parallel_query_dsa
Waiting for parallel query dynamic shared memory allocation lock.
Additional Information​
During Parallel operations Dynamic Shared Areas of memory (DSA) are allocated. This wait is seen while waiting for the allocation lock.
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.
Avoid spilling to disk. The shared hash table should if possible remain in memory. Adjust work_mem to ensure this happens where practical and be aware that the total memory allocated is work_mem * workers.
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.
Additional Links​
PostgreSQL documentation - Parallel Query
PostgreSQL documentation - The Statistics Collector
EDB - Parallel Hash Joins in PostgreSQL Explained
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