2020 Changelog

- Treat `INTERVAL '1 hour'` as equivalent to `INTERVAL 1 HOUR`, to be compatible with Postgres and similar. This fixes [#15637](https://github.com/ClickHouse/ClickHouse/issues/15637). [#15978](https://github.com/ClickHouse/ClickHouse/pull/15978) ([flynn](https://github.com/ucasFL)).
- Enable parsing enum values by their numeric ids for CSV, TSV and JSON input formats. [#15685](https://github.com/ClickHouse/ClickHouse/pull/15685) ([vivarum](https://github.com/vivarum)).
- Better read task scheduling for JBOD architecture and `MergeTree` storage. New setting `read_backoff_min_concurrency` which serves as the lower limit to the number of reading threads. [#16423](https://github.com/ClickHouse/ClickHouse/pull/16423) ([Amos Bird](https://github.com/amosbird)).
- Add missing support for `LowCardinality` in `Avro` format. [#16521](https://github.com/ClickHouse/ClickHouse/pull/16521) ([Mike](https://github.com/myrrc)).
- 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`. [#16814](https://github.com/ClickHouse/ClickHouse/pull/16814) ([ianton-ru](https://github.com/ianton-ru)).
- Better diagnostics on parse errors in input data. Provide row number on `Cannot read all data` errors. [#16644](https://github.com/ClickHouse/ClickHouse/pull/16644) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Make the behaviour of `minMap` and `maxMap` more desireable. It will not skip zero values in the result. Fixes [#16087](https://github.com/ClickHouse/ClickHouse/issues/16087). [#16631](https://github.com/ClickHouse/ClickHouse/pull/16631) ([Ildus Kurbangaliev](https://github.com/ildus)).
- Better update of ZooKeeper configuration in runtime. [#16630](https://github.com/ClickHouse/ClickHouse/pull/16630) ([sundyli](https://github.com/sundy-li)).
- Apply SETTINGS clause as early as possible. It allows to modify more settings in the query. This closes [#3178](https://github.com/ClickHouse/ClickHouse/issues/3178). [#16619](https://github.com/ClickHouse/ClickHouse/pull/16619) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Now `event_time_microseconds` field stores in Decimal64, not UInt64. [#16617](https://github.com/ClickHouse/ClickHouse/pull/16617) ([Nikita Mikhaylov](https://github.com/nikitamikhaylov)).
- Now paratmeterized functions can be used in `APPLY` column transformer. [#16589](https://github.com/ClickHouse/ClickHouse/pull/16589) ([Amos Bird](https://github.com/amosbird)).
- Improve scheduling of background task which removes data of dropped tables in `Atomic` databases. `Atomic` databases do not create broken symlink to table data directory if table actually has no data directory. [#16584](https://github.com/ClickHouse/ClickHouse/pull/16584) ([tavplubix](https://github.com/tavplubix)).
- Subqueries in `WITH` section (CTE) can reference previous subqueries in `WITH` section by their name. [#16575](https://github.com/ClickHouse/ClickHouse/pull/16575) ([Amos Bird](https://github.com/amosbird)).
- Add current\_database into `system.query_thread_log`. [#16558](https://github.com/ClickHouse/ClickHouse/pull/16558) ([Azat Khuzhin](https://github.com/azat)).
- Allow to fetch parts that are already committed or outdated in the current instance into the detached directory. It's useful when migrating tables from another cluster and having N to 1 shards mapping. It's also consistent with the current fetchPartition implementation. [#16538](https://github.com/ClickHouse/ClickHouse/pull/16538) ([Amos Bird](https://github.com/amosbird)).
- Multiple improvements for `RabbitMQ`: Fixed bug for [#16263](https://github.com/ClickHouse/ClickHouse/issues/16263). Also minimized event loop lifetime. Added more efficient queues setup. [#16426](https://github.com/ClickHouse/ClickHouse/pull/16426) ([Kseniia Sumarokova](https://github.com/kssenii)).
