* Added support for storage of multidimensional arrays and tuples (`Tuple` data type) in tables.
* Added support for usage of table functions in `DESCRIBE` and `INSERT` queries. Added supoort for subqueries in `DESCRIBE`. Examples: `DESC TABLE remote('host', default.hits)`; `DESC TABLE (SELECT 1)`; `INSERT INTO TABLE FUNCTION remote('host', default.hits)`. Support for `INSERT INTO TABLE` syntax in addition to `INSERT INTO`.
* Improvement of timezones support. `DateTime` data type can be annotated with timezone, that is used for parsing and formatting in text formats. Example: `DateTime('Europe/Moscow')`. When specifying timezones in functions for DateTime arguments, the return type will track timezone, and the value will be displayed as expected.
* Added functions `toTimeZone`, `timeDiff`, `toQuarter`, `toRelativeQuarterNum`. Functions `toRelativeHour`/`Minute`/`Second` can take a value of type `Date` as an argument. The name of function `now` has been made case insensitive.
* Added function `toStartOfFifteenMinutes` (Kirill Shvakov).
* Added tool `clickhouse format` for formatting queries.
* Added configuration parameter `format_schema_path` (Marek Vavruša). It is used for specifying schema of `Cap'n'Proto` format. Schema files can be located only in specified directory.
* Added support for config substitutions (`incl` and `conf.d`) for configuration of external dictionaries and models (Pavel Yakunin).
* Added column with documentation for table `system.settings` (Kirill Shvakov).
* Added table `system.parts_columns` with information about column sizes in each data part of `MergeTree` tables.
* Added table `system.models` with information about loaded `CatBoost` machine learning models.
* Added table functions `mysql` and `odbc` along with corresponding table engines `MySQL`, `ODBC` to work with foreign databases. This feature is in beta stage.
* Added possibility to pass an argument of type `AggregateFunction` for `groupArray` aggregate function (so you can create an array of states of some aggregate function).
* Removed restrictions on various combinations of aggregate function combinators. For example, you can use `avgForEachIf` as well as `avgIfForEach` aggregate functions, that have different behaviour.
* Aggregate function combinator `-ForEach` is extended for the case of aggregate functions of multiple arguments.
* Added support for aggregate functions of `Nullable` arguments even for cases when the function returns non `Nullable` result (added with contribution of Silviu Caragea). Examples: `groupArray`, `groupUniqArray`, `topK`.
* Added command line parameter `max_client_network_bandwidth` for `clickhouse-client` (Kirill Shvakov).
* Allowed to work with TEMPORARY tables (CREATE, DROP, INSERT...) for users with `readonly = 2` setting (Kirill Shvakov).
* Added support for using multiple consumers with `Kafka` engine. Extended configuration options for `Kafka` (Marek Vavruša).
* Added functions `intExp2`, `intExp10`.
* Added aggregate function `sumKahan` (computationally stable summation of floating point numbers).
* Added functions to*Number*OrNull, where *Number* is a numeric type.
* Added support for `WITH` clause for `INSERT SELECT` query (by zhang2014).
* Added settings `http_connection_timeout`, `http_send_timeout`, `http_receive_timeout`. In particular, these settings are used for downloading data parts for replication. Changing these settings allows to have more quick failover in the case of overloaded network.
* Added support for `ALTER` query for tables of type `Null` (Anastasiya Tsarkova). Tables of type `Null` are often used with materialized views.
*`reinterpretAsString` function is extended for all data types that are stored contiguously in memory.
* Added option `--silent` for `clickhouse-local` tool. It suppresses printing query execution info in stderr.
* Added support for reading values of type `Date` from text in a format where month and/or day of month is specified in single digit instead of two digits (Amos Bird).
## Performance optimizations:
* Improved performance of `min`, `max`, `any`, `anyLast`, `anyHeavy`, `argMin`, `argMax` aggregate functions in case of String argument.
* Improved performance of `isInfinite`, `isFinite`, `isNaN`, `roundToExp2` functions.
