Christophe Pettus explains the enable_parallel_append GUC, which allows PostgreSQL to distribute workers across multiple partitions or UNION branches simultaneously rather than sequentially. This shift from sequential to parallel execution across append nodes aims to improve throughput for complex queries involving large unions or partitioned tables.
- Parallel Append executes branches concurrently, not one after another
- Enable via enable_parallel_append GUC to change execution strategy
- Beneficial for large UNION queries or wide partitioned table scans
- Workers are distributed across branches to maximize resource usage
- Check execution plans to verify parallel append is actually used