2023 Changelog

### ClickHouse release 23.5, 2023-06-08. [Presentation](https://presentations.clickhouse.com/2023-release-23.5/), [Video](https://www.youtube.com/watch?v=o8Gj1ClU71M)[​](#235 "Direct link to 235")

#### Upgrade Notes[​](#upgrade-notes "Direct link to Upgrade Notes")

- Compress marks and primary key by default. It significantly reduces the cold query time. Upgrade notes: the support for compressed marks and primary key has been added in version 22.9. If you turned on compressed marks or primary key or installed version 23.5 or newer, which has compressed marks or primary key on by default, you will not be able to downgrade to version 22.8 or earlier. You can also explicitly disable compressed marks or primary keys by specifying the `compress_marks` and `compress_primary_key` settings in the `<merge_tree>` section of the server configuration file. **Upgrade notes:** If you upgrade from versions prior to 22.9, you should either upgrade all replicas at once or disable the compression before upgrade, or upgrade through an intermediate version, where the compressed marks are supported but not enabled by default, such as 23.3. [#42587](https://github.com/ClickHouse/ClickHouse/pull/42587) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
- Make local object storage work consistently with s3 object storage, fix problem with append (closes [#48465](https://github.com/ClickHouse/ClickHouse/issues/48465)), make it configurable as independent storage. The change is backward incompatible because the cache on top of local object storage is not compatible to previous versions. [#48791](https://github.com/ClickHouse/ClickHouse/pull/48791) ([Kseniia Sumarokova](https://github.com/kssenii)).
- The experimental feature "in-memory data parts" is removed. The data format is still supported, but the settings are no-op, and compact or wide parts will be used instead. This closes [#45409](https://github.com/ClickHouse/ClickHouse/issues/45409). [#49429](https://github.com/ClickHouse/ClickHouse/pull/49429) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
- Changed default values of settings `parallelize_output_from_storages` and `input_format_parquet_preserve_order`. This allows ClickHouse to reorder rows when reading from files (e.g. CSV or Parquet), greatly improving performance in many cases. To restore the old behavior of preserving order, use `parallelize_output_from_storages = 0`, `input_format_parquet_preserve_order = 1`. [#49479](https://github.com/ClickHouse/ClickHouse/pull/49479) ([Michael Kolupaev](https://github.com/al13n321)).
- Make projections production-ready. Add the `optimize_use_projections` setting to control whether the projections will be selected for SELECT queries. The setting `allow_experimental_projection_optimization` is obsolete and does nothing. [#49719](https://github.com/ClickHouse/ClickHouse/pull/49719) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
- Mark `joinGet` as non-deterministic (so as `dictGet`). It allows using them in mutations without an extra setting. [#49843](https://github.com/ClickHouse/ClickHouse/pull/49843) ([Azat Khuzhin](https://github.com/azat)).
- Revert the "`groupArray` returns cannot be nullable" change (due to binary compatibility breakage for `groupArray`/`groupArrayLast`/`groupArraySample` over `Nullable` types, which likely will lead to `TOO_LARGE_ARRAY_SIZE` or `CANNOT_READ_ALL_DATA`). [#49971](https://github.com/ClickHouse/ClickHouse/pull/49971) ([Azat Khuzhin](https://github.com/azat)).
- Setting `enable_memory_bound_merging_of_aggregation_results` is enabled by default. If you update from version prior to 22.12, we recommend to set this flag to `false` until update is finished. [#50319](https://github.com/ClickHouse/ClickHouse/pull/50319) ([Nikita Taranov](https://github.com/nickitat)).

#### New Feature[​](#new-feature-7 "Direct link to New Feature")