ClickHouse/CHANGELOG.md

ClickHouse release v22.1 FIXME as compared to v21.12.3.32-stable

Backward Incompatible Change

• Add left, right, leftUTF8, rightUTF8 functions. Fix error in implementation of substringUTF8 function with negative offset (offset from the end of string). The functions left and right were previously implemented in parser. Upgrade notes: distributed queries with left or right functions without aliases may throw exception if cluster contains different versions of clickhouse-server. If you are upgrading your cluster and encounter this error, you should finish upgrading your cluster to ensure all nodes have the same version. Also you can add aliases (AS something) to the columns in your queries to avoid this issue. #33407 (alexey-milovidov).
• • Account for scalar subqueries. With this change, rows read in scalar subqueries are now reported in the query_log. If the scalar subquery is cached (repeated or called for several rows) the rows read are only counted once. This change allows KILLing queries and reporting progress while they are executing scalar subqueries. #32271 (Raúl Marín).
• Change ZooKeeper path for zero-copy marks for shared data. Fix for remove marks in ZooKeeper for renamed parts. #32061 (ianton-ru).

New Feature

• Detect format by file extension in file/hdfs/s3/url table functions and HDFS/S3/URL table engines. #33565 (Kruglov Pavel).
• Add new h3 miscellaneous functions: h3DegsToRads, h3RadsToDegs, h3HexAreaKm2, h3CellAreaM2, h3CellAreaRads2. #33479 (Bharat Nallan).
• Added function arrayLastIndex. #33465 (Maksim Kita).
• Auto detect file extension. Close #30918. #33443 (OnePiece).
• Add MONTHNAME function. #33436 (usurai).
• Added function arrayLast. Closes #33390. #33415 (Maksim Kita).
• Add aggregate functions cramersV, cramersVBiasCorrected, theilsU and contingency. These functions calculate dependency (measure of association) between categorial values. All these functions are using cross-tab (histogram on pairs) for implementation. You can imagine it like a correlation coefficient but for any discrete values (not necessary numbers). #33366 (alexey-milovidov).
• If an invalid setting is defined using the SET query or using the query parameters in the HTTP request, error message will contain suggestions that are similar to the invalid setting string (if any exists). #32946 (Antonio Andelic).
• Add EXPLAIN TABLE OVERRIDE query. #32836 (Stig Bakken).
• Support TABLE OVERRIDE clause for MaterializedPostgreSQL. RFC: #31480. #32749 (Kseniia Sumarokova).
• Implement data schema inference for input formats. Allow to skip structure (or write just auto) in table functions file, url, s3, hdfs and in parameters of clickhouse-local . Allow to skip structure in create query for table engines File, HDFS, S3, URL, Merge, Buffer, Distributed and ReplicatedMergeTree (if we add new replicas). #32455 (Kruglov Pavel).
• Added table function hdfsCluster which allows processing files from HDFS in parallel from many nodes in a specified cluster. #32400 (Zhichang Yu).
• • Add "TABLE OVERRIDE" feature for customizing MaterializedMySQL table schemas. #32325 (Stig Bakken).
• Adding support for disks backed by Azure Blob Storage, in a similar way it has been done for disks backed by AWS S3. Current implementation allows for all the basic disk operations. #31505 (Jakub Kuklis).
• • Automatic cluster discovery via Zoo/Keeper. #31442 (vdimir).
• Implement hive table engine to access apache hive from clickhouse. Related RFC: #29245. #31104 (taiyang-li).
• Create any kind of view with comment. ... #31062 (Vasily Nemkov).
• Start and stop servers when hosts and ports configuration changes. #30549 (Kevin Michel).
• Added an ability to read from all replicas within a shard during distributed query. To enable this, set allow_experimental_parallel_reading_from_replicas=true and max_parallel_replicas to any number. This closes #26748. #29279 (Nikita Mikhaylov).
• add grouping sets function, like GROUP BY grouping sets (a, b, (a, b)). #26869 (taylor12805).
• Implemented sparse serialization. It can reduce usage of disk space and improve performance of some queries for columns, which contain a lot of default (zero) values. It can be enabled by setting ratio_for_sparse_serialization. Sparse serialization will be chosen dynamically for column, if it has ratio of number of default values to number of all values above that threshold. Serialization (default or sparse) will be fixed for every column in part, but may varies between parts. #22535 (Anton Popov).

