Altinity Stable for ClickHouse 21.8.8
A few months ago we certified ClickHouse 21.3 as an Altinity Stable release. Since then, we have worked on newer releases and run them in-house. We completed several new features, and even more have been added by community contributors. We were running ClickHouse 21.8 to power our public datasets at Altinity.Cloud instance and testing it in our environments. We have also performed a comprehensive QA of ClickHouse 21.8 to make sure upgrades go smoothly. As of 21.8.8 we are confident in certifying 21.8 as an Altinity Stable release.
This release is a significant upgrade since the previous Altinity Stable release. It includes 1472 pull requests from 224 contributors. Please look below for the detailed release notes.
Major new features since the previous stable release 21.3
A new release introduces a lot of changes and new functions. The full list is available in the Appendix, so refer to this section for more detail. The following new features are worth mentioning on the front page:
- SQL features:
DISTINCT ON
a subset of columns- Partial support of SQL/JSON standard
- Arrays in dictionaries are now supported
- Arrays and nested data types are now supported for Parquet and Arrow formats
- DateTime64 extended range, Now dates between 1925 to 2283 years are supported. a)
- Security features:
- Disk level encryption
- Kerberos authentication for HTTP protocol a)
- Active Directory groups mapping for LDAP user directory a)
- Replication and Cluster improvements:
- ClickHouse Keeper (experimental) – in-process ZooKeeper replacement
- SYSTEM RESTORE REPLICA – a handy tool that makes life easier in the unfortunate occasion if ZooKeeper metadata is lost a)
- Support for MySQL/PostgreSQL clusters when using mysql/postgresql table functions
- Zero-copy replication for S3 tables (see Altinity blog post for details)
- Parts movement between shards (experimental)
- MergeTree features:
- Projections (experimental)
_partition_id
and_partition_value
virtual columns were added- Deduplication for non-replicated tables. See non_replicated_deduplication_window merge tree setting
- Integrations:
MaterializedPostgreSQL
database engine for replication from PostgreSQL- HDFS disk support (experimental)
- Allow to catch Kafka errors into a separate stream (see the KB article on this)
- Other:
- YAML configuration format as an alternative to XML
As usual with ClickHouse, there are many performance and operational improvements in different server components.
a) - contributed by Altinity developers.
Backward Incompatible Changes
The following changes are backward incompatible and require user attention during an upgrade:
- Users of
LowCardinality(Nullable(...))
can not safely downgrade to versions older than 21.4. Data in tables with columns of those types inserted / merged by 21.8 will be lost after the downgrade. - Values of
UUID
type cannot be compared with integers. For example, instead of writinguuid != 0
typeuuid != '00000000-0000-0000-0000-000000000000'
- The
toStartOfIntervalFunction
will align hour intervals to midnight (in previous versions they were aligned to the start of unix epoch). For example,toStartOfInterval(x, INTERVAL 11 HOUR)
will split every day into three intervals:00:00:00..10:59:59
,11:00:00..21:59:59
and22:00:00..23:59:59
. - It’s not possible to rollback to the older ClickHouse version after executing
ALTER ... ATTACH
query as the old servers would fail to process the new command entryATTACH_PART
in the replicated log. - The behaviour of
remote_url_allow_hosts
has changed. In previous versions the empty section did nothing, in 21.8 it will block access to all external hosts. Remove this section from the configuration files after an upgrade if you experience issues with url() or s3() functions. - If you will downgrade to version before 21.1 clickhouse will not be able to start automatically – you will need to remove the system.*_log tables manually to downgrade
- There is an issue with uniqueState(UUID) in AggregatingMergeTree tables, and can be corrected by replacing
uniqState(uuid)
in MATERIALIZED VIEWs
with uniqState(sipHash64(uuid))
and change data type for already saved data fromAggregateFunction(uniq, UUID)
toAggregateFunction(uniq, UInt64)
. For more information see the following:
Upgrade Notes
There were several changes between versions that may affect the rolling upgrade of big clusters. Upgrading only part of the cluster is not recommended.
