Support non-integer bases in decimal log and handle large Decimal256 values

Author: Yuvraj-cyborg

datafusion/functions/src/math/log.rs

@@ -125,8 +125,8 @@ where
     {
         return if unscaled > 0 {
             Ok(unscaled.ilog(base as u128) as f64)
-        } else {
-            Ok(f64::NAN)
+    } else {
+        Ok(f64::NAN)
         };
     }
 
@@ -1192,7 +1192,7 @@ mod tests {
                 assert!(
                     log_result.is_finite() && log_result > 0.0,
                     "Expected positive finite log result, got {log_result}"
-                );
+        );
             }
             ColumnarValue::Scalar(_) => {
                 panic!("Expected an array value")

datafusion/sqllogictest/test_files/decimal.slt

@@ -861,9 +861,11 @@ select log(100000000000000000000000000000000000::decimal(76,0));
 ----
 35
 
-# log(10^50) for decimal256 for a value larger than i128
-query error Arrow error: Not yet implemented: Log of Decimal256 larger than Decimal128 is not yet supported
+# log(10^50) for decimal256 for a value larger than i128 (uses f64 fallback)
+query R
 select log(100000000000000000000000000000000000000000000000000::decimal(76,0));
+----
+50
 
 # log(10^35) for decimal128 with explicit base
 query R