petern48 commented on code in PR #17835:
URL: https://github.com/apache/datafusion/pull/17835#discussion_r2389665889
##########
datafusion/optimizer/src/simplify_expressions/expr_simplifier.rs:
##########
@@ -1436,33 +1436,59 @@ impl<S: SimplifyInfo> TreeNodeRewriter for
Simplifier<'_, S> {
// CASE WHEN true THEN A ... END --> A
// CASE WHEN X THEN A WHEN TRUE THEN B ... END --> CASE WHEN X
THEN A ELSE B END
+ // CASE WHEN false THEN A END --> NULL
+ // CASE WHEN false THEN A ELSE B END --> B
+ // CASE WHEN X THEN A WHEN false THEN B END --> CASE WHEN X THEN A
ELSE B END
Expr::Case(Case {
expr: None,
mut when_then_expr,
- else_expr: _,
+ mut else_expr,
// if let guard is not stabilized so we can't use it yet:
https://github.com/rust-lang/rust/issues/51114
// Once it's supported we can avoid searching through
when_then_expr twice in the below .any() and .position() calls
// }) if let Some(i) = when_then_expr.iter().position(|(when,
_)| is_true(when.as_ref())) => {
}) if when_then_expr
.iter()
- .any(|(when, _)| is_true(when.as_ref())) =>
+ .any(|(when, _)| is_true(when.as_ref()) ||
is_false(when.as_ref())) =>
{
- let i = when_then_expr
- .iter()
- .position(|(when, _)| is_true(when.as_ref()))
- .unwrap();
- let (_, then_) = when_then_expr.swap_remove(i);
- // CASE WHEN true THEN A ... END --> A
- if i == 0 {
- return Ok(Transformed::yes(*then_));
+ let mut remove_indices =
Vec::with_capacity(when_then_expr.len());
+ let out_type = info.get_data_type(&when_then_expr[0].1)?;
Review Comment:
Introducing this `get_data_type` call made some of the existing tests fail
because it was trying to get the data type of a column that didn't exist in the
schema. I updated the existing tests to use the actual column names e.g
(`col("c1")`, `col("c3")`) or string literals (e.g lit("a")) instead of the
invalid column names (e.g `col("a")`) hence why so many random changes in the
old tests. When I ran queries in the CLI, it seemed like Datafusion was
catching the invalid column names before it got to this code, so I think this
should be safe.
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