Performance Improvement

• Avoid exponential backtracking in parser. This closes #20158. #33481 (alexey-milovidov).
• Reduce allocated memory for dictionaries with string attributes. #33466 (Maksim Kita).
• Slight performance improvement of reinterpret function. #32587 (alexey-milovidov).
• Non significant change. In extremely rare cases when data part is lost on every replica, after merging of some data parts, the subsequent queries may skip less amount of partitions during partition pruning. This hardly affects anything. #32220 (Azat Khuzhin).

Improvement

• Implement Materialized view getVirtuals function. Close #11210. #33482 (OnePiece).
• add function decodeURLFormComponent. Close #10298. #33451 (SuperDJY).
• Add config to enable ipv4 or ipv6. This close #33381. #33450 (Wu Xueyang).
• Abuse of untuple function was leading to exponential complexity of query analysis (found by fuzzer). This closes #33297. #33445 (alexey-milovidov).
• Add some building options in system.build_options. #33431 (taiyang-li).
• Make installation script working on FreeBSD. This closes #33384. #33418 (alexey-milovidov).
• clickhouse-local: track memory under --max_memory_usage_in_client option. #33341 (Azat Khuzhin).
• Allow negative intervals in function intervalLengthSum. Their length will be added as well. This closes #33323. #33335 (alexey-milovidov).
• LineAsString can be used as output format. This closes #30919. #33331 (Sergei Trifonov).
• support <secure/> in cluster configuration. Close #33270. #33330 (SuperDJY).
• Pressing Ctrl+C twice will terminate clickhouse-benchmark immediately without waiting for in-flight queries. This closes #32586. #33303 (alexey-milovidov).
• Support moving conditions to PREWHERE (setting optimize_move_to_prewhere) for tables of Merge engine if its all underlying tables supports PREWHERE. #33300 (Anton Popov).
• parseDateTimeBestEffort support Unix Timestamp with Milliseconds. #33276 (Ben).
• Always display resource usage (total CPU usage, total RAM usage and max RAM usage per host) in client. #33271 (alexey-milovidov).
• Allow to cancel formats Arrow / Parquet / ORC which failed to be cancelled it case of big files and setting input_format_allow_seeks as false. Closes #29678. #33238 (Kseniia Sumarokova).
• If storage supports SETTINGS allow to pass them as key value or via config. Add this support for mysql. #33231 (Kseniia Sumarokova).
• Correctly prevent nullable primary keys if necessary. This is for #32780. #33218 (Amos Bird).
• Add retry for Postgres connect in case nothing has been fetched yet. Closes #33199. #33209 (Kseniia Sumarokova).
• Validate config keys for external dictionaries. #33095#issuecomment-1000577517. #33130 (Kseniia Sumarokova).
• Inject git information into clickhouse binary file. So we can get source code revision easily from clickhouse binary file. #33124 (taiyang-li).
• Send profile info in clickhouse-local. Closes #33093. #33097 (Kseniia Sumarokova).
• Improve Bool type serialization and deserialization. #32984 (Kruglov Pavel).
• Short circuit evaluation function throwIf support. Closes #32969. #32973 (Maksim Kita).
• Dictionaries added Date32 date type support. Closes #32913. #32971 (Maksim Kita).
• This only happens in unofficial builds. Fixed segfault when inserting data into compressed Decimal, String, FixedString and Array columns. This closes #32939. #32940 (N. Kolotov).
• More efficient handling of globs for url storage. Closes #32866. #32907 (Kseniia Sumarokova).
• • Do not prepend THREADS_COUNT with -j to avoid additional prepending in subprocesses. #32844 (kreuzerkrieg).
• Support hints for clickhouse-client and clickhouse-local. Closes #32237,. #32841 (凌涛).
• Added support for specifying subquery as SQL user defined function. Example: CREATE FUNCTION test AS () -> (SELECT 1). Closes #30755. #32758 (Maksim Kita).
• Improve gRPC compression support for #28671. #32747 (Vitaly Baranov).
• Flush all In-Memory data parts when WAL is not enabled while shutdown server or detaching table. #32742 (nauta).
• Allow to control connection timeouts for mysql (previously was supported only for dictionary source). Closes #16669. Previously default connect_timeout was rather small, now it is configurable. #32734 (Kseniia Sumarokova).
• Support authSource option for storage MongoDB. Closes #32594. #32702 (Kseniia Sumarokova).
• support Date32 for genarateRandom engine. #32643 (nauta).
• Add settings max_concurrent_select_queries and max_concurrent_insert_queries for control concurrent queries by query kind. Close #3575. #32609 (SuperDJY).
• Events clause support for window view watch query. #32607 (vxider).
• Improve handling nested structures with missing columns while reading protobuf. Follow-up to https://github.com/ClickHouse/ClickHouse/pull/31988. #32531 (Vitaly Baranov).
• Allow empty credentials for mongo engine. Closes #26267. #32460 (Kseniia Sumarokova).
• Disable some optimizations for window functions. Closes #31535. Closes #31620. #32453 (Kseniia Sumarokova).
• Allows to connect to mongodb 5.0. Closes #31483,. #32416 (Kseniia Sumarokova).
• Improve keeper writing performance by optimization the size calculation logic. #32366 (zhanglistar).
• • Ignore parse failure of opentelemetry's traceparent header. #32116 (Frank Chen).
• Enable comparison between Decimal and Float. Closes #22626. #31966 (flynn).
• Optimize single part projection materialization. This closes #31669. #31885 (Amos Bird).
• Added settings command_read_timeout, command_write_timeout for StorageExecutable, StorageExecutablePool, ExecutableDictionary, ExecutablePoolDictionary, ExecutableUserDefinedFunctions. Setting command_read_timeout controls timeout for reading data from command stdout in milliseconds. Setting command_write_timeout timeout for writing data to command stdin in milliseconds. Added settings command_termination_timeout for ExecutableUserDefinedFunction, ExecutableDictionary, StorageExecutable. Added setting execute_direct for ExecutableUserDefinedFunction, by default true. Added setting execute_direct for ExecutableDictionary, ExecutablePoolDictionary, by default false. #30957 (Maksim Kita).
• Now date time conversion functions that generates time before 1970-01-01 00:00:00 will be saturated to zero instead of overflow. #29953 (Amos Bird).

