled by default now with values 500 and 1000 respectively. [#50726](https://github.com/ClickHouse/ClickHouse/pull/50726) ([Anton Popov](https://github.com/CurtizJ)).
- The dashboard correctly shows missing values. This closes [#50831](https://github.com/ClickHouse/ClickHouse/issues/50831). [#50832](https://github.com/ClickHouse/ClickHouse/pull/50832) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
- Added the possibility to use date and time arguments in the syslog timestamp format in functions `parseDateTimeBestEffort*` and `parseDateTime64BestEffort*`. [#50925](https://github.com/ClickHouse/ClickHouse/pull/50925) ([Victor Krasnov](https://github.com/sirvickr)).
- Command line parameter "--password" in clickhouse-client can now be specified only once. [#50966](https://github.com/ClickHouse/ClickHouse/pull/50966) ([Alexey Gerasimchuck](https://github.com/Demilivor)).
- Use `hash_of_all_files` from `system.parts` to check identity of parts during on-cluster backups. [#50997](https://github.com/ClickHouse/ClickHouse/pull/50997) ([Vitaly Baranov](https://github.com/vitlibar)).
- The system table zookeeper\_connection connected\_time identifies the time when the connection is established (standard format), and session\_uptime\_elapsed\_seconds is added, which labels the duration of the established connection session (in seconds). [#51026](https://github.com/ClickHouse/ClickHouse/pull/51026) ([郭小龙](https://github.com/guoxiaolongzte)).
- Improve the progress bar for file/s3/hdfs/url table functions by using chunk size from source data and using incremental total size counting in each thread. Fix the progress bar for \*Cluster functions. This closes [#47250](https://github.com/ClickHouse/ClickHouse/issues/47250). [#51088](https://github.com/ClickHouse/ClickHouse/pull/51088) ([Kruglov Pavel](https://github.com/Avogar)).
- Add total\_bytes\_to\_read to the Progress packet in TCP protocol for better Progress bar. [#51158](https://github.com/ClickHouse/ClickHouse/pull/51158) ([Kruglov Pavel](https://github.com/Avogar)).
- Better checking of data parts on disks with filesystem cache. [#51164](https://github.com/ClickHouse/ClickHouse/pull/51164) ([Anton Popov](https://github.com/CurtizJ)).
- Fix sometimes not correct current\_elements\_num in fs cache. [#51242](https://github.com/ClickHouse/ClickHouse/pull/51242) ([Kseniia Sumarokova](https://github.com/kssenii)).

#### Build/Testing/Packaging Improvement[​](#buildtestingpackaging-improvement-6 "Direct link to Build/Testing/Packaging Improvement")

- Add embedded keeper-client to standalone keeper binary. [#50964](https://github.com/ClickHouse/ClickHouse/pull/50964) ([pufit](https://github.com/pufit)).
- Actual LZ4 version is used now. [#50621](https://github.com/ClickHouse/ClickHouse/pull/50621) ([Nikita Taranov](https://github.com/nickitat)).
- ClickHouse server will print the list of changed settings on fatal errors. This closes [#51137](https://github.com/ClickHouse/ClickHouse/issues/51137). [#51138](https://github.com/ClickHouse/ClickHouse/pull/51138) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
- Allow building ClickHouse with clang-17. [#51300](https://github.com/ClickHouse/ClickHouse/pull/51300) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
- [SQLancer](https://github.com/sqlancer/sqlancer) check is considered stable as bugs that were triggered by it are fixed. Now failures of SQLancer check will be reported as failed check status. [#51340](https://github.com/ClickHouse/ClickHouse/pull/51340) ([Ilya Yatsishin](https://github.com/qoega)).
- Split huge `RUN` in Dockerfile into smaller conditional. Install the necessary tools on demand in the same `RUN` layer, and remove them after that. Upgrade the OS only once at the beginning. Use a modern way to check the signed repository. Downgrade the base repo to ubuntu:20.04 to address the issues on older docker versions. Upgrade golang version to address golang vulnerabilities. [#51504](https://github.com/ClickHouse/ClickHouse/pull/51504) ([Mikhail f. Shiryaev](https://github.com/Felixoid)).

#### Bug Fix (user-visible misbehavior in an official stable release)[​](#bug-fix-user-visible-misbehavior-in-an-official-stable-release-6 "Direct link to Bug Fix (user-visible misbehavior in an official stable release)")