* Improved performance of parsing and formatting values of type `Date` and `DateTime` in text formats.
* Improved performance and precision of parsing floating point numbers.
* Lowered memory usage for `JOIN` in the case when left and right hands have columns with identical names that are not containing in `USING`.
* Improved performance of `varSamp`, `varPop`, `stddevSamp`, `stddevPop`, `covarSamp`, `covarPop`, `corr` aggregate functions in cost of reducing computational stability. Old functions are available under names: `varSampStable`, `varPopStable`, `stddevSampStable`, `stddevPopStable`, `covarSampStable`, `covarPopStable`, `corrStable`.
## Bug fixes:
* Fixed data deduplication after running `DROP PARTITION` query. In previous version dropping a partition and INSERTing the same data again was not working because INSERTed blocks was considered duplicate.
* Fixed bug that may lead to incorrect interpretation of `WHERE` clause for queries `CREATE MATERIALIZED VIEW` with `POPULATE`.
* Fixed bug in using `root_path` parameter in configuration of `zookeeper_servers`.
* Fixed unexpected result of passing `Date` argument to `toStartOfDay`.
* Fixed function `addMonths`, `subtractMonths` and `INTERVAL n MONTH` arithmetic in the case when the result have year less than argument.
* Added missing support of `UUID` data type for `DISTINCT`, `JOIN`, `uniq` aggregate functions and external dictionaries (Ivanov Evgeniy). Support for `UUID` is still incomplete.
* Fixed `SummingMergeTree` behaviour in cases of rows summed to zero.
* Various fixes for `Kafka` engine (Marek Vavruša).
* Fixed incorrect behaviour of `Join` table engine (Amos Bird).
* Fixed wrong behaviour of allocator under FreeBSD and OS X.
*`extractAll` function now support empty matches.
* Fixed error that blocks usage of `libressl` instead of `openssl`.
* Fixed query `CREATE TABLE AS SELECT` from temporary tables.
* Fixed non-atomicity of updating replication queue. This could lead to desync of replicas until server restart.
* Fixed possible overflow in `gcd`, `lcm` and `modulo` (`%` operator) (Maks Skorokhod).
*`-preprocessed` files now created after changing of `umask` (`umask` can be changed in config).
* Fixed bug in background check of parts (`MergeTreePartChecker`) in the case of using custom partition key.
* Fixed parsing of tuples (values of `Tuple` data type) in text formats.
* Improved error messages about incompatible types passed to `multiIf`, `array` and some other functions.
* Support for `Nullable` types is completely reworked. Fixed bugs, that may lead to server crash. Fixed almost all other bugs related to NULL support: incorrect type conversions in INSERT SELECT, unsufficient support for Nullable in HAVING and PREWHERE, `join_use_nulls` mode, Nullable types as arguments of OR operator, etc.
* Fixed various bugs related to internal semantics of data types. Examples: unnecessary summing fields of `Enum` type in `SummingMergeTree`; alignment of `Enum` types in Pretty formats, etc.
* More strict checks for allowed combinations of composite columns - fixed several bugs, that could lead to server crash.
* Fixed overflow when specifying very large parameter for `FixedString` data type.
* Fixed bug in aggregate function `topK` in generic case.
* Added missing check for equality of array sizes in arguments of n-ary variants of aggregate functions with `-Array` combinator.
* Fixed `--pager` option for `clickhouse-client` (by ks1322).
* Fixed precision of `exp10` function.
* Fixed behavior of `visitParamExtract` function for better compliance with documentation.
* Fixed crash when specifying incorrect data types.
* Fixed behavior of `DISTINCT` in the case when all columns are constants.
* Fixed query formatting in the case of using `tupleElement` function with complex constant expression as tuple element index.
* Fixed `Dictionary` table engine for dictionaries of type `range_hashed`.
* Fixed bug that leads to excessive rows in the result of `FULL` and `RIGHT JOIN` (Amos Bird).
* Fixed server crash when creating and removing temporary files in `config.d` directories during config reload.
* Fixed `SYSTEM DROP DNS CACHE` query: the cache was flushed but addresses of cluster nodes was not updated.