Bug Fix

• Specifically crafted input data for Native format may lead to reading uninitialized memory or crash. This is relevant if clickhouse-server is open for write access to adversary. #33050 (Heena Bansal).
• Fixed Apache Avro Union type index out of boundary issue in Apache Avro binary format. #33022 (Harry Lee).
• Fix null pointer dereference in low cardinality data when deserializing LowCardinality data in the Native format. #33021 (Harry Lee).
• • Clickhouse Keeper handler should remove operation when response sent. #32988 (JackyWoo).
• Quota limit was not reached, but the limit was exceeded. This PR fixes #31174. #31656 (sunny).
• Fixed CASTing from String to IPv4 or IPv6 and back Fixed error message in case of failed conversion. ... #27914 (Vasily Nemkov).
• Fixed a bug which leaded to an exception like Unknown aggregate function nothing during an execution on a remote server. This fixes #16689. #26074 (hexiaoting).

Build/Testing/Packaging Improvement

• Properly separate thrift-cmake from arrow-cmake after https://github.com/ClickHouse/ClickHouse/pull/31104 . cc @taiyang-li. #33661 (Amos Bird).
• Remove editing /etc/hosts from Dockerfile. #33635 (Mikhail f. Shiryaev).
• Add actionlint for workflows and verify workflow files via act --list to check the correct workflow syntax. #33612 (Mikhail f. Shiryaev).
• Restore a lost description checking. #33591 (Mikhail f. Shiryaev).
• During migration from Yandex to github actions we've lost static links to the latest master (doc) It solves issue #33480 partially. #33559 (Mikhail f. Shiryaev).
• Avoid strict checking when ENABLE_AZURE_BLOB_STORAGE = 0. This is another try on behalf of https://github.com/ClickHouse/ClickHouse/pull/33219 , which was reverted likely due to CI issues. #33346 (Amos Bird).
• Don't use particular encoding for diff-strings, it may contain multiple different encodings. #33336 (Mikhail f. Shiryaev).
• Add more tests for the nullable primary key feature. Add more tests with different types and merge tree kinds, plus randomly generated data. #33228 (Amos Bird).
• Avoid strict checking when ENABLE_AZURE_BLOB_STORAGE = 0. https://github.com/ClickHouse/ClickHouse/pull/32948#discussion_r773168611 cc @nikitamikhaylov. #33219 (Amos Bird).
• Add a simple tool to visualize flaky tests in web browser. #33185 (alexey-milovidov).
• Prepare ClickHouse to be built with musl-libc. It is not enabled by default. #33134 (alexey-milovidov).
• Enable hermetic build for shared builds. This is mainly for developers. #32968 (Amos Bird).
• • Rename main to pull_request - Add BuilderDebAarch64 to all workflows - Use docker buildkit, save building cache to docker hub and reuse it - Build x86_64 and arm64 docker images separately, then merge them together to a multi-architecture manifest - Tune many docker images to being multi-architecture - Use the images from the current PR/commit in the following dependent builds - Upgrade mysql client in stateless-tests image - Add functional tests for aarch64 for PR actions (forced green for a while) - Add python typing to some scripts - Add docker buildkit to runners' init script - Add func-tester-aarch64 runners - Use docker login --password-stdin to not expose password on exception. #32911 (Mikhail f. Shiryaev).
• Use all available in container processors for PVS studio check and fast tests. Delete coverage image. #32854 (Mikhail f. Shiryaev).
• • Unify init scripts for every worker runner type - Install pigz in AMI. #32800 (Mikhail f. Shiryaev).
• Fix build issue related to azure blob storage. #32788 (Amos Bird).
• Remove readline support. #32574 (Azat Khuzhin).
• PENDING (Should mention submodule updates and versions). #32484 (Raúl Marín).
• • Create a global ENV per job - Clean CCACHE after a build is over. #32478 (Mikhail f. Shiryaev).
• Terminate build when linker path not found. #32437 (JackyWoo).
• • Add arm64 packages - Stream python logs in realtime with PYTHONUNBUFFERED=1 - Fix building docker images in docker/packager/packager script. #32415 (Mikhail f. Shiryaev).

