> Skipping every GROUP BY item that contains no level-zero Var is too
> broad. The item in that query is a Const, so it contains no Var, and
> the commit exists to keep it a candidate. The constants that must not
> be replaced are the other Const nodes that happen to compare equal.
We might need to special-case TLEs that are identified this way.
The basic problem is how do you tell which Consts are okay to replace,
and what I'm saying is "none of them, except the identified TLE".
Agreed.
None of the Consts should be replaced, except the targetlist
entry that GROUP BY identified.
That entry already carries a ressortgroupref. When its expression is a
Const or Param, substitute_grouped_columns_mutator() replaces the entry
as a whole. The match is on ressortgroupref, because groupClauses may
be a copy after join alias flattening. These items are skipped in the
equal() loop, so the same value elsewhere stays a constant. Param
takes the same path as Const, since the existing code accepts the two
together.
select 1 as one group by rollup(one) order by one nulls first still
returns a null row and then 1.
select 1 as one, 1+2 as three group by rollup(one) leaves three as 3.
The reported query no longer crashes.
GROUP BY true identified the boolean constant, and the true inside
ArrayCoerceExpr.elemexpr was a different Const.
Patch attached.
-- Regards,
Rachitskiy Andrey
