BUG #16065: The operation nodes in query plans outputted by EXPLAIN have no authoritative definitions.

The following bug has been logged on the website:

Bug reference:      16065
Logged by:          Eric Toombs
Email address:      ewtoombs@uwaterloo.ca
PostgreSQL version: 12.0
Operating system:   any
Description:

The official documentation of EXPLAIN is here:
https://www.postgresql.org/docs/current/sql-explain.html

It's a start, but it doesn't actually define any of the operation nodes in
the query plan tree it outputs, e.g. Seq Scan, Index Scan, Index Only Scan,
HashAggregate, Nested Loop, Nested Loop Semi Join, Nested Loop Anti Join,
etc.. Online, there are descriptions (i.e. guesses) of what each operation
node is actually doing, but these descriptions are not authoritative.

With authoritative definitions of each operation node, there would be no
more guesswork, and DBAs could have a much more reliable mental model of
what a query plan actually does.