"Li, Zheng" <zhelli(at)amazon(dot)com> writes:
> This patch enables correlated IN/Any subquery to be transformed to join, the transformation is allowed only when the correlated Var is in the where clause of the subquery. It covers the most common correlated cases and follows the same criteria that is followed by the correlated Exists transformation code.
It's too late to include this in v13, but please add the patch to the
next commitfest so that we remember to consider it for v14.
https://commitfest.postgresql.org
regards, tom lane