What ClickHouse/ClickHouse shipped
Written by FoxPlug from public releases; not affiliated with Clickhouse. An automatic summary of the public release, pull request and commit data of github.com/ClickHouse/ClickHouse. Clickhouse did not write it and does not use or endorse FoxPlug. Every line links to the public change it describes.
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Week of September 21, 2026
What shipped
- clickhouse-server now applies a seccomp system call filter at startup to restrict kernel interfaces available to the process [27] Pull request #119545
- substring(s, 1) and substringUTF8(s, 1) now return the input column directly without creating a copy for String types [1] Pull request #119820
- arrayHasSubstr skips KMP preprocessing when the needle cannot fit in the haystack [2] Pull request #119824
- positionCaseInsensitiveUTF8 now gives consistent results regardless of whether arguments are constant or column values [9] Pull request #122113
- INSERT ... SELECT is now compatible with async insert for eligible single-block local inserts [36] Pull request #111663
- Azure blob storage reads now correctly reopen when a response ends before the right bound [0] Pull request #120963
- Query tree passes now preserve FunctionKind::WINDOW when rewriting aggregate functions [21] Pull request #119681
promql_evaluation_timeis now stored as double instead of float to prevent silent rounding [8] Pull request #120942- Column statistics are no longer kept for columns removed by column TTL [30] Pull request #122058
- format() function now correctly handles escaped braces surrounding replacement fields [4] Pull request #120704
Why it matters
This week includes security improvements through seccomp filtering, several performance optimizations for string and array functions, and bug fixes for distributed queries, string handling, and storage operations. These changes address both performance scaling issues and correctness problems across various query types.
Changelog entry
- clickhouse-server now applies a seccomp system call policy at startup to restrict available kernel interfaces Pull request #119545
- Performance: substring(s, 1) and substringUTF8(s, 1) now return the input column directly for String types without copying Pull request #119820
- Performance: arrayHasSubstr skips KMP preprocessing when haystack is shorter than needle Pull request #119824
- Fixed positionCaseInsensitiveUTF8 giving different results for constant and column arguments Pull request #122113
- Async insert now supports eligible single-block local INSERT ... SELECT queries Pull request #111663
- Fixed Azure blob storage reads not reopening when response ends before right bound Pull request #120963
- Fixed window function kind not being preserved when query tree passes rewrite aggregate functions Pull request #119681
- Fixed
promql_evaluation_timesilently rounding by storing as double instead of float Pull request #120942 - Fixed column statistics being kept for columns removed by column TTL Pull request #122058
- Fixed format() function throwing error on escaped braces surrounding replacement fields Pull request #120704
ClickHouse now applies seccomp filtering at startup for improved containment. This week also brings performance optimizations for substring operations, array searches, and CSV reading, plus fixes for UTF8 case-insensitive search consistency.
ClickHouse continues improving security and performance. This week's updates include seccomp system call filtering at server startup for enhanced containment, performance optimizations for substring operations and array functions, and important fixes for UTF8-aware string operations and distributed query handling. These changes address both kernel interface containment and query execution consistency.
Week of September 14, 2026
What shipped
- Removed the query analysis that preceded the analyzer, completing the transition to the new analyzer as the sole query analysis path. Pull request #120311
- Fixed a critical security issue where HDFS database table cache did not check read source grants and host filters. Pull request #119523
- Fixed query-local text index caches to use plain LRU instead of a different cache policy. Pull request #120844
- Merged join-order conflict-detector settings into a single enum setting to reduce configuration complexity. Pull request #120630
- Added validation that Azure endpoint range responses match the requested offset to prevent data corruption from proxies that ignore range requests. Pull request #120955
- Fixed incorrect aggregate results when limit pushdown optimization was used with ORDER BY as a strict prefix of GROUP BY. Pull request #117573
- Changed server behavior to not terminate on retryable errors while loading outdated parts. Pull request #117981
- Fixed correlated subqueries in SELECT list to work correctly when the outer query has a WHERE clause. Pull request #118402
- Fixed parameterized views to work correctly when referenced by their own name in the analyzer. Pull request #120698
- Fixed WHERE f IN (nan) to not silently lose NaN rows from floating-point columns during statistics-based pruning. Pull request #117453
Why it matters
This week includes important stability fixes for query analysis, security hardening for cloud storage, and correctness fixes for aggregations and floating-point handling. The removal of legacy query analysis code simplifies the codebase after the analyzer became the default. Several edge-case bugs affecting correlated subqueries, parameterized views, and NaN handling have been resolved.
Changelog entry
- Removed legacy query analysis code that preceded the analyzer. Pull request #120311
- Fixed HDFS database to check read source grant and host filter when serving cached tables. Pull request #119523
- Fixed query-local text index caches to use plain LRU. Pull request #120844
- Added validation that Azure endpoint range responses match requested offset. Pull request #120955
- Fixed incorrect aggregates from limit pushdown when ORDER BY is a strict prefix of GROUP BY. Pull request #117573
- Server no longer terminates on retryable errors while loading outdated parts. Pull request #117981
- Fixed correlated subqueries in SELECT list to work with WHERE clauses. Pull request #118402
- Fixed parameterized views to work when referenced by their own name. Pull request #120698
- Fixed WHERE f IN (nan) to preserve NaN rows in floating-point columns. Pull request #117453
- Fixed formatDateTime functions to work with LowCardinality time zone arguments. Pull request #117006
New in ClickHouse: removed legacy query analysis code, fixed Azure range validation, secured HDFS table cache access checks, and resolved query correctness issues with correlated subqueries and NaN handling.
This week's ClickHouse updates focus on stability and correctness: we completed the transition to the new analyzer by removing legacy query analysis code; fixed a critical security issue in HDFS database table caching that wasn't enforcing read source grants; improved Azure Blob Storage reliability with range offset validation; resolved query correctness bugs affecting correlated subqueries, parameterized views, and floating-point NaN handling; and merged query optimization settings for cleaner configuration.