2025 Changelog

- New parquet reader implementation. It's generally faster and supports page-level filter pushdown and PREWHERE. Currently experimental. Use setting `input_format_parquet_use_native_reader_v3` to enable. [#82789](https://github.com/ClickHouse/ClickHouse/pull/82789) ([Michael Kolupaev](https://github.com/al13n321)).
- Replaced the official HTTP transport in Azure library with our own HTTP client implementation for Azure Blob Storage. Introduced multiple settings for this clients which mirror settings from S3. Introduced aggressive connection timeouts for both Azure and S3. Improved introspection into Azure profile events and metrics. New client is enabled by default, provide much better latencies for cold queries on top of Azure Blob Storage. Old `Curl` client can be returned back by setting `azure_sdk_use_native_client=false`. [#83294](https://github.com/ClickHouse/ClickHouse/pull/83294) ([alesapin](https://github.com/alesapin)). The previous, official implementation of Azure client was unsuitable for production due to terrible latency spikes, ranging from five seconds to minutes. We have ditched that terrible implementation and are very proud of that.
- Processes indexes in increasing order of file size. The net index ordering prioritizes minmax and vector indexes (due to simplicity and selectivity respectively), and small indexes thereafter. Within the minmax/vector indexes smaller indexes are also preferred. [#84094](https://github.com/ClickHouse/ClickHouse/pull/84094) ([Maruth Goyal](https://github.com/maruthgoyal)).
- Enable MergeTree setting `write_marks_for_substreams_in_compact_parts` by default. It significantly improves performance of subcolumns reading from newly created Compact parts. Servers with version less then 25.5 won't be able to read new Compact parts. [#84171](https://github.com/ClickHouse/ClickHouse/pull/84171) ([Pavel Kruglov](https://github.com/Avogar)).
- `azureBlobStorage` table engine: cache and reuse managed identity authentication tokens when possible to avoid throttling. [#79860](https://github.com/ClickHouse/ClickHouse/pull/79860) ([Nick Blakely](https://github.com/niblak)).
- `ALL` `LEFT/INNER` JOINs will be automatically converted to `RightAny` if the right side is functionally determined by the join key columns (all rows have unique join key values). [#84010](https://github.com/ClickHouse/ClickHouse/pull/84010) ([Nikita Taranov](https://github.com/nickitat)).
- Add `max_joined_block_size_bytes` in addition to `max_joined_block_size_rows` to limit the memory usage of JOINs with heavy columns. [#83869](https://github.com/ClickHouse/ClickHouse/pull/83869) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).
- Added new logic (controlled by the setting `enable_producing_buckets_out_of_order_in_aggregation`, enabled by default) that allows sending some buckets out of order during memory-efficient aggregation. When some aggregation buckets take significantly longer to merge than others, it improves performance by allowing the initiator to merge buckets with higher bucket id-s in the meantime. The downside is potentially higher memory usage (shouldn't be significant). [#80179](https://github.com/ClickHouse/ClickHouse/pull/80179) ([Nikita Taranov](https://github.com/nickitat)).
- Introduced the `optimize_rewrite_regexp_functions` setting (enabled by default), which allows the optimizer to rewrite certain `replaceRegexpAll`, `replaceRegexpOne`, and `extract` calls into simpler and more efficient forms when specific regular expression patterns are detected. (issue [#81981](https://github.com/ClickHouse/ClickHouse/issues/81981)). [#81992](https://github.com/ClickHouse/ClickHouse/pull/81992) ([Amos Bird](https://github.com/amosbird)).
- Process `max_joined_block_rows` outside of hash JOIN main loop. Slightly better performance for ALL JOIN. [#83216](https://github.com/ClickHouse/ClickHouse/pull/83216) ([Nikolai Kochetov](https://github.com/KochetovNicolai)).
- Process higher granularity min-max indexes first. Closes [#75381](https://github.com/ClickHouse/ClickHouse/issues/75381). [#83798](https://github.com/ClickHouse/ClickHouse/pull/83798) ([Maruth Goyal](https://github.com/maruthgoyal)).
- Make `DISTINCT` window aggregates run in linear time and fix a bug in `sumDistinct`. Closes [#79792](https://github.com/ClickHouse/ClickHouse/issues/79792). Closes [#52253](https://github.com/ClickHouse/ClickHouse/issues/52253). [#79859](https://github.com/ClickHouse/ClickHouse/pull/79859) ([Nihal Z. Miaji](https://github.com/nihalzp)).
- Vector search queries using a vector similarity index complete with lower latency due to reduced storage reads and reduced CPU usage. [#83803](https://github.com/ClickHouse/ClickHouse/pull/83803) ([Shankar Iyer](https://github.com/shankar-iyer)).
- Rendezvous hashing for improve cache locality of workload distribution among parallel replicas. [#82511](https://github.com/ClickHouse/ClickHouse/pull/82511) ([Anton Ivashkin](https://github.com/ianton-ru)).
- Implement addManyDefaults for If combinators, so now aggregate functions with If combinators work faster. [#83870](https://github.com/ClickHouse/ClickHouse/pull/83870) ([Raúl Marín](https://github.com/Algunenano)).
- Calculate serialized key columnarly when group by multiple string or number columns. [#83884](https://github.com/ClickHouse/ClickHouse/pull/83884) ([李扬](https://github.com/taiyang-li)).
- Eliminated full scans for the cases when index analysis results in empty ranges for parallel replicas reading. [#84971](https://github.com/ClickHouse/ClickHouse/pull/84971) ([Eduard Karacharov](https://github.com/korowa)).
- Try -falign-functions=64 in attempt for more stable perf tests. [#83920](https://github.com/ClickHouse/ClickHouse/pull/83920) ([Azat Khuzhin](https://github.com/azat)).
- The bloom filter index is now used for conditions like `has([c1, c2, ...], column)`, where `column` is not of an `Array` type. This improves performance for such queries, making them as efficient as the `IN` operator. [#83945](https://github.com/ClickHouse/ClickHouse/pull/83945) ([Doron David](https://github.com/dorki)).
- Reduce unnecessary memcpy calls in CompressedReadBufferBase::readCompressedData. [#83986](https://github.com/ClickHouse/ClickHouse/pull/83986) ([Raúl Marín](https://github.com/Algunenano)).
- Optimize `largestTriangleThreeBuckets` by removing temporary data. [#84479](https://github.com/ClickHouse/ClickHouse/pull/84479) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
- Optimize string deserialization by simplifying the code. Closes [#38564](https://github.com/ClickHouse/ClickHouse/issues/38564). [#84561](https://github.com/ClickHouse/ClickHouse/pull/84561) ([Alexey Milovidov](https://github.com/alexey-milovidov)).
- Fixed the calculation of the minimal task size for parallel replicas. [#84752](https://github.com/ClickHouse/ClickHouse/pull/84752) ([Nikita Taranov](https://github.com/nickitat)).
- Improved performance of applying patch parts in `Join` mode. [#85040](https://github.com/ClickHouse/ClickHouse/pull/85040) ([Anton Popov](https://github.com/CurtizJ)).