Storage Optimization

Compression Codecs

• Default: LZ4 — fast, moderate compression
• ZSTD(level) — better compression, slower. Level 1-22 (3 is good default)
• Delta + ZSTD — excellent for time-series monotonic data
• DoubleDelta — best for timestamps and counters
• Gorilla — optimized for floating-point gauge metrics
• T64 — for integer columns with small range
• Per-column: ALTER TABLE t MODIFY COLUMN col TYPE UInt32 CODEC(Delta, ZSTD(3))
• In-place codec change: ALTER TABLE t MODIFY COLUMN col CODEC(Delta, ZSTD(3))

TTL Policies

• Table-level: ALTER TABLE t MODIFY TTL event_time + INTERVAL 90 DAY
• Column-level: ALTER TABLE t MODIFY COLUMN old_col TTL event_time + INTERVAL 30 DAY
• Move to volume: TTL event_time + INTERVAL 7 DAY TO VOLUME 'cold'
• Delete: TTL event_time + INTERVAL 365 DAY DELETE
• Monitor TTL merges: system.merges WHERE is_ttl_merge = 1