Greg Stark <gsstark(at)mit(dot)edu> writes:
> I'm not clear on what truncate_useless_pathkeys is doing.
It's throwing away pathkey info that isn't relevant for the current
query (and would cause the planner to consider a multi-column-index
scan as better-ordered than a scan of an index with fewer columns,
when no such thing is true if the extra columns aren't relevant).
> If it were changed to just keep the suffix would that break other things?
Yes, that would be completely backwards.
regards, tom lane