* Fixed behavior of `MATERIALIZED VIEW` after executing `DETACH TABLE` for the table under the view (Marek Vavruša).
## Build improvements:
* Using `pbuilder` for builds. Build process is almost independent on the environment of build host.
* Single build is used for different OS versions. Packages and binaries have been made compatible with wide range of Linux systems.
* Added `clickhouse-test` package. It can be used to run functional tests.
* Added publishing of source tarball to the repository. It can be used to reproduce build without using GitHub.
* Added limited integration with Travis CI. Due to limits on build time in Travis, only debug build is tested and limited subset of tests are run.
* Added support for `Cap'n'Proto` in default build.
* Changed documentation sources format from `Restructured Text` to `Markdown`.
* Added support for `systemd` (Vladimir Smirnov). It is disabled by default due to incompatibility with some OS images and can be enabled manually.
* For dynamic code generation, `clang` and `lld` are embedded into the `clickhouse` binary. They can also be invoked as `clickhouse clang` and `clickhouse lld`.
* Removed usage of GNU extensions from the code. Enabled `-Wextra` option. When building with `clang`, `libc++` is used instead of `libstdc++`.
* Extracted `clickhouse_parsers` and `clickhouse_common_io` libraries to speed up builds of various tools.
* Marks format for tables of type `Log`, that contain `Nullable` columns, was changed in backward incompatible way. If you have these tables, you should convert them to `TinyLog` type before staring up new server version. To do that, you should replace `ENGINE = Log` to `ENGINE = TinyLog` in corresponding `.sql` file in `metadata` directory. If your table don't have `Nullable` columns or if type of your table is not `Log`, then no actions required.
* Removed setting `experimental_allow_extended_storage_definition_syntax`. Now this feature is enabled by default.
* To avoid confusion, `runningIncome` function is renamed to `runningDifferenceStartingWithFirstValue`.
* Removed `FROM ARRAY JOIN arr` syntax: when ARRAY JOIN is specified directly after FROM with no table (Amos Bird).
* Removed `BlockTabSeparated` format that was used solely for demonstration purposes.
* Changed serialization format of intermediate states of `varSamp`, `varPop`, `stddevSamp`, `stddevPop`, `covarSamp`, `covarPop`, `corr` aggregate functions. If you have stored states of these aggregate functions in tables (using AggregateFunction data type or materialized views with corresponding States), please write a message to clickhouse-feedback@yandex-team.com.
## Please note when upgrading:
* When doing rolling update on cluster, when some of replicas run old version of ClickHouse and some of replicas run new version, replication is temporarily stopped and messages `unknown parameter 'shard'` will appear in log. Replication will continue after updating all replicas of the cluster.
* If you have different ClickHouse versions on the cluster, you can get wrong results for distributed queries with aggregate functions `varSamp`, `varPop`, `stddevSamp`, `stddevPop`, `covarSamp`, `covarPop`, `corr`. You should update all cluster nodes.
* Fixed bug with possible race condition in replication that could lead to data loss. This issue affects versions 1.1.54310 and 1.1.54318. If you use one of these versions with Replicated tables, the update is strongly recommended. This issue shows in logs in Warning messages like `Part ... from own log doesn't exist.` The issue is relevant even if you don't see these messages in logs.
* The processing logic for Nested columns with names ending in -Map in a SummingMergeTree table was extracted to the sumMap aggregate function. You can now specify such columns explicitly.
* Fixed hangups when synchronously inserting into a Distributed table.
* Fixed nonatomic adding and removing of parts in Replicated tables.
* Data inserted into a materialized view is not subjected to unnecessary deduplication.
* Executing a query to a Distributed table for which the local replica is lagging and remote replicas are unavailable does not result in an error anymore.
* Users don't need access permissions to the `default` database to create temporary tables anymore.
* Fixed crashing when specifying the Array type without arguments.
* Fixed hangups when the disk volume containing server logs is full.
* Fixed an overflow in the `toRelativeWeekNum` function for the first week of the Unix epoch.
