v2.6.42

NEW FEATURES

• apply object disk key rewriting for remapped tables during restore to prevent data corruption when using --restore-database-mapping or --restore-table-mapping with object disks (S3/GCS/Azure), fix 1278
• add GCS customer-supplied encryption key (CSEK) support for client-side encryption where the encryption key is controlled by the user, not Google. Use GCS_ENCRYPTION_KEY environment variable or gcs.encryption_key config option with base64-encoded 256-bit key, fix 1316
• add TLS support for Keeper connections, allows secure connections to ClickHouse Keeper with SSL/TLS certificates, fix 1312
• add --skip-empty-tables option to restore and restore_remote commands to skip tables with no data during restore, available in CLI, API handlers, and server mode, fix 1265

IMPROVEMENTS

• implements batching keys deletions to improve speed of delete old backups during backup retention, fix 1066
• add ClickHouse 25.12 to test matrix
• add example for minimal grants for backup user in Examples.md
• improve GCS connection handling: properly close readers on error to prevent goroutine leaks, change retry logging from Debug to Warn level
• use partitionId directly instead of INSERT INTO temp table for ClickHouse 21.8+, improves partition handling performance, fix 1315
• refactor table column type checking to use single query before freeze operation instead of per-table queries fix 1194
• add KEEPER_TLS_ENABLES=1 by default in integration tests
• improve TestKeeperTLS, TestReplicatedCopyToDetached, and TestRestoreDistributedCluster test stability
• update GitHub Actions workflows and GOROOT configuration
• explain S3_FORCE_PATH_STYLE configuration option in documentation

BUG FIXES

• fix S3 multipart operations (upload, download, copy) to respect S3_MAX_PARTS_COUNT instead of hardcoded 10000 value, allows S3-compatible backends with stricter limits
• fix GCS credential conflicts when multiple authentication options are provided, refactor GCS Connect to avoid conflicting client options
• fix COS upload for large files, fix 1318
• fix list status update in server mode, fix 1317
• fix TestServerAPI and TestReplicatedCopyToDetached test failures in CI/CD
• fix OpenSSL/client config parsing for Keeper TLS connections, add comprehensive integration tests
• fix partition filtering when using --restore-database-mapping, --restore-table-mapping together with --partitions option
• security: update dependencies to fix CVE-2025-61729, CVE-2025-61727