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Alexey Milovidov 2022-08-18 10:32:26 +02:00
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* Added concurrency control logic to limit total number of concurrent threads created by queries. [#37558](https://github.com/ClickHouse/ClickHouse/pull/37558) ([Sergei Trifonov](https://github.com/serxa)). Add `concurrent_threads_soft_limit parameter` to increase performance in case of high QPS by means of limiting total number of threads for all queries. [#37285](https://github.com/ClickHouse/ClickHouse/pull/37285) ([Roman Vasin](https://github.com/rvasin)).
* Add `SLRU` cache policy for uncompressed cache and marks cache. ([Kseniia Sumarokova](https://github.com/kssenii)). [#34651](https://github.com/ClickHouse/ClickHouse/pull/34651) ([alexX512](https://github.com/alexX512)). Decoupling local cache function and cache algorithm [#38048](https://github.com/ClickHouse/ClickHouse/pull/38048) ([Han Shukai](https://github.com/KinderRiven)).
* Intel® In-Memory Analytics Accelerator (Intel® IAA) is a hardware accelerator available in the upcoming generation of Intel® Xeon® Scalable processors ("Sapphire Rapids"). Its goal is to speed up common operations in analytics like data (de)compression and filtering. ClickHouse gained the new "DeflateQpl" compression codec which utilizes the Intel® IAA offloading technology to provide a high-performance DEFLATE implementation. The codec uses the [Intel® Query Processing Library (QPL)](https://github.com/intel/qpl) which abstracts access to the hardware accelerator, respectively to a software fallback in case the hardware accelerator is not available. DEFLATE provides in general higher compression rates than ClickHouse's LZ4 default codec, and as a result, offers less disk I/O and lower main memory consumption. [#36654](https://github.com/ClickHouse/ClickHouse/pull/36654) ([jasperzhu](https://github.com/jinjunzh)). [#39494](https://github.com/ClickHouse/ClickHouse/pull/39494) ([Robert Schulze](https://github.com/rschu1ze)).
* Deduce way to sort based on input stream sort description. Skip sorting if input stream is already sorted. [#38719](https://github.com/ClickHouse/ClickHouse/pull/38719) ([Igor Nikonov](https://github.com/devcrafter)).
* `DISTINCT` in order with `ORDER BY`: improve memory usage (significantly) and query execution time + use `DistinctSortedChunkTransform` for final distinct when `DISTINCT` columns match `ORDER BY` columns, but rename to `DistinctSortedStreamTransform` in `EXPLAIN PIPELINE` → this improves memory usage significantly + remove unnecessary allocations in hot loop in `DistinctSortedChunkTransform`. [#39432](https://github.com/ClickHouse/ClickHouse/pull/39432) ([Igor Nikonov](https://github.com/devcrafter)). Use `DistinctSortedTransform` only when sort description is applicable to DISTINCT columns, otherwise fall back to ordinary DISTINCT implementation + it allows making less checks during `DistinctSortedTransform` execution. [#39528](https://github.com/ClickHouse/ClickHouse/pull/39528) ([Igor Nikonov](https://github.com/devcrafter)). Fix: `DistinctSortedTransform` didn't take advantage of sorting. It never cleared HashSet since clearing_columns were detected incorrectly (always empty). So, it basically worked as ordinary `DISTINCT` (`DistinctTransform`). The fix reduces memory usage significantly. [#39538](https://github.com/ClickHouse/ClickHouse/pull/39538) ([Igor Nikonov](https://github.com/devcrafter)).
* `DISTINCT` in order with `ORDER BY`: Deduce way to sort based on input stream sort description. Skip sorting if input stream is already sorted. [#38719](https://github.com/ClickHouse/ClickHouse/pull/38719) ([Igor Nikonov](https://github.com/devcrafter)). Improve memory usage (significantly) and query execution time + use `DistinctSortedChunkTransform` for final distinct when `DISTINCT` columns match `ORDER BY` columns, but rename to `DistinctSortedStreamTransform` in `EXPLAIN PIPELINE` → this improves memory usage significantly + remove unnecessary allocations in hot loop in `DistinctSortedChunkTransform`. [#39432](https://github.com/ClickHouse/ClickHouse/pull/39432) ([Igor Nikonov](https://github.com/devcrafter)). Use `DistinctSortedTransform` only when sort description is applicable to DISTINCT columns, otherwise fall back to ordinary DISTINCT implementation + it allows making less checks during `DistinctSortedTransform` execution. [#39528](https://github.com/ClickHouse/ClickHouse/pull/39528) ([Igor Nikonov](https://github.com/devcrafter)). Fix: `DistinctSortedTransform` didn't take advantage of sorting. It never cleared HashSet since clearing_columns were detected incorrectly (always empty). So, it basically worked as ordinary `DISTINCT` (`DistinctTransform`). The fix reduces memory usage significantly. [#39538](https://github.com/ClickHouse/ClickHouse/pull/39538) ([Igor Nikonov](https://github.com/devcrafter)).
* Use local node as first priority to get structure of remote table when executing `cluster` and similar table functions. [#39440](https://github.com/ClickHouse/ClickHouse/pull/39440) ([Mingliang Pan](https://github.com/liangliangpan)).
* Optimize filtering by numeric columns with AVX512VBMI2 compress store. [#39633](https://github.com/ClickHouse/ClickHouse/pull/39633) ([Guo Wangyang](https://github.com/guowangy)). For systems with AVX512 VBMI2, this PR improves performance by ca. 6% for SSB benchmark queries queries 3.1, 3.2 and 3.3 (SF=100). Tested on Intel Icelake Xeon 8380 * 2 socket. [#40033](https://github.com/ClickHouse/ClickHouse/pull/40033) ([Robert Schulze](https://github.com/rschu1ze)).
* Optimize index analysis with functional expressions in multi-thread scenario. [#39812](https://github.com/ClickHouse/ClickHouse/pull/39812) ([Guo Wangyang](https://github.com/guowangy)).