Bug Fix (user-visible misbehaviour in official stable or prestable release)

• Fix wrong database for JOIN w/o explicit database in distributed queries (Fixes: #10471). #33611 (Azat Khuzhin).
• Fix segfault in Avro that appears after the second insert into file. #33566 (Kruglov Pavel).
• session_id_counter poniter to next slot. #33555 (小路).
• Fix segfault in arrowSchemaToCHHeader if schema contains Dictionary type. Closes #33507. #33529 (Kruglov Pavel).
• Fix parsing incorrect queries with FROM INFILE statement. #33521 (Kruglov Pavel).
• Close issue: #33289 Fix bug when query view with setting offset and limit. #33518 (hexiaoting).
• Fix an exception Block structure mismatch which may happen during insertion into table with default nested LowCardinality column. Fixes #33028. #33504 (Nikolai Kochetov).
• Fix dictionary expressions for RangeHashedDictionary range min and range max attributes when created using DDL. Closes #30809. #33478 (Maksim Kita).
• Fix DROP MaterializedPostgreSQL database. #33468 (Kseniia Sumarokova).
• Fix query cancellation in case of allow_experimental_parallel_reading_from_replicas. #33456 (Azat Khuzhin).
• Fix possible use-after-free for INSERT into MV with concurrent DROP (#32572 significantly reduce the race window, this one should completely eliminate it). #33386 (Azat Khuzhin).
• Do not try to read pass EOF (to workaround a bug in a kernel), this bug can be reproduced on kernels (3.14..5.9), and requires index_granularity_bytes=0 (i.e. turn off adaptive index granularity). #33372 (Azat Khuzhin).
• The commands SYSTEM SUSPEND and SYSTEM ... THREAD FUZZER missed access control. It is fixed. Author: Kevin Michel. #33333 (alexey-milovidov).
• Fix when COMMENT for dictionaries does not appear in system.tables, system.dictionaries. Allow to modify comment for Dictionary engine. Closes #33251. #33261 (Maksim Kita).
• Fix ACL with explicit digit hash in clickhouse-keeper: now the behavior consistent with zookeeper and generated digest is always accepted. #33249 (小路).
• Fix ACLMap num, because acl_to_num will erase. #33246 (小路).
• Add asynchronous inserts (with enabled setting async_insert) to query log. Previously such queries didn't appear in query log. #33239 (Anton Popov).
• Fix WHERE 1=0 for external databases query. Closes #33152. #33214 (Kseniia Sumarokova).
• Fix ddl validation. Fix setting materialized_postgresql_allow_automatic_update. Closes #29535. #33200 (Kseniia Sumarokova).
• Make sure unused replication slots are always removed. Found in #26952,. #33187 (Kseniia Sumarokova).
• Fix MaterializedPostreSQL detach/attach (removing / adding to replication) tables with non-default schema. Found in #29535. #33179 (Kseniia Sumarokova).
• fix incorrect metric: StorageBufferBytes. #33159 (xuyatian).
• Don't allow to write into S3 if path contains globs. #33142 (Kruglov Pavel).
• Fix error Invalid version for SerializationLowCardinality key column in case of reading from LowCardinality column with local_filesystem_read_prefetch or remote_filesystem_read_prefetch enabled. #33046 (Nikolai Kochetov).
• Fix s3 table function reading empty file. Closes #33008. #33037 (Kseniia Sumarokova).
• Remove obsolete code from ConfigProcessor. Yandex specific code is not used anymore. The code contained one minor defect. This defect was reported by Mallik Hassan in #33032. This closes #33032. #33026 (alexey-milovidov).
• Integer overflow to resize the arrays causes heap corrupt. #33024 (varadarajkumar).
• Fix Context leak in case of cancel_http_readonly_queries_on_client_close (i.e. leaking of external tables that had been uploaded the the server and other resources). #32982 (Azat Khuzhin).
• Fix wrong tuple output in CSV format in case of custom csv delimiter. #32981 (Kruglov Pavel).
• Fix hdfs url check that didn't allow using HA namenode address. Bug was introduced in https://github.com/ClickHouse/ClickHouse/pull/31042. #32976 (Kruglov Pavel).
• Fix throwing exception like positional argument out of bounds for non-positional arguments. Closes #31173#event-5789668239. #32961 (Kseniia Sumarokova).
