Richard Guo <ri...@pivotal.io> writes:
> Currently we do not try to pull up sub-select of type ANY_SUBLINK if it
> refers to any Vars of the parent query, as indicated in the code snippet
> below:
> if (contain_vars_of_level((Node *) subselect, 1))
> return NULL;
> Why do we have this check?
Because the result would not be a join between two independent tables.
> Can we try to pull up direct-correlated ANY SubLink with the help of
> LATERAL?
Perhaps. But what's the argument that you'd end up with a better
plan? LATERAL pretty much constrains things to use a nestloop,
so I'm not sure there's anything fundamentally different.
regards, tom lane
