2025 Changelog

ClickHouse release v25.5.8.13-stable (b594fb9739e) FIXME as compared to v25.5.7.52-stable (6e66ab95d8a)

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

• Backported in #83209: Fix performance degradation in SummingMergeTree that was intorduced in 25.5 in https://github.com/ClickHouse/ClickHouse/pull/79051. #82130 (Pavel Kruglov).
• Backported in #83199: Do not check for cyclic dependencies on create table with no dependencies. It fixes performance degradation of the use cases with creation of thousands of tables that was introduced in https://github.com/ClickHouse/ClickHouse/pull/65405. #83077 (Pavel Kruglov).
• Backported in #83473: Fix possible crash in Variant type in UNION. #83295 (Pavel Kruglov).
• Backported in #83764: Keeper fix: update total watch count correctly when ephemeral nodes are deleted on session close. #83583 (Antonio Andelic).

NOT FOR CHANGELOG / INSIGNIFICANT

• Backported in #83813: hold the temporary part lock when executeReplaceRange. #83095 (Sema Checherinda).
• Backported in #83864: Allow concurrent tables creation when max_database_replicated_create_table_thread_pool_size setting is 0 (automatic pool size). #83834 (Alexander Tokmakov).