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Hash_Batch_Loading

Short Description

A process is waiting for other parallel hash participants to finish loading a hash table.

Additional Information

In parallel hash joins, work is split between background worker processes. This wait is seen where other parallel hash participants are yet to finish loading a hash table.

How to reduce this wait

Parallel queries are excellent at scanning large amounts of data the quickly returning results. Run in isolation or in a considered manner they are a useful tool.

Do not allow concurrent parallel queries from many users to flood system CPU or IO resources.

Adjust max_worker_process , max_parallel_workers and max_parallel_workers_per_gather to control response of your query and overall impact to the system.

PostgreSQL documentation - Parallel Query

PostgreSQL documentation - The Statistics Collector

EDB - Parallel Hash Joins in PostgreSQL Explained

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