ClickHouse v21.3 Release Notes
Release Date: 2021-03-12 // about 3 years ago-
Backward Incompatible Change
- π Now it's not allowed to create MergeTree tables in old syntax with table TTL because it's just ignored. Attach of old tables is still possible. #20282 (alesapin).
- Now all case-insensitive function names will be rewritten to their canonical representations. This is needed for projection query routing (the upcoming feature). #20174 (Amos Bird).
- π Fix creation of
TTL
in cases, when its expression is a function and it is the same asORDER BY
key. Now it's allowed to set custom aggregation to primary key columns inTTL
withGROUP BY
. Backward incompatible: For primary key columns, which are not inGROUP BY
and aren't set explicitly now is applied functionany
instead ofmax
, when TTL is expired. Also if you use TTL withWHERE
orGROUP BY
you can see exceptions at merges, while making rolling update. #15450 (Anton Popov).
π New Feature
- Add file engine settings:
engine_file_empty_if_not_exists
andengine_file_truncate_on_insert
. #20620 (M0r64n). - β Add aggregate function
deltaSum
for summing the differences between consecutive rows. #20057 (Russ Frank). - New
event_time_microseconds
column insystem.part_log
table. #20027 (Bharat Nallan). - β Added
timezoneOffset(datetime)
function which will give the offset from UTC in seconds. This close #issue:19850. #19962 (keenwolf). - Add setting
insert_shard_id
to support insert data into specific shard from distributed table. #19961 (flynn). - β‘οΈ Function
reinterpretAs
updated to support big integers. Fixes #19691. #19858 (Maksim Kita). - β Added Server Side Encryption Customer Keys (the
x-amz-server-side-encryption-customer-(key/md5)
header) support in S3 client. See the link. Closes #19428. #19748 (Vladimir Chebotarev). - β Added
implicit_key
option forexecutable
dictionary source. It allows to avoid printing key for every record if records comes in the same order as the input keys. Implements #14527. #19677 (Maksim Kita). - Add quota type
query_selects
andquery_inserts
. #19603 (JackyWoo). - β Add function
extractTextFromHTML
#19600 (zlx19950903), (alexey-milovidov). - Tables with
MergeTree*
engine now have two new table-level settings for query concurrency control. Settingmax_concurrent_queries
limits the number of concurrently executed queries which are related to this table. Settingmin_marks_to_honor_max_concurrent_queries
tells to apply previous setting only if query reads at least this number of marks. #19544 (Amos Bird). - β Added
file
function to read file from user_files directory as a String. This is different from thefile
table function. This implements #issue:18851. #19204 (keenwolf).
Experimental feature
- β Add experimental
Replicated
database engine. It replicates DDL queries across multiple hosts. #16193 (tavplubix). - Introduce experimental support for window functions, enabled with
allow_experimental_window_functions = 1
. This is a preliminary, alpha-quality implementation that is not suitable for production use and will change in backward-incompatible ways in future releases. Please see the documentation for the list of supported features. #20337 (Alexander Kuzmenkov). - β Add the ability to backup/restore metadata files for DiskS3. #18377 (Pavel Kovalenko).
π Performance Improvement
- Hedged requests for remote queries. When setting
use_hedged_requests
enabled (off by default), allow to establish many connections with different replicas for query. New connection is enabled in case existent connection(s) with replica(s) were not established withinhedged_connection_timeout
or no data was received withinreceive_data_timeout
. Query uses the first connection which send non empty progress packet (or data packet, ifallow_changing_replica_until_first_data_packet
); other connections are cancelled. Queries withmax_parallel_replicas > 1
are supported. #19291 (Kruglov Pavel). This allows to significantly reduce tail latencies on very large clusters. - β Added support for
PREWHERE
(and enable the corresponding optimization) when tables have row-level security expressions specified. #19576 (Denis Glazachev). - The setting
distributed_aggregation_memory_efficient
is enabled by default. It will lower memory usage and improve performance of distributed queries. #20599 (alexey-milovidov). - π Improve performance of GROUP BY multiple fixed size keys. #20472 (alexey-milovidov).
