ClickHouse/docs/changelogs/v21.2.6.1-stable.md

ClickHouse release v21.2.6.1-stable FIXME as compared to v21.2.5.5-stable

Bug Fix

• Backported in #21352: Fix the number of threads for scalar subqueries and subqueries for index (after #19007 single thread was always used). Fixes #20457, #20512. #20550 (Nikolai Kochetov).
• Backported in #21262: fix default_replica_path and default_replica_name values are useless on Replicated(*)MergeTree engine when the engine needs specify other parameters. #21060 (mxzlxy).
• Backported in #21156: fix bug related to cast tuple to map. Closes #21029. #21120 (hexiaoting).
• Backported in #21234: Now mutations allowed only for table engines that support them (MergeTree family, Memory, MaterializedView). Other engines will report a more clear error. Fixes #21168. #21183 (alesapin).
• Backported in #21427: Fix crash in EXPLAIN for query with UNION. Fixes #20876, #21170. #21246 (flynn).
• Backported in #21301: Fix redundant reconnects to ZooKeeper and the possibility of two active sessions for a single clickhouse server. Both problems introduced in #14678. #21264 (alesapin).
• Backported in #21553: Now ALTER MODIFY COLUMN queries will correctly affect changes in partition key, skip indices, TTLs, and so on. Fixes #13675. #21334 (alesapin).
• Backported in #21380: Fix error Bad cast from type ... to DB::ColumnLowCardinality while inserting into table with LowCardinality column from Values format. Fixes #21140. #21357 (Nikolai Kochetov).