On Wed, May 31, 2023 at 10:47 AM Richard Guo <guofengli...@gmail.com> wrote:
> On Tue, May 30, 2023 at 10:48 PM Markus Winand <markus.win...@winand.at> > wrote: > >> I found an error similar to others before ([1]) that is still persists as >> of head right now (0bcb3ca3b9). >> >> CREATE TABLE t ( >> n INTEGER >> ); >> >> SELECT * >> FROM (VALUES (1)) t(c) >> LEFT JOIN t ljl1 ON true >> LEFT JOIN LATERAL (WITH cte AS (SELECT * FROM t WHERE t.n = ljl1.n) >> SELECT * FROM cte) ljl2 ON ljl1.n = 1; >> >> ERROR: wrong varnullingrels (b 3) (expected (b)) for Var 2/1 >> >> Note that the error does **not** occur if the CTE is unwrapped like this: >> >> SELECT * >> FROM (VALUES (1)) t(c) >> LEFT JOIN t ljl1 ON true >> LEFT JOIN LATERAL (SELECT * FROM t WHERE t.n = ljl1.n) ljl2 ON ljl1.n = >> 1; > > > Thanks for the report! Reproduced here. Also it can be reproduced with > subquery, as long as the subquery is not pulled up. > > SELECT * > FROM (VALUES (1)) t(c) > LEFT JOIN t ljl1 ON true > LEFT JOIN LATERAL (SELECT * FROM t WHERE t.n = ljl1.n offset 0) ljl2 ON > ljl1.n = 1; > ERROR: wrong varnullingrels (b 3) (expected (b)) for Var 2/1 > > When we transform the first form of identity 3 to the second form, we've > converted Pb*c to Pbc in deconstruct_distribute_oj_quals. But we > neglect to consider that rel C might be a RTE_SUBQUERY and contains > quals that have lateral references to B. So the B vars in such quals > have wrong nulling bitmaps and we'd finally notice that when we do > fix_upper_expr for the NestLoopParam expressions. > We can identify in which form of identity 3 the plan is built up by checking the relids of the B/C join's outer rel. If it's in the first form, the outer rel's relids must contain the A/B join. Otherwise it should only contain B's relid. So I'm considering that maybe we can adjust the nulling bitmap for nestloop parameters according to that. Attached is a patch for that. Does this make sense? Thanks Richard
v1-0001-Fix-nulling-bitmap-for-nestloop-parameters.patch
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