postgres join - ghdrako/doc_snipets GitHub Wiki

Nested Loop Join

• no parallel-aware mode

Merge Join

hash join

Think of Hash Join as a kind of Nested Loop Join that builds its own index up front every time, which makes it good for joins against things you don't have an index for or joins against whole tables where sequential access beats random access.

parallel hash join 11+

• https://www.enterprisedb.com/postgres-tutorials/parallel-hash-joins-postgresql-explained
• Parallel Join Algorithms (Hashing) (or just the slides)

enable_parallel_hash = [on|off]