25.8.16.10001 Altinity Stable

Changes compared to upstream's v25.8.16.34-lts

Backward Incompatible Changes

• ALTER MODIFY COLUMN now requires explicit DEFAULT when converting nullable columns to non-nullable types. Previously such ALTERs could get stuck with cannot convert null to not null errors, now NULLs are replaced with column's default expression (ClickHouse#84770 by @vdimir via #1344)

New Features

• Added new SQL statement EXECUTE AS to support user impersonation (ClickHouse#70775 by @shiyer7474, ClickHouse#90437 by @alexbakharew via #1340)

Critical Bug Fixes

• Fix crash in StorageDistributed when parsing malformed shard directory names (ClickHouse#90243 by @AVMusorin via #1343)

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

• Now datalakes catalogs will be shown in system introspection tables only if show_data_lake_catalogs_in_system_tables explicitly enabled (ClickHouse#88341 by @alesapin via #1331)
• Now ClickHouse will show data lake catalog database in SHOW DATABASES query by default (ClickHouse#89914 by @alesapin via #1331)
• Possible crash/undefined behavior in IN function where primary key column types are different from IN function right side column types (ClickHouse#89367 by @ilejn via #1339)
• Fixed move-to-prewhere optimization, which did not work in the presence of row policy (ClickHouse#87303 by @KochetovNicolai via #1345)
• Fixes a bug where certain distributed queries with ORDER BY could return ALIAS columns with swapped values (i.e., column a showing column b’s data and vice versa) (ClickHouse#94644 by @filimonov via #1346)
• Split part ranges by volume characteristics to enable TTL drop merges for cold volumes. After this patch, parts with a max TTL < now will be removed from cold storage. The algorithm will schedule only single part drops. (ClickHouse#90059 by @Michicosun via #1363)
• Check and mark the interserver IO address active in DDL worker (ClickHouse#92339 by @tuanpach via #1403)
• Disable write_marks_for_substreams_in_compact_parts by default to preserve downgrade compatibility (#1407 by @zvonand)

Improvements

• Fix handling of users with a dot in the name when added via config file (ClickHouse#86633 by @mkmkme via #1342)
• S3Queue auxiliary Zookeeper support using keeper_path setting from s3Queue (ClickHouse#95203 by @lesandie via #1357)

Performance Improvements

• SELECT query with FINAL clause on a ReplacingMergeTree table with the is_deleted column now executes faster because of improved parallelization from 2 existing optimizations (ClickHouse#88090 by @shankar-iyer via #1332)
• Reduce INSERT/merges memory usage with wide parts for very wide tables by enabling adaptive write buffers. Add support of adaptive write buffers for encrypted disks (ClickHouse#92250 by @azat via #1341)

Not for changelog

• Altinity branding patches

Build report

Release notes

Packages

Available for both AMD64 and Aarch64 from https://builds.altinity.cloud/ as either .deb, .rpm, or .tgz

Docker images

Available for both AMD64 and Aarch64: altinity/clickhouse-server/25.8.16.10001.altinitystable