## Build improvements:
* Several third-party libraries (notably Poco) were updated and converted to git submodules.
* Added the `pointInPolygon` function for working with coordinates on a coordinate plane.
* Added the `sumMap` aggregate function for calculating the sum of arrays, similar to `SummingMergeTree`.
* Added the `trunc` function. Improved performance of the rounding functions (`round`, `floor`, `ceil`, `roundToExp2`) and corrected the logic of how they work. Changed the logic of the `roundToExp2` function for fractions and negative numbers.
* The ClickHouse executable file is now less dependent on the libc version. The same ClickHouse executable file can run on a wide variety of Linux systems. Note: There is still a dependency when using compiled queries (with the setting `compile = 1`, which is not used by default).
*`SYSTEM` queries for server administration: `SYSTEM RELOAD DICTIONARY`, `SYSTEM RELOAD DICTIONARIES`, `SYSTEM DROP DNS CACHE`, `SYSTEM SHUTDOWN`, `SYSTEM KILL`.
* Added functions for working with arrays: `concat`, `arraySlice`, `arrayPushBack`, `arrayPushFront`, `arrayPopBack`, `arrayPopFront`.
* Added the `root` and `identity` parameters for the ZooKeeper configuration. This allows you to isolate individual users on the same ZooKeeper cluster.
* Added the aggregate functions `groupBitAnd`, `groupBitOr`, and `groupBitXor` (for compatibility, they can also be accessed with the names `BIT_AND`, `BIT_OR`, and `BIT_XOR`).
* Improved the process for deleting old nodes in ZooKeeper. Previously, old nodes sometimes didn't get deleted if there were very frequent inserts, which caused the server to be slow to shut down, among other things.
* Fixed randomization when choosing hosts for the connection to ZooKeeper.
* Fixed the exclusion of lagging replicas in distributed queries if the replica is localhost.
* Fixed an error where a data part in a `ReplicatedMergeTree` table could be broken after running `ALTER MODIFY` on an element in a `Nested` structure.
* You can use `libc++` instead of `libstdc++` for builds on Linux.
* Added instructions for using static code analysis tools: `Coverity`, `clang-tidy`, and `cppcheck`.
## Please note when upgrading:
* There is now a higher default value for the MergeTree setting `max_bytes_to_merge_at_max_space_in_pool` (the maximum total size of data parts to merge, in bytes): it has increased from 100 GiB to 150 GiB. This might result in large merges running after the server upgrade, which could cause an increased load on the disk subsystem. If the free space available on the server is less than twice the total amount of the merges that are running, this will cause all other merges to stop running, including merges of small data parts. As a result, INSERT requests will fail with the message "Merges are processing significantly slower than inserts." Use the `SELECT * FROM system.merges` request to monitor the situation. You can also check the `DiskSpaceReservedForMerge` metric in the `system.metrics` table, or in Graphite. You don't need to do anything to fix this, since the issue will resolve itself once the large merges finish. If you find this unacceptable, you can restore the previous value for the `max_bytes_to_merge_at_max_space_in_pool` setting (to do this, go to the `<merge_tree>` section in config.xml, set `<max_bytes_to_merge_at_max_space_in_pool>107374182400</max_bytes_to_merge_at_max_space_in_pool>` and restart the server).
* You can use an optional WITH clause in a SELECT query. Example query: `WITH 1+1 AS a SELECT a, a*a`
* INSERT can be performed synchronously in a Distributed table: OK is returned only after all the data is saved on all the shards. This is activated by the setting insert_distributed_sync=1.
* Added the UUID data type for working with 16-byte identifiers.
* Added aliases of CHAR, FLOAT and other types for compatibility with the Tableau.
* Added the functions toYYYYMM, toYYYYMMDD, and toYYYYMMDDhhmmss for converting time into numbers.
* You can use IP addresses (together with the hostname) to identify servers for clustered DDL queries.
* Added support for non-constant arguments and negative offsets in the function `substring(str, pos, len).`
* Added the max_size parameter for the `groupArray(max_size)(column)` aggregate function, and optimized its performance.
