Teja Jakkidi <teja.jakkidi05@xxxxxxxxx> writes: > 1. What is a worker process exactly in Postgres? It's a background process that can be started if the planner decides that a particular query would benefit from parallelization. If so, the original session process (the "leader") cooperates with one or more temporarily-spawned workers to perform the query. > 2. is max_parallel_workers specific to a session or instance. My max_parallel_workers is set to 8. If it is specific to instance, does it mean at any point of time I can only see 8 parallel processes despite the number of transactions in the db? Per instance. There is a different knob max_parallel_workers_per_gather that gives you some control over how many workers a given leader will try to use. Before you say "oh, I've got max_connections set to 100, so I'd better raise max_parallel_workers to a few hundred" ... don't do that unless you've got a few hundred CPUs in the machine. While session processes might be sitting around doing nothing much except waiting for the next query, workers generally are busy throughout their lifespan. So it's counterproductive for max_parallel_workers to be more than roughly the number of available CPUs --- setting it higher just encourages the system to create parallel workers that it can't use effectively. > 3. Does number of worker process have anything to do with active connections to the database. See above. regards, tom lane
