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fix: [df52] timestamp nanos precision loss with nanosAsLong #3502

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Merged
comphead merged 1 commit into from
Feb 12, 2026
Merged

fix: [df52] timestamp nanos precision loss with nanosAsLong #3502

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15 changes: 11 additions & 4 deletions native/core/src/parquet/schema_adapter.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -302,23 +302,30 @@ impl SparkPhysicalExprAdapter {
let physical_type = cast.input_field().data_type();
let target_type = cast.target_field().data_type();

// For complex nested types (Struct, List, Map) and Timestamp timezone
// mismatches, use CometCastColumnExpr with spark_parquet_convert which
// handles field-name-based selection, reordering, nested type casting,
// and metadata-only timestamp timezone relabeling correctly.
// For complex nested types (Struct, List, Map), Timestamp timezone
// mismatches, and Timestamp→Int64 (nanosAsLong), use CometCastColumnExpr
// with spark_parquet_convert which handles field-name-based selection,
// reordering, nested type casting, metadata-only timestamp timezone
// relabeling, and raw value reinterpretation correctly.
//
// Timestamp mismatches (e.g., Timestamp(us, None) -> Timestamp(us, Some("UTC")))
// occur when INT96 Parquet timestamps are coerced to Timestamp(us, None) by
// DataFusion but the logical schema expects Timestamp(us, Some("UTC")).
// Using Spark's Cast here would incorrectly treat the None-timezone values as
// local time (TimestampNTZ) and apply a timezone conversion, but the values are
// already in UTC. spark_parquet_convert handles this as a metadata-only change.
//
// Timestamp→Int64 occurs when Spark's `nanosAsLong` config converts
// TIMESTAMP(NANOS) to LongType. Spark's Cast would divide by MICROS_PER_SECOND
// (assuming microseconds), but the values are nanoseconds. Arrow cast correctly
// reinterprets the raw i64 value without conversion.
if matches!(
(physical_type, target_type),
(DataType::Struct(_), DataType::Struct(_))
| (DataType::List(_), DataType::List(_))
| (DataType::Map(_, _), DataType::Map(_, _))
| (DataType::Timestamp(_, _), DataType::Timestamp(_, _))
| (DataType::Timestamp(_, _), DataType::Int64)
) {
let comet_cast: Arc<dyn PhysicalExpr> = Arc::new(
CometCastColumnExpr::new(
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