• Fix UB in case of unexpected EOF during filling a set from HTTP query (i.e. if the client interrupted in the middle, i.e. timeout 0.15s curl -Ss -F 's=@t.csv;' 'http://127.0.0.1:8123/?s_structure=key+Int&query=SELECT+dummy+IN+s' and with large enough t.csv). #32955 (Azat Khuzhin).
• Fix a regression in replaceRegexpAll function. The function worked incorrectly when matched substring was empty. This closes #32777. This closes #30245. #32945 (alexey-milovidov).
• Fix ORC stripe reading. #32929 (kreuzerkrieg).
• Close #32487. #32914 (vdimir).
• Fix MV query with multiple chunk result. Fixes #31419. #32862 (Nikolai Kochetov).
• Fixed --echo option is not used by clickhouse-client in batch mode with single query. #32843 (N. Kolotov).
• Fix optimization with lazy seek for async reads from remote fs. Closes #32803. #32835 (Kseniia Sumarokova).
• MergeTree table engine might silently skip some mutations if there are too many running mutations or in case of high memory consumption, it's fixed. Fixes #17882. #32814 (tavplubix).
• Avoid reusing the scalar subquery cache when processing MV blocks. This fixes a bug when the scalar query reference the source table but it means that all subscalar queries in the MV definition will be calculated for each block. #32811 (Raúl Marín).
• Server might fail to start if database with MySQL engine cannot connect to MySQL server, it's fixed. Fixes #14441. #32802 (tavplubix).
• Fix --database option for clickhouse-local. #32797 (Kseniia Sumarokova).
• fix crash when used fuzzBits with multiply same FixedString, Close #32737. #32755 (SuperDJY).
• Fix error Column is not under aggregate function in case of MV with GROUP BY (list of columns) (which is pared as GROUP BY tuple(...)) over Kafka/RabbitMQ. Fixes #32668 and #32744. #32751 (Nikolai Kochetov).
• Fix ALTER TABLE ... MATERIALIZE TTL query with TTL ... DELETE WHERE ... and TTL ... GROUP BY ... modes. #32695 (Anton Popov).
• Fix optimize_read_in_order optimization in case when table engine is Distributed or Merge and its underlying MergeTree tables have monotonous function in prefix of sorting key. #32670 (Anton Popov).
• Fix LOGICAL_ERROR when the target of a materialized view is a JOIN or a SET table. #32669 (Raúl Marín).
• close #32504. #32649 (vdimir).
• Fix surprisingly bad code in function file. #32640 (alexey-milovidov).
• Fix possible exception at RabbitMQ storage startup by delaying channel creation. #32584 (Kseniia Sumarokova).
• Fix table lifetime (i.e. possible use-after-free) in case of parallel DROP TABLE and INSERT. #32572 (Azat Khuzhin).
• Fix sparse_hashed dict performance with sequential keys (wrong hash function). #32536 (Azat Khuzhin).
• Fix async inserts with formats CustomSeparated, Template, Regexp, MsgPack and JSONAsString. Previousely async inserts with these formats didn't read any data. #32530 (Kruglov Pavel).
• fix groupBitmapAnd function on distributed table. #32529 (minhthucdao).
• Fix crash in JoinCommon::removeColumnNullability, close #32458. #32508 (vdimir).
• The Proper handle of the case with apache arrow column duplication. #32507 (Dmitriy Mokhnatkin).
• Fix issue with ambiguous query formatting in distributed queries that led to errors when some table columns were named ALL or DISTINCT. This closes #32391. #32490 (alexey-milovidov).
• Fix failures in queries that are trying to use skipping indices, which are not materialized yet. Fixes #32292 and #30343. #32359 (Anton Popov).
• Fix broken select query when there are more than 2 row policies on same column, begin at second queries on the same session. #31606. #32291 (SuperDJY).
• Fix unix timestamp Millisecond convert to DateTime64, fractional part calc reversed. #32240 (Ben).
• Some replication queue entries might hang for temporary_directories_lifetime (1 day by default) with Directory tmp_merge_<part_name> or Part ... (state Deleting) already exists, but it will be deleted soon or similar error. It's fixed. Fixes #29616. #32201 (tavplubix).
• Fix 'APPLY lambda' parsing which could lead to client/server crash. #32138 (Kruglov Pavel).
• Fix unexpected projection removal when detaching parts. #32067 (Amos Bird).
• Fix base64Encode adding trailing bytes on small strings. #31797 (Kevin Michel).
• Fixed CAST from String to IPv4 or IPv6 and back. Fixed error message in case of failed conversion. #29224 (Dmitry Novik).

