Optimize table (force merge)

Force merging of all parts (use with caution on large tables)

clickhouse-client -q 'OPTIMIZE TABLE mydb.mytable FINAL'
tool
clickhouse17 commands
tags
clickhouse

More clickhouse commands

  • Ingest CSV from file
    clickhouse-client --query 'INSERT INTO mydb.events FORMAT CSVWithNames' < events.csv

    Bulk-load a CSV file into a ClickHouse table

  • Check replication status
    clickhouse-client -q 'SELECT database, table, is_leader, queue_size, absolute_delay FROM system.replicas WHERE absolute_delay > 0'

    Show replication lag on delayed replicas

  • Slowest recent queries
    clickhouse-client -q "SELECT query_duration_ms, formatReadableSize(memory_usage) mem, substring(query,1,80) FROM system.query_log WHERE type=2 AND event_time>now()-3600 ORDER BY query_duration_ms DESC LIMIT 10"

    Top slow finished queries last hour with memory; type=2 = QueryFinish

  • Pending mutations
    clickhouse-client -q "SELECT database, table, mutation_id, latest_fail_reason FROM system.mutations WHERE is_done=0"

    Find stuck ALTER/DELETE mutations with failure reason; blocks schema changes

  • Connect to clickhouse-client
    clickhouse-client -h clickhouse -u default --password <pass> --database mydb

    Open interactive ClickHouse CLI session

all 17 clickhouse commands