- π Improve performance of aggregate functions by more strict aliasing. #19946 (alexey-milovidov).
- π Speed up reading from
Memory
tables in extreme cases (when reading speed is in order of 50 GB/sec) by simplification of pipeline and (consequently) less lock contention in pipeline scheduling. #20468 (alexey-milovidov). - π Partially reimplement HTTP server to make it making less copies of incoming and outgoing data. It gives up to 1.5 performance improvement on inserting long records over HTTP. #19516 (Ivan).
- β Add
compress
setting forMemory
tables. If it's enabled the table will use less RAM. On some machines and datasets it can also work faster on SELECT, but it is not always the case. This closes #20093. Note: there are reasons why Memory tables can work slower than MergeTree: (1) lack of compression (2) static size of blocks (3) lack of indices and prewhere... #20168 (alexey-milovidov). - π Slightly better code in aggregation. #20978 (alexey-milovidov).
- β Add back
intDiv
/modulo
specializations for better performance. This fixes #21293 . The regression was introduced in https://github.com/ClickHouse/ClickHouse/pull/18145 . #21307 (Amos Bird). - Do not squash blocks too much on INSERT SELECT if inserting into Memory table. In previous versions inefficient data representation was created in Memory table after INSERT SELECT. This closes #13052. #20169 (alexey-milovidov).
- π Fix at least one case when DataType parser may have exponential complexity (found by fuzzer). This closes #20096. #20132 (alexey-milovidov).
- Parallelize SELECT with FINAL for single part with level > 0 when
do_not_merge_across_partitions_select_final
setting is 1. #19375 (Kruglov Pavel). - Fill only requested columns when querying
system.parts
andsystem.parts_columns
. Closes #19570. #21035 (Anmol Arora). - Perform algebraic optimizations of arithmetic expressions inside
avg
aggregate function. close #20092. #20183 (flynn).
π Improvement
- π Case-insensitive compression methods for table functions. Also fixed LZMA compression method which was checked in upper case. #21416 (Vladimir Chebotarev).
- β Add two settings to delay or throw error during insertion when there are too many inactive parts. This is useful when server fails to clean up parts quickly enough. #20178 (Amos Bird).
- π Provide better compatibility for mysql clients. 1. mysql jdbc 2. mycli. #21367 (Amos Bird).
- Forbid to drop a column if it's referenced by materialized view. Closes #21164. #21303 (flynn).
- MySQL dictionary source will now retry unexpected connection failures (Lost connection to MySQL server during query) which sometimes happen on SSL/TLS connections. #21237 (Alexander Kazakov).
- π Usability improvement: more consistent
DateTime64
parsing: recognize the case when unix timestamp with subsecond resolution is specified as scaled integer (like1111111111222
instead of1111111111.222
). This closes #13194. #21053 (alexey-milovidov). - Do only merging of sorted blocks on initiator with distributed_group_by_no_merge. #20882 (Azat Khuzhin).
- When loading config for mysql source ClickHouse will now randomize the list of replicas with the same priority to ensure the round-robin logics of picking mysql endpoint. This closes #20629. #20632 (Alexander Kazakov).
- Function 'reinterpretAs(x, Type)' renamed into 'reinterpret(x, Type)'. #20611 (Maksim Kita).
- π Support vhost for RabbitMQ engine #20576. #20596 (Kseniia Sumarokova).
- π Improved serialization for data types combined of Arrays and Tuples. Improved matching enum data types to protobuf enum type. Fixed serialization of the
Map
data type. Omitted values are now set by default. #20506 (Vitaly Baranov). - π Fixed race between execution of distributed DDL tasks and cleanup of DDL queue. Now DDL task cannot be removed from ZooKeeper if there are active workers. Fixes #20016. #20448 (tavplubix).
