support rewriting of ::numeric cast (#33)

Author: samuelcolvin

src/rewrite.rs

@@ -34,7 +34,9 @@ fn optimise_json_get_cast(cast: &Cast) -> Option<Transformed<Expr>> {
     }
     let func = match &cast.data_type {
         DataType::Boolean => crate::json_get_bool::json_get_bool_udf(),
-        DataType::Float64 | DataType::Float32 => crate::json_get_float::json_get_float_udf(),
+        DataType::Float64 | DataType::Float32 | DataType::Decimal128(_, _) | DataType::Decimal256(_, _) => {
+            crate::json_get_float::json_get_float_udf()
+        }
         DataType::Int64 | DataType::Int32 => crate::json_get_int::json_get_int_udf(),
         DataType::Utf8 => crate::json_get_str::json_get_str_udf(),
         _ => return None,

tests/main.rs

@@ -277,6 +277,20 @@ async fn test_json_get_cast_float() {
     assert_eq!(display_val(batches).await, (DataType::Float64, "420.0".to_string()));
 }
 
+#[tokio::test]
+async fn test_json_get_cast_numeric() {
+    let sql = r#"select json_get('{"foo": 4.2e2}', 'foo')::numeric"#;
+    let batches = run_query(sql).await.unwrap();
+    assert_eq!(display_val(batches).await, (DataType::Float64, "420.0".to_string()));
+}
+
+#[tokio::test]
+async fn test_json_get_cast_numeric_equals() {
+    let sql = r#"select json_get('{"foo": 420}', 'foo')::numeric = 420"#;
+    let batches = run_query(sql).await.unwrap();
+    assert_eq!(display_val(batches).await, (DataType::Boolean, "true".to_string()));
+}
+
 #[tokio::test]
 async fn test_json_get_bool() {
     let batches = run_query("select json_get_bool('[true]', 0)").await.unwrap();
@@ -1101,7 +1115,7 @@ async fn test_arrow_scalar_union_is_null() {
 }
 
 #[tokio::test]
-async fn test_arrow_cast() {
+async fn test_long_arrow_cast() {
     let batches = run_query("select (json_data->>'foo')::int from other").await.unwrap();
 
     let expected = [
@@ -1116,3 +1130,9 @@ async fn test_arrow_cast() {
     ];
     assert_batches_eq!(expected, &batches);
 }
+
+async fn test_arrow_cast_numeric() {
+    let sql = r#"select ('{"foo": 420}'->'foo')::numeric = 420"#;
+    let batches = run_query(sql).await.unwrap();
+    assert_eq!(display_val(batches).await, (DataType::Boolean, "true".to_string()));
+}