kumarUjjawal commented on code in PR #25956:
URL: https://github.com/apache/datafusion/pull/25956#discussion_r4163107479
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datafusion/expr/src/logical_plan/builder.rs:
##########
@@ -88,6 +90,93 @@ impl LogicalPlanBuilderOptions {
}
}
+fn recursive_type_can_be_coerced(from: &DataType, into: &DataType) -> bool {
+ if from == into || *from == DataType::Null {
+ return true;
+ }
+ // Preserve the integer coercion supported by recursive queries since
#9794.
+ if from.is_integer() && into.is_integer() {
+ return true;
+ }
+ if matches!(
+ (from, into),
+ (DataType::Date32, DataType::Date64)
+ | (DataType::Utf8, DataType::LargeUtf8 | DataType::Utf8View)
+ | (DataType::LargeUtf8, DataType::Utf8View)
+ | (
+ DataType::Binary,
+ DataType::LargeBinary | DataType::BinaryView
+ )
+ | (DataType::LargeBinary, DataType::BinaryView)
+ | (
+ DataType::FixedSizeBinary(_),
+ DataType::Binary | DataType::BinaryView
+ )
+ ) {
+ return true;
+ }
+ // Compound types and changes of type category need an explicit seed type.
+ // UNION's common-type rules can hide lossy casts within nested fields.
+ if !from.is_numeric() || !into.is_numeric() {
+ return false;
+ }
+ if type_union_coercion(into, from).as_ref() != Some(into) {
+ return false;
+ }
Review Comment:
**Medium ยท Apply decimal range checks before the UNION-type gate**
For an `Int64` recursive column and a `DECIMAL(19,0)` seed, this gate
rejects a lossless conversion: `type_union_coercion` represents signed and
unsigned 64-bit integers as `Decimal128(20,0)`, although every signed `Int64`
fits in 19 digits. Consequently, `WITH RECURSIVE t AS (SELECT 1::DECIMAL(19,0)
AS a UNION ALL SELECT 2::BIGINT FROM t WHERE a < 2) SELECT * FROM t` now fails
planning. The more accurate signed-integer range check below is never reached.
Handle decimal destinations with that range/scale check before requiring
equality with UNION's common type.
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