- Distributed queries with explicitly defined large sets are now executed differently. Compatibility setting
legacy_column_name_of_tuple_literal
may be enabled during the rolling upgrade of the cluster. Otherwise distributed queries with explicitly defined sets at IN clause may fail during upgrade. ATTACH PART[ITION]
queries may not work during cluster upgrade
Other Important Changes
ClickHouse embedded monitoring has become a bit more aggressive. It now collects several system stats, and stores them in the table system.asynchronious_metric_log
. This can be visible as an increase of background writes, storage usage, etc. To return to the old rate of metrics refresh / flush, adjust those settings in config.xml
:
<asynchronous_metrics_update_period_s>
60
</asynchronous_metrics_update_period_s>
<asynchronous_metric_log>
<flush_interval_milliseconds>
60000
</flush_interval_milliseconds>
</asynchronous_metric_log>
Alternatively, metric_log and asynchronous_metric_log tables can be completely disabled:
<yandex>
<asynchronous_metric_log remove="1"/>
<metric_log remove="1"/>
</yandex>
Some new ClickHouse features are now enabled by default. It may lead to a change in behaviour, so review those carefully and disable features that may affect your system:
async_socket_for_remote
compile_aggregate_expressions
compile_expressions
cross_to_inner_join_rewrite
insert_null_as_default
optimize_skip_unused_shards_rewrite_in
query_plan_enable_optimizations
query_plan_filter_push_down
In the previous releases we recommended disabling optimize_on_insert
. This recommendation stays for 21.8 as well as inserts into Summing
and AggregatingMergeTree
can slow down.
Known issues in 21.8.8
The development team continues to improve the quality of the 21.8 release. The following issues still exist in the 21.8.8 version and may affect ClickHouse operation. Please inspect them carefully to decide if those are applicable to your applications:
system.events for event = 'Merge'
are overstated. ClickHouse incorrectly increments this counter.Timeout exceeded: elapsed 18446744073.709553 seconds
error that might happen in extremely rare cases, presumably due to some bug in kernel.
You may also look into a GitHub issues using a special v21.8-affected label.
ClickHouse Altinity Stable Releases are based on the community versions. For more information on installing ClickHouse from either the Altinity Stable builds or the community builds, see the ClickHouse Altinity Stable Release Build Install Guide.
Please contact us at info@altinity.com if you experience any issues with the upgrade.
Appendix
New functions
- DateTime functions:
dateName
timeZone, timeZoneOf, timeZoneOffset, timezoneOf, toTimezone
- JSON processing functions:
JSON_EXISTS, JSON_QUERY, JSON_VALUE
simpleJSONExtractBool, simpleJSONExtractFloat, simpleJSONExtractInt, simpleJSONExtractRaw, simpleJSONExtractString, simpleJSONExtractUInt, simpleJSONHas
toJSONString
- String functions:
bin/unbin
leftPad, lpad, leftPadUTF8
rightPad, rpad, rightPadUTF8
splitByRegexp
- Array functions:
arrayProduct
bitPositionsToArray
validateNestedArraySizes
- Dictionary:
dictGetChildren
dictGetDescendants
dictGetOrNull
- Aggregate functions
deltaSumTimestamp
intervalLengthSum
lagInFrame/leadInFram
esequenceNextNode
sumCount
uniqTheta
- Geo:
polygonAreaCartesian, polygonAreaSpherical
polygonConvexHullCartesian
polygonPerimeterCartesian, polygonPerimeterSpherical
polygonsDistanceCartesian, polygonsDistanceSpherical
polygonsEqualsCartesian
polygonsIntersectionCartesian, polygonsIntersectionSpherical
polygonsSymDifferenceCartesian, polygonsSymDifferenceSpherical
polygonsUnionCartesian, polygonsUnionSpherical
polygonsWithinCartesian, polygonsWithinSpherical
readWktMultiPolygon, readWktPoint, readWktPolygon, readWktRing
wkt
- Math/Statistics:
quantileBFloat16, quantilesBFloat16
- Type related:
reinterpretAsUInt128
toUInt128, toUInt128OrNull, toUInt128OrZero
- Other:
indexHint
isIPAddressInRange
partitionId
– that corresponds to_partition_id virtual
column added to MergeTree tables
New table functions
dictionary
s3Cluster
– see our blog article that highlights this one
New table engines
ExternalDistributed
– allows to query MySQL or PostgreSQL clustersMaterializedPostgreSQL
New metrics and events
system.asynchronous_metrics
AsynchronousMetricsCalculationTimeSpent
The table has also got a lot of new metrics for a host monitoring rather than ClickHouse.
