* Support for the `ALTER TABLE t DELETE WHERE` query for non-replicated MergeTree tables ([#2634](https://github.com/yandex/ClickHouse/pull/2634)).
* Support for arbitrary types for the `uniq*` family of aggregate functions ([#2010](https://github.com/yandex/ClickHouse/issues/2010)).
* Support for arbitrary types in comparison operators ([#2026](https://github.com/yandex/ClickHouse/issues/2026)).
* The `users.xml` file allows setting a subnet mask in the format `10.0.0.1/255.255.255.0`. This is necessary for using masks for IPv6 networks with zeros in the middle ([#2637](https://github.com/yandex/ClickHouse/pull/2637)).
* Added the `arrayDistinct` function ([#2670](https://github.com/yandex/ClickHouse/pull/2670)).
* The SummingMergeTree engine can now work with AggregateFunction type columns ([Constantin S. Pan](https://github.com/yandex/ClickHouse/pull/2566)).
### Improvements:
* Changed the numbering scheme for release versions. Now the first part contains the year of release (A.D., Moscow timezone, minus 2000), the second part contains the number for major changes (increases for most releases), and the third part is the patch version. Releases are still backwards compatible, unless otherwise stated in the changelog.
* Faster conversions of floating-point numbers to a string ([Amos Bird](https://github.com/yandex/ClickHouse/pull/2664)).
* If some rows were skipped during an insert due to parsing errors (this is possible with the `input_allow_errors_num` and `input_allow_errors_ratio` settings enabled), the number of skipped rows is now written to the server log ([Leonardo Cecchi](https://github.com/yandex/ClickHouse/pull/2669)).
### Bug fixes:
* Fixed the TRUNCATE command for temporary tables ([Amos Bird](https://github.com/yandex/ClickHouse/pull/2624)).
* Fixed a rare deadlock in the ZooKeeper client library that occurred when there was a network error while reading the response ([c315200](https://github.com/yandex/ClickHouse/commit/c315200e64b87e44bdf740707fc857d1fdf7e947)).
* Fixed an error during a CAST to Nullable types ([#1322](https://github.com/yandex/ClickHouse/issues/1322)).
* Fixed the incorrect result of the `maxIntersection()` function when the boundaries of intervals coincided ([Michael Furmur](https://github.com/yandex/ClickHouse/pull/2657)).
* Fixed incorrect transformation of the OR expression chain in a function argument ([chenxing-xc](https://github.com/yandex/ClickHouse/pull/2663)).
* Fixed performance degradation for queries containing `IN (subquery)` expressions inside another subquery ([#2571](https://github.com/yandex/ClickHouse/issues/2571)).
* Fixed incompatibility between servers with different versions in distributed queries that use a `CAST` function that isn't in uppercase letters ([fe8c4d6](https://github.com/yandex/ClickHouse/commit/fe8c4d64e434cacd4ceef34faa9005129f2190a5)).
* Added missing quoting of identifiers for queries to an external DBMS ([#2635](https://github.com/yandex/ClickHouse/issues/2635)).
### Backward incompatible changes:
* Converting a string containing the number zero to DateTime does not work. Example: `SELECT toDateTime('0')`. This is also the reason that `DateTime DEFAULT '0'` does not work in tables, as well as `<null_value>0</null_value>` in dictionaries. Solution: replace `0` with `0000-00-00 00:00:00`.