* Improved error messages for queries with invalid syntax.
* Significantly reduced memory consumption and improved performance when merging large sections of MergeTree data.
* Significantly increased the performance of data merges for the ReplacingMergeTree engine.
* Improved performance for asynchronous inserts from a Distributed table by batching multiple source inserts. To enable this functionality, use the setting distributed_directory_monitor_batch_inserts=1.
## Backward incompatible changes:
* Changed the binary format of aggregate states of `groupArray(array_column)` functions for arrays.
## Complete list of changes:
* Added the `output_format_json_quote_denormals` setting, which enables outputting nan and inf values in JSON format.
* Optimized thread allocation when reading from a Distributed table.
* Settings can be modified in readonly mode if the value doesn't change.
* Added the ability to read fractional granules of the MergeTree engine in order to meet restrictions on the block size specified in the preferred_block_size_bytes setting. The purpose is to reduce the consumption of RAM and increase cache locality when processing queries from tables with large columns.
* Efficient use of indexes that contain expressions like `toStartOfHour(x)` for conditions like `toStartOfHour(x) op сonstexpr.`
* Added new settings for MergeTree engines (the merge_tree section in config.xml):
- replicated_deduplication_window_seconds sets the size of deduplication window in seconds for Replicated tables.
- cleanup_delay_period sets how often to start cleanup to remove outdated data.
- replicated_can_become_leader can prevent a replica from becoming the leader (and assigning merges).
* Accelerated cleanup to remove outdated data from ZooKeeper.
* Multiple improvements and fixes for clustered DDL queries. Of particular interest is the new setting distributed_ddl_task_timeout, which limits the time to wait for a response from the servers in the cluster.
* Improved display of stack traces in the server logs.
* Added the "none" value for the compression method.
* You can use multiple dictionaries_config sections in config.xml.
* It is possible to connect to MySQL through a socket in the file system.
* The `system.parts` table has a new column with information about the size of marks, in bytes.
## Bug fixes:
* Distributed tables using a Merge table now work correctly for a SELECT query with a condition on the _table field.
* Fixed a rare race condition in ReplicatedMergeTree when checking data parts.
* Fixed possible freezing on "leader election" when starting a server.
* The max_replica_delay_for_distributed_queries setting was ignored when using a local replica of the data source. This has been fixed.
* Fixed incorrect behavior of `ALTER TABLE CLEAR COLUMN IN PARTITION` when attempting to clean a non-existing column.
* Fixed an exception in the multiIf function when using empty arrays or strings.
* Fixed excessive memory allocations when deserializing Native format.
* Fixed incorrect auto-update of Trie dictionaries.
* Fixed an exception when running queries with a GROUP BY clause from a Merge table when using SAMPLE.
* Fixed a crash of GROUP BY when using distributed_aggregation_memory_efficient=1.
* Now you can specify the database.table in the right side of IN and JOIN.
* Too many threads were used for parallel aggregation. This has been fixed.
* Fixed how the "if" function works with FixedString arguments.
* SELECT worked incorrectly from a Distributed table for shards with a weight of 0. This has been fixed.
* Crashes no longer occur when running `CREATE VIEW IF EXISTS.`
* Fixed incorrect behavior when input_format_skip_unknown_fields=1 is set and there are negative numbers.
* Fixed an infinite loop in the `dictGetHierarchy()` function if there is some invalid data in the dictionary.
* Fixed `Syntax error: unexpected (...)` errors when running distributed queries with subqueries in an IN or JOIN clause and Merge tables.
* Fixed the incorrect interpretation of a SELECT query from Dictionary tables.
* Fixed the "Cannot mremap" error when using arrays in IN and JOIN clauses with more than 2 billion elements.
* Fixed the failover for dictionaries with MySQL as the source.
## Improved workflow for developing and assembling ClickHouse:
* Builds can be assembled in Arcadia.
* You can use gcc 7 to compile ClickHouse.
* Parallel builds using ccache+distcc are faster now.
