mattharder91 commented on code in PR #346:
URL: https://github.com/apache/datafusion-comet/pull/346#discussion_r1589454356
##########
core/src/execution/datafusion/expressions/cast.rs:
##########
@@ -107,6 +108,72 @@ macro_rules! cast_utf8_to_timestamp {
}};
}
+macro_rules! cast_float_to_string {
+ ($from:expr, $eval_mode:expr, $type:ty, $output_type:ty, $offset_type:ty)
=> {{
+
+ fn cast<OffsetSize>(
+ from: &dyn Array,
+ _eval_mode: EvalMode,
+ ) -> CometResult<ArrayRef>
+ where
+ OffsetSize: OffsetSizeTrait, {
+ let array =
from.as_any().downcast_ref::<$output_type>().unwrap();
+
+ // If the absolute number is less than 10,000,000 and greater
or equal than 0.001, the
+ // result is expressed without scientific notation with at
least one digit on either side of
+ // the decimal point. Otherwise, Spark uses a mantissa
followed by E and an
+ // exponent. The mantissa has an optional leading minus sign
followed by one digit to the
+ // left of the decimal point, and the minimal number of digits
greater than zero to the
+ // right. The exponent has and optional leading minus sign.
+ // source:
https://docs.databricks.com/en/sql/language-manual/functions/cast.html
+
+ const LOWER_SCIENTIFIC_BOUND: $type = 0.001;
+ const UPPER_SCIENTIFIC_BOUND: $type = 10000000.0;
+
+ let output_array = array
+ .iter()
+ .map(|value| match value {
+ Some(value) if value == <$type>::INFINITY =>
Ok(Some("Infinity".to_string())),
+ Some(value) if value == <$type>::NEG_INFINITY =>
Ok(Some("-Infinity".to_string())),
+ Some(value)
+ if (value.abs() < UPPER_SCIENTIFIC_BOUND
+ && value.abs() >= LOWER_SCIENTIFIC_BOUND)
+ || value.abs() == 0.0 =>
+ {
+ let trailing_zero = if value.fract() == 0.0 { ".0"
} else { "" };
+
+ Ok(Some(format!("{value}{trailing_zero}")))
+ }
+ Some(value)
+ if value.abs() >= UPPER_SCIENTIFIC_BOUND
+ || value.abs() < LOWER_SCIENTIFIC_BOUND =>
+ {
+ let formatted = format!("{value:E}");
+
+ if formatted.contains(".") {
+ Ok(Some(formatted))
+ } else {
+ let prepare_number: Vec<&str> =
formatted.split("E").collect();
Review Comment:
Done
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