c64de21e96
In an example such as SELECT * FROM i LEFT JOIN LATERAL (SELECT * FROM j WHERE i.n = j.n) j ON true; it is safe to pull up the LATERAL subquery into its parent, but we must then treat the "i.n = j.n" clause as a qual clause of the LEFT JOIN. The previous coding in deconstruct_recurse mistakenly labeled the clause as "is_pushed_down", resulting in wrong semantics if the clause were applied at the join node, as per an example submitted awhile ago by Jeremy Evans. To fix, postpone processing of such clauses until we return back up to the appropriate recursion depth in deconstruct_recurse. In addition, tighten the is-safe-to-pull-up checks in is_simple_subquery; we previously missed the possibility that the LATERAL subquery might itself contain an outer join that makes lateral references in lower quals unsafe. A regression test case equivalent to Jeremy's example was already in my commit of yesterday, but was giving the wrong results because of this bug. This patch fixes the expected output for that, and also adds a test case for the second problem.
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