ClickHouse Release 26.7

Summary

ClickHouse 26.7 is a monthly release with 61 new features, 112 performance optimizations, and 329 bug fixes, including improvements to aggregation, joins, vector search, phrase search, query analysis, and URL access. Its combination of optimize_aggregation_in_order and the new optimize_aggregation_in_order_limit turns matching GROUP BY, ORDER BY, and LIMIT queries into low-memory streaming pipelines that can stop reading after N groups. In a TPC-H scale-factor-100 test, the optimized query ran 313× faster, processed 339× fewer rows, and used 592× less peak memory. The release also adds build-side JOIN pruning, LLVM JIT compilation for supported regular expressions, and macOS improvements including faster allocation-heavy workloads, concurrent remote-replica reads, SSD cache dictionaries, FileLog, and STREAM support.

Takeaways

1. 1

   Combining optimize_aggregation_in_order with optimize_aggregation_in_order_limit allows ClickHouse to retain only the current ordered group, emit completed groups, and stop reading after the requested LIMIT.

2. 2

   In a TPC-H scale-factor-100 benchmark, the optimized GROUP BY query ran in 0.009 seconds versus 2.814 seconds, processed 1.77 million instead of 600.04 million rows, and reduced peak memory from 17.33 GiB to 29.97 MiB.

3. 3

   The new regular-expression engine uses LLVM to compile supported patterns into CPU-specific native code, falls back transparently when needed, and reduced match() time over 20 million strings from 2.7 seconds to 1.1 seconds.