- π Make FQDN and other DNS related functions work correctly in alpine images. #20336 (filimonov).
- Do not allow early constant folding of explicitly forbidden functions. #20303 (Azat Khuzhin).
- Implicit conversion from integer to Decimal type might succeeded if integer value doe not fit into Decimal type. Now it throws
ARGUMENT_OUT_OF_BOUND
. #20232 (tavplubix). - Lockless
SYSTEM FLUSH DISTRIBUTED
. #20215 (Azat Khuzhin). - Normalize count(constant), sum(1) to count(). This is needed for projection query routing. #20175 (Amos Bird).
- π Support all native integer types in bitmap functions. #20171 (Amos Bird).
- β‘οΈ Updated
CacheDictionary
,ComplexCacheDictionary
,SSDCacheDictionary
,SSDComplexKeyDictionary
to use LRUHashMap as underlying index. #20164 (Maksim Kita). - π§ The setting
access_management
is now configurable on startup by providingCLICKHOUSE_DEFAULT_ACCESS_MANAGEMENT
, defaults to disabled (0
) which was the prior value. #20139 (Marquitos). - π Fix toDateTime64(toDate()/toDateTime()) for DateTime64 - Implement DateTime64 clamping to match DateTime behaviour. #20131 (Azat Khuzhin).
- Quota improvements: SHOW TABLES is now considered as one query in the quota calculations, not two queries. SYSTEM queries now consume quota. Fix calculation of interval's end in quota consumption. #20106 (Vitaly Baranov).
- π Supports
path IN (set)
expressions forsystem.zookeeper
table. #20105 (ε°θ·―). - π Show full details of
MaterializeMySQL
tables insystem.tables
. #20051 (Stig Bakken). - π Fix data race in executable dictionary that was possible only on misuse (when the script returns data ignoring its input). #20045 (alexey-milovidov).
- The value of MYSQL_OPT_RECONNECT option can now be controlled by "opt_reconnect" parameter in the config section of mysql replica. #19998 (Alexander Kazakov).
- If user calls
JSONExtract
function withFloat32
type requested, allow inaccurate conversion to the result type. For example the number0.1
in JSON is double precision and is not representable in Float32, but the user still wants to get it. Previous versions return 0 for non-Nullable type and NULL for Nullable type to indicate that conversion is imprecise. The logic was 100% correct but it was surprising to users and leading to questions. This closes #13962. #19960 (alexey-milovidov). - β Add conversion of block structure for INSERT into Distributed tables if it does not match. #19947 (Azat Khuzhin).
- Improvement for the
system.distributed_ddl_queue
table. Initialize MaxDDLEntryID to the last value after restarting. Before this PR, MaxDDLEntryID will remain zero until a new DDLTask is processed. #19924 (Amos Bird). - π Show
MaterializeMySQL
tables insystem.parts
. #19770 (Stig Bakken). - β Add separate config directive for
Buffer
profile. #19721 (Azat Khuzhin). - π Move conditions that are not related to JOIN to WHERE clause. #18720. #19685 (hexiaoting).
- Add ability to throttle INSERT into Distributed based on amount of pending bytes for async send (
bytes_to_delay_insert
/max_delay_to_insert
andbytes_to_throw_insert
settings forDistributed
engine has been added). #19673 (Azat Khuzhin). - π Fix some rare cases when write errors can be ignored in destructors. #19451 (Azat Khuzhin).
- π¨ Print inline frames in stack traces for fatal errors. #19317 (Ivan).
π Bug Fix
- π Fix redundant reconnects to ZooKeeper and the possibility of two active sessions for a single clickhouse server. Both problems introduced in #14678. #21264 (alesapin).
