2020 Changelog

#### New Feature[​](#new-feature-11 "Direct link to New Feature")

- Add `Avro` and `AvroConfluent` input/output formats [#8571](https://github.com/ClickHouse/ClickHouse/pull/8571) ([Andrew Onyshchuk](https://github.com/oandrew)) [#8957](https://github.com/ClickHouse/ClickHouse/pull/8957) ([Andrew Onyshchuk](https://github.com/oandrew)) [#8717](https://github.com/ClickHouse/ClickHouse/pull/8717) ([alexey-milovidov](https://github.com/alexey-milovidov))
- Multi-threaded and non-blocking updates of expired keys in `cache` dictionaries (with optional permission to read old ones). [#8303](https://github.com/ClickHouse/ClickHouse/pull/8303) ([Nikita Mikhaylov](https://github.com/nikitamikhaylov))
- Add query `ALTER ... MATERIALIZE TTL`. It runs mutation that forces to remove expired data by TTL and recalculates meta-information about TTL in all parts. [#8775](https://github.com/ClickHouse/ClickHouse/pull/8775) ([Anton Popov](https://github.com/CurtizJ))
- Switch from HashJoin to MergeJoin (on disk) if needed [#9082](https://github.com/ClickHouse/ClickHouse/pull/9082) ([Artem Zuikov](https://github.com/4ertus2))
- Added `MOVE PARTITION` command for `ALTER TABLE` [#4729](https://github.com/ClickHouse/ClickHouse/issues/4729) [#6168](https://github.com/ClickHouse/ClickHouse/pull/6168) ([Guillaume Tassery](https://github.com/YiuRULE))
- Reloading storage configuration from configuration file on the fly. [#8594](https://github.com/ClickHouse/ClickHouse/pull/8594) ([Vladimir Chebotarev](https://github.com/excitoon))
- Allowed to change `storage_policy` to not less rich one. [#8107](https://github.com/ClickHouse/ClickHouse/pull/8107) ([Vladimir Chebotarev](https://github.com/excitoon))
- Added support for globs/wildcards for S3 storage and table function. [#8851](https://github.com/ClickHouse/ClickHouse/pull/8851) ([Vladimir Chebotarev](https://github.com/excitoon))
- Implement `bitAnd`, `bitOr`, `bitXor`, `bitNot` for `FixedString(N)` datatype. [#9091](https://github.com/ClickHouse/ClickHouse/pull/9091) ([Guillaume Tassery](https://github.com/YiuRULE))
- Added function `bitCount`. This fixes [#8702](https://github.com/ClickHouse/ClickHouse/issues/8702). [#8708](https://github.com/ClickHouse/ClickHouse/pull/8708) ([alexey-milovidov](https://github.com/alexey-milovidov)) [#8749](https://github.com/ClickHouse/ClickHouse/pull/8749) ([ikopylov](https://github.com/ikopylov))
- Add `generateRandom` table function to generate random rows with given schema. Allows to populate arbitrary test table with data. [#8994](https://github.com/ClickHouse/ClickHouse/pull/8994) ([Ilya Yatsishin](https://github.com/qoega))
- `JSONEachRowFormat`: support special case when objects enclosed in top-level array. [#8860](https://github.com/ClickHouse/ClickHouse/pull/8860) ([Kruglov Pavel](https://github.com/Avogar))
- Now it's possible to create a column with `DEFAULT` expression which depends on a column with default `ALIAS` expression. [#9489](https://github.com/ClickHouse/ClickHouse/pull/9489) ([alesapin](https://github.com/alesapin))
- Allow to specify `--limit` more than the source data size in `clickhouse-obfuscator`. The data will repeat itself with different random seed. [#9155](https://github.com/ClickHouse/ClickHouse/pull/9155) ([alexey-milovidov](https://github.com/alexey-milovidov))
- Added `groupArraySample` function (similar to `groupArray`) with reservior sampling algorithm. [#8286](https://github.com/ClickHouse/ClickHouse/pull/8286) ([Amos Bird](https://github.com/amosbird))
- Now you can monitor the size of update queue in `cache`/`complex_key_cache` dictionaries via system metrics. [#9413](https://github.com/ClickHouse/ClickHouse/pull/9413) ([Nikita Mikhaylov](https://github.com/nikitamikhaylov))
