Optimizing parallel_hash

Purpose

The parallel_hash algorithm is an optimization mechanism in ClickHouse to accelerate hash operations (especially for the GROUP BY operation). It improves performance through parallel processing.

Procedure

1. Log in to ClickHouse client.

   clickhouse -m -n

2. Enable the parallel_hash algorithm.

   set join_algorithm='parallel_hash';

   

3. Exit the ClickHouse client.

   quit;