Re: When to use PARTITION BY HASH?

On 6/8/20 3:40 AM, Oleksandr Shulgin wrote:
[snip]

I've found the original commit adding this feature in version 11: https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=1aba8e651ac3e37e1d2d875842de1e0ed22a651e

It says:

"Hash partitioning is useful when you want to partition a growing data
set evenly.  This can be useful to keep table sizes reasonable, which
makes maintenance operations such as VACUUM faster, or to enable
partition-wise join."

How does hashed (meaning "randomly?) distribution of records make partition-wise joins more efficient?

Or -- since I interpret that as having to do with "locality of data" -- am I misunderstanding the meaning of "partition-wise joins"?