- Allow to use CRLF as a line separator in CSV output format with setting `output_format_csv_crlf_end_of_line` is set to 1 [#8934](https://github.com/ClickHouse/ClickHouse/pull/8934) [#8935](https://github.com/ClickHouse/ClickHouse/pull/8935) [#8963](https://github.com/ClickHouse/ClickHouse/pull/8963) ([Mikhail Korotov](https://github.com/millb))
- Implement more functions of the [H3](https://github.com/uber/h3) API: `h3GetBaseCell`, `h3HexAreaM2`, `h3IndexesAreNeighbors`, `h3ToChildren`, `h3ToString` and `stringToH3` [#8938](https://github.com/ClickHouse/ClickHouse/pull/8938) ([Nico Mandery](https://github.com/nmandery))
- New setting introduced: `max_parser_depth` to control maximum stack size and allow large complex queries. This fixes [#6681](https://github.com/ClickHouse/ClickHouse/issues/6681) and [#7668](https://github.com/ClickHouse/ClickHouse/issues/7668). [#8647](https://github.com/ClickHouse/ClickHouse/pull/8647) ([Maxim Smirnov](https://github.com/qMBQx8GH))
- Add a setting `force_optimize_skip_unused_shards` setting to throw if skipping of unused shards is not possible [#8805](https://github.com/ClickHouse/ClickHouse/pull/8805) ([Azat Khuzhin](https://github.com/azat))
- Allow to configure multiple disks/volumes for storing data for send in `Distributed` engine [#8756](https://github.com/ClickHouse/ClickHouse/pull/8756) ([Azat Khuzhin](https://github.com/azat))
- Support storage policy (`<tmp_policy>`) for storing temporary data. [#8750](https://github.com/ClickHouse/ClickHouse/pull/8750) ([Azat Khuzhin](https://github.com/azat))
- Added `X-ClickHouse-Exception-Code` HTTP header that is set if exception was thrown before sending data. This implements [#4971](https://github.com/ClickHouse/ClickHouse/issues/4971). [#8786](https://github.com/ClickHouse/ClickHouse/pull/8786) ([Mikhail Korotov](https://github.com/millb))
- Added function `ifNotFinite`. It is just a syntactic sugar: `ifNotFinite(x, y) = isFinite(x) ? x : y`. [#8710](https://github.com/ClickHouse/ClickHouse/pull/8710) ([alexey-milovidov](https://github.com/alexey-milovidov))
- Added `last_successful_update_time` column in `system.dictionaries` table [#9394](https://github.com/ClickHouse/ClickHouse/pull/9394) ([Nikita Mikhaylov](https://github.com/nikitamikhaylov))
- Add `blockSerializedSize` function (size on disk without compression) [#8952](https://github.com/ClickHouse/ClickHouse/pull/8952) ([Azat Khuzhin](https://github.com/azat))
- Add function `moduloOrZero` [#9358](https://github.com/ClickHouse/ClickHouse/pull/9358) ([hcz](https://github.com/hczhcz))
- Added system tables `system.zeros` and `system.zeros_mt` as well as tale functions `zeros()` and `zeros_mt()`. Tables (and table functions) contain single column with name `zero` and type `UInt8`. This column contains zeros. It is needed for test purposes as the fastest method to generate many rows. This fixes [#6604](https://github.com/ClickHouse/ClickHouse/issues/6604) [#9593](https://github.com/ClickHouse/ClickHouse/pull/9593) ([Nikolai Kochetov](https://github.com/KochetovNicolai))

#### Experimental Feature[​](#experimental-feature-7 "Direct link to Experimental Feature")

- Add new compact format of parts in `MergeTree`-family tables in which all columns are stored in one file. It helps to increase performance of small and frequent inserts. The old format (one file per column) is now called wide. Data storing format is controlled by settings `min_bytes_for_wide_part` and `min_rows_for_wide_part`. [#8290](https://github.com/ClickHouse/ClickHouse/pull/8290) ([Anton Popov](https://github.com/CurtizJ))
- Support for S3 storage for `Log`, `TinyLog` and `StripeLog` tables. [#8862](https://github.com/ClickHouse/ClickHouse/pull/8862) ([Pavel Kovalenko](https://github.com/Jokser))

#### Bug Fix[​](#bug-fix-49 "Direct link to Bug Fix")