system.metrics
BrokenDistributedFilesToInsert
MMappedFileBytes
NetworkReceive
NetworkSend
system.events
MMappedFileCacheHits
MMappedFileCacheMisses
MergeTreeDataProjectionWriterBlocks
MergeTreeDataProjectionWriterBlocksAlreadySorted
MergeTreeDataProjectionWriterCompressedBytes
MergeTreeDataProjectionWriterRows
MergeTreeDataProjectionWriterUncompressedBytes
NetworkReceiveBytes
NetworkSendBytes
StorageBufferLayerLockReadersWaitMilliseconds
StorageBufferLayerLockWritersWaitMilliseconds
StorageBufferPassedBytesFlushThreshold
StorageBufferPassedRowsFlushThreshold
StorageBufferPassedTimeFlushThreshold
system.errors
CANNOT_CREATE_FILE
CANNOT_PARSE_YAML
CANNOT_SET_ROUNDING_MODE
CANNOT_SYSCONF
CONCURRENT_ACCESS_NOT_SUPPORTED
DISTRIBUTED_BROKEN_BATCH_FILES
DISTRIBUTED_BROKEN_BATCH_INFO
ILLEGAL_PROJECTION
INCORRECT_PART_TYPE
INVALID_FORMAT_INSERT_QUERY_WITH_DATA
KERBEROS_ERROR
NO_SUCH_PROJECTION_IN_TABLE
POSTGRESQL_CONNECTION_FAILURE
PROJECTION_NOT_USED
TOO_LARGE_DISTRIBUTED_DEPTH
UNKNOWN_SNAPSHOT
New system tables
data_skipping_indices
:- database, table, name, type, expr, granularity
part_moves_between_shards
:- database, table, task_name, task_uuid, create_time, part_name, part_uuid, to_shard, update_time, state, num_tries, last_exception
projection_parts
– same as parts but with extra ‘parent_*’ columnsprojection_parts_columns
– same as parts_columns but with extra ‘parent_*’ columns
New columns in system tables
- clusters
shutdown_count
- dictionaries:
key
– removedkey.names, key.types, found_rate
- distribution_queue:
broken_data_files, broken_data_compressed_bytes
- errors:
last_error_time, last_error_message, last_error_trace, remote
- metric_log:
- multiple columns
- parts_columns:
uuid, min_time, max_time
- processes:
- Settings (Map replaces Settings.Names/Values arrays), ProfileEvents (Map replaces ProfileEvents.Names/Values arrays), current_database
- query_log:
projections, initial_query_start_time, initial_query_start_time_microseconds
, Settings (Map replaces Settings.Names/Values arrays), ProfileEvents (Map replaces ProfileEvents.Names/Values arrays)
- query_thread_log:
initial_query_start_time_microseconds
, Settings (Map replaces Settings.Names/Values arrays), ProfileEvents (Map replaces ProfileEvents.Names/Values arrays)
- stack_trace:
thread_name
- table_engines:
supports_projections
- tables:
- comment
- users
grantees_any, grantees_list, grantees_except
System.merge_tree_settings added/changed
Name | Old value | New value | Description |
---|---|---|---|
max_parts_to_merge_at_once | 100 | Max amount of parts which can be merged at once (0 - disabled). Doesn’t affect OPTIMIZE FINAL query. | |
max_replicated_fetches_network_bandwidth | 0 | The maximum speed of data exchange over the network in bytes per second for replicated fetches. Zero means unlimited. | |
max_replicated_sends_network_bandwidth | 0 | The maximum speed of data exchange over the network in bytes per second for replicated sends. Zero means unlimited. | |
min_bytes_to_rebalance_partition_over_jbod | 0 | Minimal amount of bytes to enable part rebalance over JBOD array (0 - disabled). | |
non_replicated_deduplication_window | 0 | How many last blocks of hashes should be kept on disk (0 - disabled). | |
part_moves_between_shards_delay_seconds | 30 | Time to wait before/after moving parts between shards. | |
part_moves_between_shards_enable | 0 | Experimental/Incomplete feature to move parts between shards. Does not take into account sharding expressions. | |
replicated_fetches_http_connection_timeout | 0 | HTTP connection timeout for part fetch requests. Inherited from default profile http_connection_timeout if not set explicitly. | |
replicated_fetches_http_receive_timeout | 0 | HTTP receive timeout for fetch part requests. Inherited from default profile http_receive_timeout if not set explicitly. | |
replicated_fetches_http_send_timeout | 0 | HTTP send timeout for part fetch requests. Inherited from default profile http_send_timeout if not set explicitly. | |
remote_fs_execute_merges_on_single_replica_time_threshold | 10800 | When greater than zero only a single replica starts the merge immediately when merged part on shared storage and ‘allow_remote_fs_zero_copy_replication’ is enabled. |
