Add REVERSE function (gluesql#327)

jekalhong · Aug 26, 2021 · 23e0e87 · 23e0e87
1 parent b9d9d69
commit 23e0e87
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Showing 6 changed files with 50 additions and 0 deletions.
diff --git a/src/ast/function.rs b/src/ast/function.rs
@@ -70,6 +70,8 @@ pub enum Function {
     Ltrim { expr: Expr, chars: Option<Expr> },
     #[strum(to_string = "RTRIM")]
     Rtrim { expr: Expr, chars: Option<Expr> },
+    #[strum(to_string = "REVERSE")]
+    Reverse(Expr),
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]

diff --git a/src/executor/evaluate/mod.rs b/src/executor/evaluate/mod.rs
@@ -555,6 +555,13 @@ async fn evaluate_function<'a, T: 'static + Debug>(
             }
             .map(Evaluated::from)
         }
+        Function::Reverse(expr) => {
+            match eval_to_str(expr).await? {
+                Nullable::Value(v) => Ok(Value::Str(v.chars().rev().collect::<String>())),
+                Nullable::Null => Ok(Value::Null),
+            }
+        }
+        .map(Evaluated::from),
     }
 }
 

diff --git a/src/tests/function/mod.rs b/src/tests/function/mod.rs
@@ -11,6 +11,7 @@ pub mod ltrim_rtrim;
 pub mod math_function;
 pub mod pi;
 pub mod radians;
+pub mod reverse;
 pub mod round;
 pub mod sqrt_power;
 pub mod trim;

diff --git a/src/tests/function/reverse.rs b/src/tests/function/reverse.rs
@@ -0,0 +1,38 @@
+use crate::*;
+
+test_case!(reverse, async move {
+    let test_cases = vec![
+        ("CREATE TABLE Item (name TEXT)", Ok(Payload::Create)),
+        (
+            r#"INSERT INTO Item VALUES ("Let's meet")"#,
+            Ok(Payload::Insert(1)),
+        ),
+        (
+            "SELECT REVERSE(name) AS test FROM Item;",
+            Ok(select!(
+                "test"
+                Value::Str;
+                "teem s'teL".to_owned()
+            )),
+        ),
+        (
+            r#"SELECT REVERSE(1) AS test FROM Item"#,
+            Err(EvaluateError::FunctionRequiresStringValue("REVERSE".to_owned()).into()),
+        ),
+        (
+            "CREATE TABLE NullTest (name TEXT null)",
+            Ok(Payload::Create),
+        ),
+        (
+            r#"INSERT INTO NullTest VALUES (null)"#,
+            Ok(Payload::Insert(1)),
+        ),
+        (
+            r#"SELECT REVERSE(name) AS test FROM NullTest"#,
+            Ok(select_with_null!(test; Value::Null)),
+        ),
+    ];
+    for (sql, expected) in test_cases.into_iter() {
+        test!(expected, sql);
+    }
+});
diff --git a/src/tests/mod.rs b/src/tests/mod.rs
@@ -95,6 +95,7 @@ macro_rules! generate_tests {
         glue!(function_radians, function::radians::radians);
         glue!(function_degrees, function::degrees::degrees);
         glue!(function_pi, function::pi::pi);
+        glue!(function_reverse, function::reverse::reverse);
 
         #[cfg(feature = "index")]
         macro_rules! glue_index {

diff --git a/src/translate/function.rs b/src/translate/function.rs
@@ -217,6 +217,7 @@ pub fn translate_function(sql_function: &SqlFunction) -> Result<Expr> {
                 divisor,
             })))
         }
+        "REVERSE" => func_with_one_arg!(Function::Reverse),
         _ => Err(TranslateError::UnsupportedFunction(name).into()),
     }
 }