NO CL ENTRY

• NO CL ENTRY: 'Revert "Ignore parse failure of opentelemetry header"'. #33594 (Nikita Mikhaylov).
• NO CL ENTRY: 'Added Superwall to adopters list'. #33573 (Justin Hilliard).
• NO CL ENTRY: 'Revert "Better cmake script for azure blob"'. #33319 (Nikita Mikhaylov).
• NO CL ENTRY: 'Improve query performance of system tables'. #33312 (OnePiece).
• NO CL ENTRY: 'fix hang up with command 'drop table system.query_log sync''. #33293 (zhanghuajie).
• NO CL ENTRY: 'rm redundant judge in hashmap iter operation'. #33285 (zhoubintao).
• NO CL ENTRY: 'Optimize MergeTreePartsMover'. #33225 (OnePiece).
• NO CL ENTRY: 'Revert "Grouping sets dev"'. #33186 (alexey-milovidov).
• NO CL ENTRY: 'Fix for example request with settings'. #33143 (Vitaly Artemyev).
• NO CL ENTRY: 'fix AggregateFunctionGroupBitmapData function rb_contains rb_remove'. #33127 (DR).
• NO CL ENTRY: 'Updated Lawrence Berkeley National Lab stats'. #33066 (Michael Smitasin).
• NO CL ENTRY: 'Revert "Dictionaries added Date32 type support"'. #33053 (tavplubix).
• NO CL ENTRY: 'Revert "Fix build issue related to azure blob storage"'. #32845 (alesapin).
• NO CL ENTRY: 'blog post how to enable predictive capabilities in Clickhouse'. #32768 (Tom Risse).
• NO CL ENTRY: 'Revert "Revert "Split long tests into multiple checks""'. #32515 (alesapin).
• NO CL ENTRY: 'Revert "Split long tests into multiple checks"'. #32514 (alesapin).
• NO CL ENTRY: 'Update CHANGELOG.md'. #32472 (Rich Raposa).

NO CL CATEGORY

• • Allow to split GraphiteMergeTree rollup rules for plain/tagged metrics (optional rule_type field). #33494 (Michail Safronov).
• Fix Regular Expression while key path search. #33023 (mreddy017).

New Feature / New Tool

• Tool for collecting diagnostics data. #33175 (Alexander Burmak).

Bug Fix (v21.9.4.35-stable)

• Fix #32964. #32965 (save-my-heart).

Bug Fix (user-visible misbehaviour in official stable or prestable release):

• Fix possible crash (or incorrect result) in case of LowCardinality arguments of window function. Fixes #31114. #31888 (Nikolai Kochetov).

Build/Testing Improvement

• Added integration test for external .NET client (ClickHouse.Client). #23230 (Oleg V. Kozlyuk).

Changelog for 2021