PostgreSQL enable_parallel_hash reduces memory pressure via shared worker pools
The enable_parallel_hash GUC allows parallel hash join workers to pool their memory to build a single shared hash table instead of each worker constructing its own independent copy. This architectural shift significantly lowers total memory consumption during parallel query execution. The optimization is particularly impactful for workloads that previously suffered from memory exhaustion due to redundant hash table creation across multiple workers.
Reduces total memory usage by sharing one hash table across all parallel workers
