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Fix union equivalence schema rewrite with stale constants #23375

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Merged
xudong963 merged 1 commit into from
Jul 9, 2026
Merged

Fix union equivalence schema rewrite with stale constants #23375

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13 changes: 12 additions & 1 deletion datafusion/physical-expr/src/equivalence/properties/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1314,7 +1314,18 @@ impl EquivalenceProperties {
if let (Some(data_type), Some(AcrossPartitions::Uniform(Some(value)))) =
(data_type, &mut eq_class.constant)
{
*value = value.cast_to(&data_type)?;
match value.cast_to(&data_type) {
Ok(cast_value) => *value = cast_value,
Err(_) => {
// This is optimizer metadata. If a stale constant
// value cannot be represented after schema rewrite,
// drop the constant instead of failing planning.
eq_class.constant = None;
}
}
}
if eq_class.is_trivial() {
continue;
}
eq_classes.push(eq_class);
}
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32 changes: 31 additions & 1 deletion datafusion/physical-expr/src/equivalence/properties/union.rs
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Expand Up @@ -311,7 +311,7 @@ mod tests {
use crate::equivalence::tests::{create_test_schema, parse_sort_expr};
use crate::expressions::col;

use arrow::datatypes::{DataType, Field, Schema};
use arrow::datatypes::{DataType, Field, Schema, TimeUnit};
use datafusion_common::ScalarValue;

use itertools::Itertools;
Expand Down Expand Up @@ -899,6 +899,36 @@ mod tests {
Ok(())
}

#[test]
fn test_union_drops_unrepresentable_constant_value_after_schema_rewrite() -> Result<()>

@kosiew kosiew Jul 9, 2026

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Nice targeted test for the stale metadata state. As a follow-up, it may be worth adding a higher-level regression test that builds the filter/projection/union plan shape from the original issue and checks that UnionExec::try_new or physical planning succeeds. That would help protect the full path that produced the stale constant, not just the calculate_union boundary.

@xudong963 xudong963 Jul 9, 2026

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Thanks, that makes sense. The current test intentionally targets the exact stale-metadata boundary in calculate_union. I agree a higher-level regression would be useful, especially if we can capture the original filter/projection/union shape reliably. Since the reduced issue does not include a concrete SQL repro and the normal projection path should drop removed-column constants, I’ll keep this PR focused and consider adding a UnionExec::try_new/planner-level regression as a follow-up.

{
let input_schema = Arc::new(Schema::new(vec![Field::new(
"ticker",
DataType::Timestamp(TimeUnit::Nanosecond, None),
true,
)]));
let output_schema = Arc::new(Schema::new(vec![Field::new(
"timestamp",
DataType::Timestamp(TimeUnit::Nanosecond, None),
true,
)]));

let ticker = col("ticker", &input_schema)?;
let stale_value = ScalarValue::Utf8(Some("ESU6".to_owned()));
let const_expr = ConstExpr::new(
Arc::clone(&ticker),
AcrossPartitions::Uniform(Some(stale_value)),
);

let mut input = EquivalenceProperties::new(input_schema);
input.add_constants(vec![const_expr])?;

let union_props = calculate_union(vec![input], output_schema)?;
assert!(union_props.constants().is_empty());

Ok(())
}

/// Return a new schema with the same types, but new field names
///
/// The new field names are the old field names with `text` appended.
Expand Down
4 changes: 1 addition & 3 deletions datafusion/physical-plan/src/union.rs
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Expand Up @@ -130,9 +130,7 @@ impl UnionExec {
// The schema of the inputs and the union schema is consistent when:
// - They have the same number of fields, and
// - Their fields have same types at the same indices.
// Here, we know that schemas are consistent and the call below can
// not return an error.
let cache = Self::compute_properties(&inputs, schema).unwrap();
let cache = Self::compute_properties(&inputs, schema)?;
Ok(Arc::new(UnionExec {
inputs,
metrics: ExecutionPlanMetricsSet::new(),
Expand Down
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