* Logging level can be changed without restarting the server.
* Added the `SHOW CREATE DATABASE` query.
* The `query_id` can be passed to `clickhouse-client` (elBroom).
* New setting: `max_network_bandwidth_for_all_users`.
* Added support for `ALTER TABLE ... PARTITION ... ` for `MATERIALIZED VIEW`.
* Added information about the size of uncompressed data parts in the system table.
* Server-to-server encryption support for distributed tables (`<secure>1</secure>` in the replica config in `<remote_servers>`).
* Configuration of the table level for the `ReplicatedMergeTree` family in order to minimize the amount of data stored in zookeeper: `use_minimalistic_checksums_in_zookeeper = 1`
* Configuration of the `clickhouse-client` prompt. By default, server names are now output to the prompt. The server's display name can be changed and sent in the `X-ClickHouse-Display-Name` HTTP header (Kirill Shvakov).
* Multiple comma-separated `topics` can be specified for the `Kafka` engine (Tobias Adamson).
* When a query is stopped by `KILL QUERY` or `replace_running_query`, the client receives the `Query was cancelled` exception instead of an incomplete response.
## Improvements:
*`ALTER TABLE ... DROP/DETACH PARTITION` queries are run before the replication queue.
*`SELECT ... FINAL` and `OPTIMIZE ... FINAL` can be used even when the table has a single data part.
* A `query_log` table can be recreated on the fly if it was deleted manually (Kirill Shvakov).
* The `lengthUTF8` function runs faster (zhang2014).
* Improved performance of synchronous inserts in `Distributed` tables (`insert_distributed_sync = 1`) when there is a very large number of shards.
* The server accepts the `send_timeout` and `receive_timeout` settings from the client and applies them when connecting to the client (they are applied in reverse order: the server socket's `send_timeout` is set to the `receive_timeout` value received from the client, and vice versa).
* More robust crash recovery for asynchronous insertion into `Distributed` tables.
* The return type of the `countEqual` function changed from `UInt32` to `UInt64` (谢磊).
## Bug fixes:
* Fixed an error with `IN` when the left side of the expression is `Nullable`.
* Correct results are now returned when using tuples with `IN` when some of the tuple components are in the table index.
* The `max_execution_time` limit now works correctly with distributed queries.
* Fixed errors when calculating the size of composite columns in the `system.columns` table.
* Fixed an error when creating a temporary table `CREATE TEMPORARY TABLE IF NOT EXISTS`.
* Fixed errors in `StorageKafka` (#2075)
* Fixed server crashes from invalid arguments of certain aggregate functions.
* Fixed the error that prevented the `DETACH DATABASE` query from stopping background tasks for `ReplicatedMergeTree` tables.
*`Too many parts` no longer appears in aggregated materialized views (#2084).
* Corrected recursive handling of substitutions in the config if a substitution must be followed by another substitution on the same level.
* Corrected the syntax in the metadata file when creating a `VIEW` that uses a query with `UNION ALL`.
*`SummingMergeTree` now works correctly for summation of nested data structures with a composite key.
* Fixed the possibility of a race condition when choosing the leader for `ReplicatedMergeTree` tables.
## Build changes:
* The build supports `ninja` instead of `make` and uses it by default for building releases.
* Renamed packages: `clickhouse-server-base` is now `clickhouse-common-static`; `clickhouse-server-common` is now `clickhouse-server`; `clickhouse-common-dbg` is now `clickhouse-common-static-dbg`. To install, use only `clickhouse-server clickhouse-client`. Packages with the old names will still load in the repositories for backward compatibility.
## Backward-incompatible changes:
* Removed the special interpretation of an IN expression if an array is specified on the left side. Previously, the expression `arr IN (set)` was interpreted as "at least one `arr` element belongs to the `set`". To get the same behavior in the new version, write `arrayExists(x -> x IN (set), arr)`.
* Disabled the incorrect use of the socket option `SO_REUSEPORT`, which was incorrectly enabled by default in the Poco library. Note that on Linux there is no longer any reason to simultaneously specify the addresses `::` and `0.0.0.0` for listen – use just `::`, which allows listening to the connection both over IPv4 and IPv6 (with the default kernel config settings). You can also revert to the behavior from previous versions by specifying `<listen_reuse_port>1</listen_reuse_port>` in the config.