system.settings added/changed
Type | Name | Old value | New value | Description |
---|---|---|---|---|
settings | allow_experimental_bigint_types | 0 | 1 | Obsolete setting, does nothing. |
settings | allow_experimental_codecs | 0 | If it is set to true, allow to specify experimental compression codecs (but we don't have those yet and this option does nothing). | |
settings | allow_experimental_database_materialized_postgresql | 0 | Allow to create database with Engine=MaterializedPostgreSQL(…). | |
settings | allow_experimental_funnel_functions | 0 | Enable experimental functions for funnel analysis. | |
settings | allow_experimental_map_type | 0 | 1 | Obsolete setting, does nothing. |
settings | allow_experimental_projection_optimization | 0 | Enable projection optimization when processing SELECT queries | |
settings | async_socket_for_remote | 0 | 1 | Asynchronously read from socket executing remote query |
settings | background_schedule_pool_size | 16 | 128 | Number of threads performing background tasks for replicated tables, dns cache updates. Only has meaning at server startup. |
settings | compile_aggregate_expressions | 1 | Compile aggregate functions to native code. | |
settings | compile_expressions | 0 | 1 | Compile some scalar functions and operators to native code. |
settings | cross_to_inner_join_rewrite | 1 | Use inner join instead of comma/cross join if possible | |
settings | database_replicated_always_detach_permanently | 0 | Execute DETACH TABLE as DETACH TABLE PERMANENTLY if database engine is Replicated | |
settings | distributed_ddl_entry_format_version | 1 | Version of DDL entry to write into ZooKeeper | |
settings | distributed_ddl_output_mode | throw | Format of distributed DDL query result | |
settings | distributed_directory_monitor_split_batch_on_failure | 0 | Should StorageDistributed DirectoryMonitors try to split batch into smaller in case of failures. | |
settings | distributed_push_down_limit | 0 | If 1, LIMIT will be applied on each shard separatelly. Usually you don't need to use it, since this will be done automatically if it is possible, i.e. for simple query SELECT FROM LIMIT. | |
settings | experimental_query_deduplication_send_all_part_uuids | 0 | If false only part UUIDs for currently moving parts are sent. If true all read part UUIDs are sent (useful only for testing). | |
settings | external_storage_max_read_bytes | 0 | Limit maximum number of bytes when table with external engine should flush history data. Now supported only for MySQL table engine, database engine, dictionary and MaterializeMySQL. If equal to 0, this setting is disabled | |
settings | external_storage_max_read_rows | 0 | Limit maximum number of rows when table with external engine should flush history data. Now supported only for MySQL table engine, database engine, dictionary and MaterializeMySQL. If equal to 0, this setting is disabled | |
settings | force_optimize_projection | 0 | If projection optimization is enabled, SELECT queries need to use projection | |
settings | glob_expansion_max_elements | 1000 | Maximum number of allowed addresses (For external storages, table functions, etc). | |
settings | group_by_two_level_threshold_bytes | 100000000 | 50000000 | From what size of the aggregation state in bytes, a two-level aggregation begins to be used. 0 - the threshold is not set. Two-level aggregation is used when at least one of the thresholds is triggered. |
settings | handle_kafka_error_mode | default | Obsolete setting, does nothing. | |
settings | http_max_field_name_size | 1048576 | Maximum length of field name in HTTP header | |
settings | http_max_field_value_size | 1048576 | Maximum length of field value in HTTP header | |
settings | http_max_fields | 1000000 | Maximum number of fields in HTTP header | |
settings | http_max_uri_size | 1048576 | Maximum URI length of HTTP request | |
settings | insert_null_as_default | 1 | Insert DEFAULT values instead of NULL in INSERT SELECT (UNION ALL) | |
settings | legacy_column_name_of_tuple_literal | 0 | List all names of element of large tuple literals in their column names instead of hash. This settings exists only for compatibility reasons. It makes sense to set to 'true', while doing rolling update of cluster from version lower than 21.7 to higher. | |
