fix: borrow decimal values in SQL tests

Decimal formatting only borrows its input. Preserve that ownership
contract to satisfy all-feature Clippy checks.

Author: Phoenix500526

datafusion/sqllogictest/src/engines/conversion.rs

@@ -96,7 +96,7 @@ pub(crate) fn arrow_decimal_to_str<T: DecimalType>(
 }
 
 #[cfg(feature = "postgres")]
-pub(crate) fn decimal_to_str(value: BigDecimal) -> String {
+pub(crate) fn decimal_to_str(value: &BigDecimal) -> String {
     value.to_plain_string()
 }
 

datafusion/sqllogictest/src/engines/postgres_engine/mod.rs

@@ -377,7 +377,7 @@ fn cell_to_string(row: &SimpleQueryRow, column_type: &Type, idx: usize) -> Strin
         (&Type::INT4, Some(value)) => value.parse::<i32>().unwrap().to_string(),
         (&Type::INT8, Some(value)) => value.parse::<i64>().unwrap().to_string(),
         (&Type::NUMERIC, Some(value)) => {
-            decimal_to_str(BigDecimal::from_str(value).unwrap())
+            decimal_to_str(&BigDecimal::from_str(value).unwrap())
         }
         // Parse date/time strings explicitly to avoid locale-specific formatting.
         (&Type::DATE, Some(value)) => NaiveDate::parse_from_str(value, "%Y-%m-%d")