- π Fix error
Bad cast from type ... to DB::ColumnLowCardinality
while inserting into table withLowCardinality
column fromValues
format. Fixes #21140 #21357 (Nikolai Kochetov). - π Fix a deadlock in
ALTER DELETE
mutations for non replicated MergeTree table engines when the predicate contains the table itself. Fixes #20558. #21477 (alesapin). - π Fix SIGSEGV for distributed queries on failures. #21434 (Azat Khuzhin).
- π Now
ALTER MODIFY COLUMN
queries will correctly affect changes in partition key, skip indices, TTLs, and so on. Fixes #13675. #21334 (alesapin). - π Fix bug with
join_use_nulls
and joiningTOTALS
from subqueries. This closes #19362 and #21137. #21248 (vdimir). - π Fix crash in
EXPLAIN
for query withUNION
. Fixes #20876, #21170. #21246 (flynn). - π Now mutations allowed only for table engines that support them (MergeTree family, Memory, MaterializedView). Other engines will report a more clear error. Fixes #21168. #21183 (alesapin).
- π Fixes #21112. Fixed bug that could cause duplicates with insert query (if one of the callbacks came a little too late). #21138 (Kseniia Sumarokova).
- Fix
input_format_null_as_default
take effective when types are nullable. This fixes #21116 . #21121 (Amos Bird). - π fix bug related to cast Tuple to Map. Closes #21029. #21120 (hexiaoting).
- π Fix the metadata leak when the Replicated*MergeTree with custom (non default) ZooKeeper cluster is dropped. #21119 (fastio).
- π Fix type mismatch issue when using LowCardinality keys in joinGet. This fixes #21114. #21117 (Amos Bird).
- fix default_replica_path and default_replica_name values are useless on Replicated(*)MergeTree engine when the engine needs specify other parameters. #21060 (mxzlxy).
- Out of bound memory access was possible when formatting specifically crafted out of range value of type
DateTime64
. This closes #20494. This closes #20543. #21023 (alexey-milovidov). - Block parallel insertions into storage join. #21009 (vdimir).
- π Fixed behaviour, when
ALTER MODIFY COLUMN
created mutation, that will knowingly fail. #21007 (Anton Popov). - β‘οΈ Closes #9969. Fixed Brotli http compression error, which reproduced for large data sizes, slightly complicated structure and with json output format. Update Brotli to the latest version to include the "fix rare access to uninitialized data in ring-buffer". #20991 (Kseniia Sumarokova).
- π Fix 'Empty task was returned from async task queue' on query cancellation. #20881 (Azat Khuzhin).
- π
USE database;
query did not work when using MySQL 5.7 client to connect to ClickHouse server, it's fixed. Fixes #18926. #20878 (tavplubix). - π Fix usage of
-Distinct
combinator with-State
combinator in aggregate functions. #20866 (Anton Popov). - π Fix subquery with union distinct and limit clause. close #20597. #20610 (flynn).
- π Fixed inconsistent behavior of dictionary in case of queries where we look for absent keys in dictionary. #20578 (Nikita Mikhaylov).
- π Fix the number of threads for scalar subqueries and subqueries for index (after #19007 single thread was always used). Fixes #20457, #20512. #20550 (Nikolai Kochetov).
- π Fix crash which could happen if unknown packet was received from remove query (was introduced in #17868). #20547 (Azat Khuzhin).
- β Add proper checks while parsing directory names for async INSERT (fixes SIGSEGV). #20498 (Azat Khuzhin).
- π Fix function
transform
does not work properly for floating point keys. Closes #20460. #20479 (flynn). - π Fix infinite loop when propagating WITH aliases to subqueries. This fixes #20388. #20476 (Amos Bird).
- π Fix abnormal server termination when http client goes away. #20464 (Azat Khuzhin).
- Fix
LOGICAL_ERROR
forjoin_use_nulls=1
when JOIN contains const from SELECT. #20461 (Azat Khuzhin). - π Check if table function
view
is used in expression list and throw an error. This fixes #20342. #20350 (Amos Bird). - Avoid invalid dereference in RANGE_HASHED() dictionary. #20345 (Azat Khuzhin).
