2020 Changelog

#### Improvement[​](#improvement "Direct link to Improvement")

- Remove empty parts after they were pruned by TTL, mutation, or collapsing merge algorithm. [#16895](https://github.com/ClickHouse/ClickHouse/pull/16895) ([Anton Popov](https://github.com/CurtizJ)).
- Enable compact format of directories for asynchronous sends in Distributed tables: `use_compact_format_in_distributed_parts_names` is set to 1 by default. [#16788](https://github.com/ClickHouse/ClickHouse/pull/16788) ([Azat Khuzhin](https://github.com/azat)).
- Abort multipart upload if no data was written to S3. [#16840](https://github.com/ClickHouse/ClickHouse/pull/16840) ([Pavel Kovalenko](https://github.com/Jokser)).
- Reresolve the IP of the `format_avro_schema_registry_url` in case of errors. [#16985](https://github.com/ClickHouse/ClickHouse/pull/16985) ([filimonov](https://github.com/filimonov)).
- Mask password in data\_path in the system.distribution\_queue. [#16727](https://github.com/ClickHouse/ClickHouse/pull/16727) ([Azat Khuzhin](https://github.com/azat)).
- Throw error when use column transformer replaces non existing column. [#16183](https://github.com/ClickHouse/ClickHouse/pull/16183) ([hexiaoting](https://github.com/hexiaoting)).
- Turn off parallel parsing when there is no enough memory for all threads to work simultaneously. Also there could be exceptions like "Memory limit exceeded" when somebody will try to insert extremely huge rows (> min\_chunk\_bytes\_for\_parallel\_parsing), because each piece to parse has to be independent set of strings (one or more). [#16721](https://github.com/ClickHouse/ClickHouse/pull/16721) ([Nikita Mikhaylov](https://github.com/nikitamikhaylov)).
- Install script should always create subdirs in config folders. This is only relevant for Docker build with custom config. [#16936](https://github.com/ClickHouse/ClickHouse/pull/16936) ([filimonov](https://github.com/filimonov)).
- Correct grammar in error message in JSONEachRow, JSONCompactEachRow, and RegexpRow input formats. [#17205](https://github.com/ClickHouse/ClickHouse/pull/17205) ([nico piderman](https://github.com/sneako)).
- Set default `host` and `port` parameters for `SOURCE(CLICKHOUSE(...))` to current instance and set default `user` value to `'default'`. [#16997](https://github.com/ClickHouse/ClickHouse/pull/16997) ([vdimir](https://github.com/vdimir)).
- Throw an informative error message when doing `ATTACH/DETACH TABLE <DICTIONARY>`. Before this PR, `detach table <dict>` works but leads to an ill-formed in-memory metadata. [#16885](https://github.com/ClickHouse/ClickHouse/pull/16885) ([Amos Bird](https://github.com/amosbird)).
- Add cutToFirstSignificantSubdomainWithWWW(). [#16845](https://github.com/ClickHouse/ClickHouse/pull/16845) ([Azat Khuzhin](https://github.com/azat)).
- Server refused to startup with exception message if wrong config is given (`metric_log`.`collect_interval_milliseconds` is missing). [#16815](https://github.com/ClickHouse/ClickHouse/pull/16815) ([Ivan](https://github.com/abyss7)).
- Better exception message when configuration for distributed DDL is absent. This fixes [#5075](https://github.com/ClickHouse/ClickHouse/issues/5075). [#16769](https://github.com/ClickHouse/ClickHouse/pull/16769) ([Nikita Mikhaylov](https://github.com/nikitamikhaylov)).
- Usability improvement: better suggestions in syntax error message when `CODEC` expression is misplaced in `CREATE TABLE` query. This fixes [#12493](https://github.com/ClickHouse/ClickHouse/issues/12493). [#16768](https://github.com/ClickHouse/ClickHouse/pull/16768) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Remove empty directories for async INSERT at start of Distributed engine. [#16729](https://github.com/ClickHouse/ClickHouse/pull/16729) ([Azat Khuzhin](https://github.com/azat)).
- Workaround for use S3 with nginx server as proxy. Nginx currenty does not accept urls with empty path like `http://domain.com?delete`, but vanilla aws-sdk-cpp produces this kind of urls. This commit uses patched aws-sdk-cpp version, which makes urls with "/" as path in this cases, like `http://domain.com/?delete`. [#16709](https://github.com/ClickHouse/ClickHouse/pull/16709) ([ianton-ru](https://github.com/ianton-ru)).
- Allow `reinterpretAs*` functions to work for integers and floats of the same size. Implements [16640](https://github.com/ClickHouse/ClickHouse/issues/16640). [#16657](https://github.com/ClickHouse/ClickHouse/pull/16657) ([flynn](https://github.com/ucasFL)).
- Now, `<auxiliary_zookeepers>` configuration can be changed in `config.xml` and reloaded without server startup. [#16627](https://github.com/ClickHouse/ClickHouse/pull/16627) ([Amos Bird](https://github.com/amosbird)).
- Support SNI in https connections to remote resources. This will allow to connect to Cloudflare servers that require SNI. This fixes [#10055](https://github.com/ClickHouse/ClickHouse/issues/10055). [#16252](https://github.com/ClickHouse/ClickHouse/pull/16252) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Make it possible to connect to `clickhouse-server` secure endpoint which requires SNI. This is possible when `clickhouse-server` is hosted behind TLS proxy. [#16938](https://github.com/ClickHouse/ClickHouse/pull/16938) ([filimonov](https://github.com/filimonov)).
- Fix possible stack overflow if a loop of materialized views is created. This closes [#15732](https://github.com/ClickHouse/ClickHouse/issues/15732). [#16048](https://github.com/ClickHouse/ClickHouse/pull/16048) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Simplify the implementation of background tasks processing for the MergeTree table engines family. There should be no visible changes for user. [#15983](https://github.com/ClickHouse/ClickHouse/pull/15983) ([alesapin](https://github.com/alesapin)).
- Improvement for MaterializeMySQL (experimental feature). Throw exception about right sync privileges when MySQL sync user has error privileges. [#15977](https://github.com/ClickHouse/ClickHouse/pull/15977) ([TCeason](https://github.com/TCeason)).
- Made `indexOf()` use BloomFilter. [#14977](https://github.com/ClickHouse/ClickHouse/pull/14977) ([achimbab](https://github.com/achimbab)).

#### Performance Improvement[​](#performance-improvement "Direct link to Performance Improvement")