fix: decimal256 display missing zeros

bindings/python/src/lib.rs

@@ -138,10 +138,7 @@ impl Row {
     pub fn values<'p>(&'p self, py: Python<'p>) -> PyResult<PyObject> {
         let res = PyTuple::new(
             py,
-            self.0
-                .values()
-                .into_iter()
-                .map(|v| Value(v.clone()).into_py(py)), // FIXME: do not clone
+            self.0.values().iter().map(|v| Value(v.clone()).into_py(py)), // FIXME: do not clone
         );
         Ok(res.into_py(py))
     }
@@ -232,7 +229,7 @@ impl RowIterator {
     fn __aiter__(slf: PyRef<'_, Self>) -> PyRef<'_, Self> {
         slf
     }
-    fn __anext__<'a>(&self, py: Python<'a>) -> PyResult<Option<PyObject>> {
+    fn __anext__(&self, py: Python<'_>) -> PyResult<Option<PyObject>> {
         let streamer = self.0.clone();
         let future = future_into_py(py, async move {
             match streamer.lock().await.next().await {

cli/tests/00-base.result

@@ -6,7 +6,7 @@ a	1	true	[1,2]
 3
 []	{}
 with comment
-3.00	3.00
+3.00	3.00	0.0000000170141183460469231731687303715884105727000	-0.0000000170141183460469231731687303715884105727000
 Asia/Shanghai
 0	0.00
 1	1.00

cli/tests/00-base.sql

@@ -20,7 +20,7 @@ select /* ignore this block */ 'with comment';
 select 'in comment block';
 */
 
-select 1.00 + 2.00, 3.00;
+select 1.00 + 2.00, 3.00, 0.0000000170141183460469231731687303715884105727000, -0.0000000170141183460469231731687303715884105727000;
 
 select/*+ SET_VAR(timezone='Asia/Shanghai') */ timezone();
 

sql/src/value.rs

@@ -700,25 +700,46 @@ pub fn display_decimal_256(num: i256, scale: u8) -> String {
         write!(buf, "{}", num).unwrap();
     } else {
         let pow_scale = i256::from_i128(10i128).pow_wrapping(scale as u32);
+        let width = scale as usize;
         // -1/10 = 0
-        if num >= i256::ZERO {
-            write!(
-                buf,
-                "{}.{:0>width$}",
-                num / pow_scale,
-                (num % pow_scale).wrapping_abs(),
-                width = scale as usize
-            )
-            .unwrap();
+        let (int_part, neg) = if num >= i256::ZERO {
+            (num / pow_scale, "")
         } else {
-            write!(
-                buf,
-                "-{}.{:0>width$}",
-                -num / pow_scale,
-                (num % pow_scale).wrapping_abs(),
-                width = scale as usize
-            )
-            .unwrap();
+            (-num / pow_scale, "-")
+        };
+        let frac_part = (num % pow_scale).wrapping_abs();
+
+        match frac_part.to_i128() {
+            Some(frac_part) => {
+                write!(
+                    buf,
+                    "{}{}.{:0>width$}",
+                    neg,
+                    int_part,
+                    frac_part,
+                    width = width
+                )
+                .unwrap();
+            }
+            None => {
+                // fractional part is too big for display,
+                // split it into two parts.
+                let pow = i256::from_i128(10i128).pow_wrapping(38);
+                let frac_high_part = frac_part / pow;
+                let frac_low_part = frac_part % pow;
+                let frac_width = (scale - 38) as usize;
+
+                write!(
+                    buf,
+                    "{}{}.{:0>width$}{}",
+                    neg,
+                    int_part,
+                    frac_high_part.to_i128().unwrap(),
+                    frac_low_part.to_i128().unwrap(),
+                    width = frac_width
+                )
+                .unwrap();
+            }
         }
     }
     buf