- π Fix null dereference with
join_use_nulls=1
. #20344 (Azat Khuzhin). - π Fix incorrect result of binary operations between two constant decimals of different scale. Fixes #20283. #20339 (Maksim Kita).
- π Fix too often retries of failed background tasks for
ReplicatedMergeTree
table engines family. This could lead to too verbose logging and increased CPU load. Fixes #20203. #20335 (alesapin). - Restrict to
DROP
orRENAME
version column of*CollapsingMergeTree
andReplacingMergeTree
table engines. #20300 (alesapin). - π Fixed the behavior when in case of broken JSON we tried to read the whole file into memory which leads to exception from the allocator. Fixes #19719. #20286 (Nikita Mikhaylov).
- π Fix exception during vertical merge for
MergeTree
table engines family which don't allow to perform vertical merges. Fixes #20259. #20279 (alesapin). - π Fix rare server crash on config reload during the shutdown. Fixes #19689. #20224 (alesapin).
- π Fix CTE when using in INSERT SELECT. This fixes #20187, fixes #20195. #20211 (Amos Bird).
- π Fixes #19314. #20156 (Ivan).
- π fix toMinute function to handle special timezone correctly. #20149 (keenwolf).
- π Fix server crash after query with
if
function withTuple
type of then/else branches result.Tuple
type must containArray
or another complex type. Fixes #18356. #20133 (alesapin). - The
MongoDB
table engine now establishes connection only when it's going to read data.ATTACH TABLE
won't try to connect anymore. #20110 (Vitaly Baranov). - π Bugfix in StorageJoin. #20079 (vdimir).
- π Fix the case when calculating modulo of division of negative number by small divisor, the resulting data type was not large enough to accomodate the negative result. This closes #20052. #20067 (alexey-milovidov).
- β‘οΈ MaterializeMySQL: Fix replication for statements that update several tables. #20066 (HΓ₯vard KvΓ₯len).
- π³ Prevent "Connection refused" in docker during initialization script execution. #20012 (filimonov).
EmbeddedRocksDB
is an experimental storage. Fix the issue with lack of proper type checking. Simplified code. This closes #19967. #19972 (alexey-milovidov).- π Fix a segfault in function
fromModifiedJulianDay
when the argument type isNullable(T)
for any integral types other than Int32. #19959 (PHO). - π BloomFilter index crash fix. Fixes #19757. #19884 (Maksim Kita).
- π Deadlock was possible if system.text_log is enabled. This fixes #19874. #19875 (alexey-milovidov).
- π Fix starting the server with tables having default expressions containing dictGet(). Allow getting return type of dictGet() without loading dictionary. #19805 (Vitaly Baranov).
- π Fix clickhouse-client abort exception while executing only
select
. #19790 (taiyang-li). - π Fix a bug that moving pieces to destination table may failed in case of launching multiple clickhouse-copiers. #19743 (madianjun).
- π Background thread which executes
ON CLUSTER
queries might hang waiting for dropped replicated table to do something. It's fixed. #19684 (yiguolei).
π Build/Testing/Packaging Improvement
- π Allow to build ClickHouse with AVX-2 enabled globally. It gives slight performance benefits on modern CPUs. Not recommended for production and will not be supported as official build for now. #20180 (alexey-milovidov).
- π Fix some of the issues found by Coverity. See #19964. #20010 (alexey-milovidov).
- π Allow to start up with modified binary under gdb. In previous version if you set up breakpoint in gdb before start, server will refuse to start up due to failed integrity check. #21258 (alexey-milovidov).
- β Add a test for different compression methods in Kafka. #21111 (filimonov).
- Fixed port clash from test_storage_kerberized_hdfs test. #19974 (Ilya Yatsishin).
- π³ Print
stdout
andstderr
to log when failed to start docker in integration tests. Before this PR there was a very short error message in this case which didn't help to investigate the problems. #20631 (Vitaly Baranov).