2019 Changelog

#### Improvements[​](#improvements "Direct link to Improvements")

- Added `max_parts_in_total` setting for MergeTree family of tables (default: 100 000) that prevents unsafe specification of partition key #5166. [#5171](https://github.com/ClickHouse/ClickHouse/pull/5171) ([alexey-milovidov](https://github.com/alexey-milovidov))
- `clickhouse-obfuscator`: derive seed for individual columns by combining initial seed with column name, not column position. This is intended to transform datasets with multiple related tables, so that tables will remain JOINable after transformation. [#5178](https://github.com/ClickHouse/ClickHouse/pull/5178) ([alexey-milovidov](https://github.com/alexey-milovidov))
- Added functions `JSONExtractRaw`, `JSONExtractKeyAndValues`. Renamed functions `jsonExtract<type>` to `JSONExtract<type>`. When something goes wrong these functions return the correspondent values, not `NULL`. Modified function `JSONExtract`, now it gets the return type from its last parameter and does not inject nullables. Implemented fallback to RapidJSON in case AVX2 instructions are not available. Simdjson library updated to a new version. [#5235](https://github.com/ClickHouse/ClickHouse/pull/5235) ([Vitaly Baranov](https://github.com/vitlibar))
- Now `if` and `multiIf` functions do not rely on the condition's `Nullable`, but rely on the branches for sql compatibility. [#5238](https://github.com/ClickHouse/ClickHouse/pull/5238) ([Jian Wu](https://github.com/janplus))
- `In` predicate now generates `Null` result from `Null` input like the `Equal` function. [#5152](https://github.com/ClickHouse/ClickHouse/pull/5152) ([Jian Wu](https://github.com/janplus))
- Check the time limit every (flush\_interval / poll\_timeout) number of rows from Kafka. This allows to break the reading from Kafka consumer more frequently and to check the time limits for the top-level streams [#5249](https://github.com/ClickHouse/ClickHouse/pull/5249) ([Ivan](https://github.com/abyss7))
- Link rdkafka with bundled SASL. It should allow to use SASL SCRAM authentication [#5253](https://github.com/ClickHouse/ClickHouse/pull/5253) ([Ivan](https://github.com/abyss7))
- Batched version of RowRefList for ALL JOINS. [#5267](https://github.com/ClickHouse/ClickHouse/pull/5267) ([Artem Zuikov](https://github.com/4ertus2))
- clickhouse-server: more informative listen error messages. [#5268](https://github.com/ClickHouse/ClickHouse/pull/5268) ([proller](https://github.com/proller))
- Support dictionaries in clickhouse-copier for functions in `<sharding_key>` [#5270](https://github.com/ClickHouse/ClickHouse/pull/5270) ([proller](https://github.com/proller))
- Add new setting `kafka_commit_every_batch` to regulate Kafka committing policy.
  It allows to set commit mode: after every batch of messages is handled, or after the whole block is written to the storage. It's a trade-off between losing some messages or reading them twice in some extreme situations. [#5308](https://github.com/ClickHouse/ClickHouse/pull/5308) ([Ivan](https://github.com/abyss7))
- Make `windowFunnel` support other Unsigned Integer Types. [#5320](https://github.com/ClickHouse/ClickHouse/pull/5320) ([sundyli](https://github.com/sundy-li))
- Allow to shadow virtual column `_table` in Merge engine. [#5325](https://github.com/ClickHouse/ClickHouse/pull/5325) ([Ivan](https://github.com/abyss7))
- Make `sequenceMatch` aggregate functions support other unsigned Integer types [#5339](https://github.com/ClickHouse/ClickHouse/pull/5339) ([sundyli](https://github.com/sundy-li))
- Better error messages if checksum mismatch is most likely caused by hardware failures. [#5355](https://github.com/ClickHouse/ClickHouse/pull/5355) ([alexey-milovidov](https://github.com/alexey-milovidov))
- Check that underlying tables support sampling for `StorageMerge` [#5366](https://github.com/ClickHouse/ClickHouse/pull/5366) ([Ivan](https://github.com/abyss7))
- Сlose MySQL connections after their usage in external dictionaries. It is related to issue #893. [#5395](https://github.com/ClickHouse/ClickHouse/pull/5395) ([Clément Rodriguez](https://github.com/clemrodriguez))
- Improvements of MySQL Wire Protocol. Changed name of format to MySQLWire. Using RAII for calling RSA\_free. Disabling SSL if context cannot be created. [#5419](https://github.com/ClickHouse/ClickHouse/pull/5419) ([Yuriy Baranov](https://github.com/yurriy))
- clickhouse-client: allow to run with unaccessable history file (read-only, no disk space, file is directory, ...). [#5431](https://github.com/ClickHouse/ClickHouse/pull/5431) ([proller](https://github.com/proller))
- Respect query settings in asynchronous INSERTs into Distributed tables. [#4936](https://github.com/ClickHouse/ClickHouse/pull/4936) ([TCeason](https://github.com/TCeason))
- Renamed functions `leastSqr` to `simpleLinearRegression`, `LinearRegression` to `linearRegression`, `LogisticRegression` to `logisticRegression`. [#5391](https://github.com/ClickHouse/ClickHouse/pull/5391) ([Nikolai Kochetov](https://github.com/KochetovNicolai))

#### Performance Improvements[​](#performance-improvements "Direct link to Performance Improvements")

- Parallelize processing of parts of non-replicated MergeTree tables in ALTER MODIFY query. [#4639](https://github.com/ClickHouse/ClickHouse/pull/4639) ([Ivan Kush](https://github.com/IvanKush))
- Optimizations in regular expressions extraction. [#5193](https://github.com/ClickHouse/ClickHouse/pull/5193) [#5191](https://github.com/ClickHouse/ClickHouse/pull/5191) ([Danila Kutenin](https://github.com/danlark1))
- Do not add right join key column to join result if it's used only in join on section. [#5260](https://github.com/ClickHouse/ClickHouse/pull/5260) ([Artem Zuikov](https://github.com/4ertus2))
- Freeze the Kafka buffer after first empty response. It avoids multiple invokations of `ReadBuffer::next()` for empty result in some row-parsing streams. [#5283](https://github.com/ClickHouse/ClickHouse/pull/5283) ([Ivan](https://github.com/abyss7))
- `concat` function optimization for multiple arguments. [#5357](https://github.com/ClickHouse/ClickHouse/pull/5357) ([Danila Kutenin](https://github.com/danlark1))
- Query optimisation. Allow push down IN statement while rewriting commа/cross join into inner one. [#5396](https://github.com/ClickHouse/ClickHouse/pull/5396) ([Artem Zuikov](https://github.com/4ertus2))
- Upgrade our LZ4 implementation with reference one to have faster decompression. [#5070](https://github.com/ClickHouse/ClickHouse/pull/5070) ([Danila Kutenin](https://github.com/danlark1))
- Implemented MSD radix sort (based on kxsort), and partial sorting. [#5129](https://github.com/ClickHouse/ClickHouse/pull/5129) ([Evgenii Pravda](https://github.com/kvinty))

#### Bug Fixes[​](#bug-fixes "Direct link to Bug Fixes")