emecii commented on code in PR #25143:
URL: https://github.com/apache/datafusion/pull/25143#discussion_r3989414124
##########
datafusion/optimizer/src/simplify_expressions/expr_simplifier.rs:
##########
@@ -2432,6 +2436,26 @@ fn simplify_inlist_set_operation(
}))
}
+/// Conservatively checks the inputs whose evaluation can change when lowering
+/// CASE to AND/OR. [`Expr`] has no general fallibility analysis: only columns
and
+/// literals are admitted from conditional branches, including later WHEN
conditions.
+/// The first WHEN already runs on every row, but must not be volatile because
+/// the rewrite can evaluate it more than once.
+fn can_lower_case_to_boolean(
+ when_then_expr: &[(Box<Expr>, Box<Expr>)],
+ else_expr: Option<&Expr>,
+) -> bool {
+ let is_leaf = |expr: &Expr| matches!(expr, Expr::Column(_) |
Expr::Literal(..));
+ when_then_expr.iter().enumerate().all(|(i, (when, then))| {
+ is_leaf(then)
+ && if i == 0 {
+ !when.is_volatile()
Review Comment:
Fixed in 3d52a60d0. The guard now requires the first WHEN, every later WHEN,
and all branch outputs to be columns or literals. I added the CAST(s AS INT)
regression with identical false outputs and a unit case proving the CASE is
preserved.
##########
datafusion/optimizer/src/simplify_expressions/expr_simplifier.rs:
##########
@@ -2432,6 +2436,26 @@ fn simplify_inlist_set_operation(
}))
}
+/// Conservatively checks the inputs whose evaluation can change when lowering
+/// CASE to AND/OR. [`Expr`] has no general fallibility analysis: only columns
and
+/// literals are admitted from conditional branches, including later WHEN
conditions.
Review Comment:
Updated in 3d52a60d0. The invariant comment now explicitly states that all
WHEN conditions and branch outputs must be columns or literals.
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