"Chris Velevitch" <chris(dot)velevitch(at)gmail(dot)com> writes:
> I'm trying to understand the explain output, but I can't find any
> references to the meanings of the following terms:-
> merge join
> nested loop
> merge left join
> nested loop left join
http://developer.postgresql.org/pgdocs/postgres/planner-optimizer.html
regards, tom lane