- Fix debug assertion in `quantileDeterministic` function. In previous version it may also transfer up to two times more data over the network. Although no bug existed. This fixes [#15683](https://github.com/ClickHouse/ClickHouse/issues/15683). [#16410](https://github.com/ClickHouse/ClickHouse/pull/16410) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Add `TablesToDropQueueSize` metric. It's equal to number of dropped tables, that are waiting for background data removal. [#16364](https://github.com/ClickHouse/ClickHouse/pull/16364) ([tavplubix](https://github.com/tavplubix)).
- Better diagnostics when client has dropped connection. In previous versions, `Attempt to read after EOF` and `Broken pipe` exceptions were logged in server. In new version, it's information message `Client has dropped the connection, cancel the query.`. [#16329](https://github.com/ClickHouse/ClickHouse/pull/16329) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Add total\_rows/total\_bytes (from system.tables) support for Set/Join table engines. [#16306](https://github.com/ClickHouse/ClickHouse/pull/16306) ([Azat Khuzhin](https://github.com/azat)).
- Now it's possible to specify `PRIMARY KEY` without `ORDER BY` for MergeTree table engines family. Closes [#15591](https://github.com/ClickHouse/ClickHouse/issues/15591). [#16284](https://github.com/ClickHouse/ClickHouse/pull/16284) ([alesapin](https://github.com/alesapin)).
- If there is no tmp folder in the system (chroot, misconfigutation etc) `clickhouse-local` will create temporary subfolder in the current directory. [#16280](https://github.com/ClickHouse/ClickHouse/pull/16280) ([filimonov](https://github.com/filimonov)).
- Add support for nested data types (like named tuple) as sub-types. Fixes [#15587](https://github.com/ClickHouse/ClickHouse/issues/15587). [#16262](https://github.com/ClickHouse/ClickHouse/pull/16262) ([Ivan](https://github.com/abyss7)).
- Support for `database_atomic_wait_for_drop_and_detach_synchronously`/`NO DELAY`/`SYNC` for `DROP DATABASE`. [#16127](https://github.com/ClickHouse/ClickHouse/pull/16127) ([Azat Khuzhin](https://github.com/azat)).
- Add `allow_nondeterministic_optimize_skip_unused_shards` (to allow non deterministic like `rand()` or `dictGet()` in sharding key). [#16105](https://github.com/ClickHouse/ClickHouse/pull/16105) ([Azat Khuzhin](https://github.com/azat)).
- Fix `memory_profiler_step`/`max_untracked_memory` for queries via HTTP (test included). Fix the issue that adjusting this value globally in xml config does not help either, since those settings are not applied anyway, only default (4MB) value is [used](https://github.com/ClickHouse/ClickHouse/blob/17731245336d8c84f75e4c0894c5797ed7732190/src/Common/ThreadStatus.h#L104). Fix `query_id` for the most root ThreadStatus of the http query (by initializing QueryScope after reading query\_id). [#16101](https://github.com/ClickHouse/ClickHouse/pull/16101) ([Azat Khuzhin](https://github.com/azat)).
- Now it's allowed to execute `ALTER ... ON CLUSTER` queries regardless of the `<internal_replication>` setting in cluster config. [#16075](https://github.com/ClickHouse/ClickHouse/pull/16075) ([alesapin](https://github.com/alesapin)).
- Fix rare issue when `clickhouse-client` may abort on exit due to loading of suggestions. This fixes [#16035](https://github.com/ClickHouse/ClickHouse/issues/16035). [#16047](https://github.com/ClickHouse/ClickHouse/pull/16047) ([alexey-milovidov](https://github.com/alexey-milovidov)).
- Add support of `cache` layout for `Redis` dictionaries with complex key. [#15985](https://github.com/ClickHouse/ClickHouse/pull/15985) ([Anton Popov](https://github.com/CurtizJ)).
- Fix query hang (endless loop) in case of misconfiguration (`connections_with_failover_max_tries` set to 0). [#15876](https://github.com/ClickHouse/ClickHouse/pull/15876) ([Azat Khuzhin](https://github.com/azat)).