2025 Changelog

ClickHouse release v25.8.9.20-lts (a1f4cd9c23f) FIXME as compared to v25.8.8.26-lts (8a247503308)

Improvement

• Backported in #87979: Filesystem cache improvement: reuse cache priority iterator among threads concurrently reserving space in cache. #87914 (Kseniia Sumarokova).
• Backported in #88060: To expose the KeeperRequestRejectedDueToSoftMemoryLimitCount keeper profile event, we must add it to KeeperConstants.cpp. #88030 (Miсhael Stetsyuk).

Bug Fix (user-visible misbehavior in an official stable release)

• Backported in #87777: Avoid leaking of tracked memory for async logging (can have a significant drift, for 10 hours, ~100GiB) and text_log (almost same drift is possible). #87584 (Azat Khuzhin).
• Backported in #87909: Fix several skip indices bugs. #87817 (Raúl Marín).
• Backported in #88073: Fix merge with projections when the last block is empty. #87928 (Raúl Marín).
• Backported in #88147: Fixed possible data corruption in MergeTree tables with set column TTL. #88095 (Anton Popov).

Build/Testing/Packaging Improvement

• Backported in #87882: Use postgres 18.0. #87647 (Konstantin Bogdanov).

NOT FOR CHANGELOG / INSIGNIFICANT

• Backported in #87940: Integration tests: Replace missing bitnami images. #87897 (Nikita Fomichev).
• Backported in #88023: Add logs to S3 Client. #88001 (Julia Kartseva).