Re: Parallel query execution

I mentioned last year that I wanted to start working on parallelism:

https://wiki.postgresql.org/wiki/Parallel_Query_Execution

I believe it is time to start adding parallel execution to the backend.

We already have some parallelism in the backend:

effective_io_concurrency and helper processes. I think it is time we

start to consider additional options

Parallelism isn't going to help all queries, in fact it might be just a

small subset, but it will be the larger queries. The pg_upgrade

parallelism only helps clusters with multiple databases or tablespaces,

but the improvements are significant.