settings | max_distributed_depth | 5 | Maximum distributed query depth | |
settings | max_replicated_fetches_network_bandwidth_for_server | 0 | The maximum speed of data exchange over the network in bytes per second for replicated fetches. Zero means unlimited. Only has meaning at server startup. | |
settings | max_replicated_sends_network_bandwidth_for_server | 0 | The maximum speed of data exchange over the network in bytes per second for replicated sends. Zero means unlimited. Only has meaning at server startup. | |
settings | min_count_to_compile_aggregate_expression | 3 | The number of identical aggregate expressions before they are JIT-compiled | |
settings | normalize_function_names | 1 | 0 | Normalize function names to their canonical names |
settings | odbc_bridge_connection_pool_size | 16 | Connection pool size for each connection settings string in ODBC bridge. | |
settings | optimize_functions_to_subcolumns | 0 | Transform functions to subcolumns, if possible, to reduce amount of read data. E.g. 'length(arr)' -> 'arr.size0', 'col IS NULL' -> 'col.null' | |
settings | optimize_fuse_sum_count_avg | 0 | Fuse aggregate functions sum(), avg(), count() with identical arguments into one sumCount() call, if the query has at least two different functions | |
settings | optimize_move_to_prewhere_if_final | 0 | If query has FINAL , the optimization move_to_prewhere is not always correct and it is enabled only if both settings optimize_move_to_prewhere and optimize_move_to_prewhere_if_final are turned on |
|
settings | optimize_skip_unused_shards_limit | 1000 | Limit for number of sharding key values, turns off optimize_skip_unused_shards if the limit is reached | |
settings | optimize_skip_unused_shards_rewrite_in | 1 | Rewrite IN in query for remote shards to exclude values that does not belong to the shard (requires optimize_skip_unused_shards) | |
settings | output_format_arrow_low_cardinality_as_dictionary | 0 | Enable output LowCardinality type as Dictionary Arrow type | |
settings | postgresql_connection_pool_size | 16 | Connection pool size for PostgreSQL table engine and database engine. | |
settings | postgresql_connection_pool_wait_timeout | 5000 | Connection pool push/pop timeout on empty pool for PostgreSQL table engine and database engine. By default it will block on empty pool. | |
settings | prefer_column_name_to_alias | 0 | Prefer using column names instead of aliases if possible. | |
settings | prefer_global_in_and_join | 0 | If enabled, all IN/JOIN operators will be rewritten as GLOBAL IN/JOIN. It's useful when the to-be-joined tables are only available on the initiator and we need to always scatter their data on-the-fly during distributed processing with the GLOBAL keyword. It's also useful to reduce the need to access the external sources joining external tables. | |
settings | query_plan_enable_optimizations | 1 | Apply optimizations to query plan | |
settings | query_plan_filter_push_down | 1 | Allow to push down filter by predicate query plan step | |
settings | s3_max_single_read_retries | 4 | The maximum number of retries during single S3 read. | |
settings | sleep_in_send_data | 0 | ||
settings | sleep_in_send_data_ms | 0 | Time to sleep in sending data in TCPHandler | |
settings | sleep_in_send_tables_status | 0 | ||
settings | sleep_in_send_tables_status_ms | 0 | Time to sleep in sending tables status response in TCPHandler | |
settings | use_antlr_parser | 0 |
Also, please refer to the release notes from the development team available at the following URLs:
- 21.4 release notes: https://clickhouse.com/docs/en/whats-new/changelog/#clickhouse-release-21-4
- 21.5 release notes: https://clickhouse.com/docs/en/whats-new/changelog/#clickhouse-release-21-5-2021-05-20
- 21.6 release notes: https://clickhouse.com/docs/en/whats-new/changelog/#clickhouse-release-21-6-2021-06-05
- 21.7 release notes: https://clickhouse.com/docs/en/whats-new/changelog/#clickhouse-release-v21-7-2021-07-09
- 21.8 release notes: https://clickhouse.com/docs/en/whats-new/changelog/#clickhouse-release-v21-8-2021-08-12
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