title_wip

#### Performance Improvement[​](#performance-improvement-3 "Direct link to Performance Improvement")

- Implement compression of marks and primary key. Close [#34437](https://github.com/ClickHouse/ClickHouse/issues/34437). [#37693](https://github.com/ClickHouse/ClickHouse/pull/37693) ([zhongyuankai](https://github.com/zhongyuankai)).
- Allow to load marks with threadpool in advance. Regulated by setting `load_marks_asynchronously` (default: 0). [#40821](https://github.com/ClickHouse/ClickHouse/pull/40821) ([Kseniia Sumarokova](https://github.com/kssenii)).
- Virtual filesystem over s3 will use random object names split into multiple path prefixes for better performance on AWS. [#40968](https://github.com/ClickHouse/ClickHouse/pull/40968) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
- Account `max_block_size` value while producing single-level aggregation results. Allows to execute following query plan steps using more threads. [#39138](https://github.com/ClickHouse/ClickHouse/pull/39138) ([Nikita Taranov](https://github.com/nickitat)).
- Software prefetching is used in aggregation to speed up operations with hash tables. Controlled by the setting `enable_software_prefetch_in_aggregation`, enabled by default. [#39304](https://github.com/ClickHouse/ClickHouse/pull/39304) ([Nikita Taranov](https://github.com/nickitat)).
- Better support of `optimize_read_in_order` in case when some of sorting key columns are always constant after applying `WHERE` clause. E.g. query like `SELECT ... FROM table WHERE a = 'x' ORDER BY a, b`, where `table` has storage definition: `MergeTree ORDER BY (a, b)`. [#38715](https://github.com/ClickHouse/ClickHouse/pull/38715) ([Anton Popov](https://github.com/CurtizJ)).
- Filter joined streams for `full_sorting_join` by each other before sorting. [#39418](https://github.com/ClickHouse/ClickHouse/pull/39418) ([Vladimir C](https://github.com/vdimir)).
- LZ4 decompression optimised by skipping empty literals processing. [#40142](https://github.com/ClickHouse/ClickHouse/pull/40142) ([Nikita Taranov](https://github.com/nickitat)).
- Speedup backup process using native `copy` when possible instead of copying through `clickhouse-server` memory. [#40395](https://github.com/ClickHouse/ClickHouse/pull/40395) ([alesapin](https://github.com/alesapin)).
- Do not obtain storage snapshot for each INSERT block (slightly improves performance). [#40638](https://github.com/ClickHouse/ClickHouse/pull/40638) ([Azat Khuzhin](https://github.com/azat)).
- Implement batch processing for aggregate functions with multiple nullable arguments. [#41058](https://github.com/ClickHouse/ClickHouse/pull/41058) ([Raúl Marín](https://github.com/Algunenano)).
- Speed up reading UniquesHashSet (`uniqState` from disk for example). [#41089](https://github.com/ClickHouse/ClickHouse/pull/41089) ([Raúl Marín](https://github.com/Algunenano)).
- Fixed high memory usage while executing mutations of compact parts in tables with huge number of columns. [#41122](https://github.com/ClickHouse/ClickHouse/pull/41122) ([lthaooo](https://github.com/lthaooo)).
- Enable the vectorscan library on ARM, this speeds up regexp evaluation. [#41033](https://github.com/ClickHouse/ClickHouse/pull/41033) ([Robert Schulze](https://github.com/rschu1ze)).
- Upgrade vectorscan to 5.4.8 which has many performance optimizations to speed up regexp evaluation. [#41270](https://github.com/ClickHouse/ClickHouse/pull/41270) ([Robert Schulze](https://github.com/rschu1ze)).
- Fix incorrect fallback to skip the local filesystem cache for VFS (like S3) which happened on very high concurrency level. [#40420](https://github.com/ClickHouse/ClickHouse/pull/40420) ([Kseniia Sumarokova](https://github.com/kssenii)).
- If row policy filter is always false, return empty result immediately without reading any data. This closes [#24012](https://github.com/ClickHouse/ClickHouse/issues/24012). [#40740](https://github.com/ClickHouse/ClickHouse/pull/40740) ([Amos Bird](https://github.com/amosbird)).
- Parallel hash JOIN for Float data types might be suboptimal. Make it better. [#41183](https://github.com/ClickHouse/ClickHouse/pull/41183) ([Alexey Milovidov](https://github.com/alexey-milovidov)).

#### Improvement[​](#improvement-3 "Direct link to Improvement")