feat(expression): support repeat function

Signed-off-by: Alan Tang <jmtangcs@gmail.com>

Author: Standing-Man

src/array/ops.rs

@@ -635,6 +635,26 @@ impl ArrayImpl {
         Ok(A::new_string(unary_op(a.as_ref(), |s| s.replace(from, to))))
     }
 
+    pub fn repeat(&self, num: &Self) -> Result {
+        let (A::String(a), A::Int32(b)) = (self, num) else {
+            return Err(ConvertError::NoBinaryOp(
+                "repeat".into(),
+                self.type_string(),
+                num.type_string(),
+            ));
+        };
+        Ok(A::new_string(binary_op(
+            a.as_ref(),
+            b.as_ref(),
+            |a, b| {
+                if *b < 0 {
+                    return String::new();
+                }
+                a.repeat(*b as usize)
+            },
+        )))
+    }
+
     pub fn vector_l2_distance(&self, other: &ArrayImpl) -> Result {
         let ArrayImpl::Vector(a) = self else {
             return Err(ConvertError::NoBinaryOp(

src/binder/expr.rs

@@ -447,6 +447,7 @@ impl Binder {
             "first" => Node::First(args[0]),
             "last" => Node::Last(args[0]),
             "replace" => Node::Replace([args[0], args[1], args[2]]),
+            "repeat" => Node::Repeat([args[0], args[1]]),
             "row_number" => Node::RowNumber,
             name => todo!("Unsupported function: {}", name),
         };

src/executor/evaluator.rs

@@ -132,6 +132,11 @@ impl<'a> Evaluator<'a> {
                 };
                 a.replace(from, to)
             }
+            Repeat([str, num]) => {
+                let str = self.next(*str).eval(chunk)?;
+                let num = self.next(*num).eval(chunk)?;
+                str.repeat(&num)
+            }
             VectorL2Distance([a, b]) => {
                 let a = self.next(*a).eval(chunk)?;
                 let b = self.next(*b).eval(chunk)?;

src/planner/explain.rs

@@ -176,6 +176,13 @@ impl<'a> Explain<'a> {
                     ("to", self.expr(c).pretty()),
                 ],
             ),
+            Repeat([str, num]) => Pretty::childless_record(
+                "Repeat",
+                vec![
+                    ("str", self.expr(str).pretty()),
+                    ("num", self.expr(num).pretty()),
+                ],
+            ),
             Substring([str, start, len]) => Pretty::childless_record(
                 "Substring",
                 vec![

src/planner/mod.rs

@@ -67,6 +67,7 @@ define_language! {
         "extract" = Extract([Id; 2]),           // (extract field expr)
             Field(DateTimeField),
         "replace" = Replace([Id; 3]),           // (replace expr pattern replacement)
+        "repeat" = Repeat([Id; 2]),             // (repeat expr the specified number of times)
         "substring" = Substring([Id; 3]),       // (substring expr start length)
 
         // vector functions

src/planner/rules/type_.rs

@@ -132,7 +132,9 @@ pub fn analyze_type(
                     .then_some(DataType::String)
             })
         }
-
+        Repeat([str, num]) => merge(enode, [x(str)?, x(num)?], |[str, num]| {
+            (str == DataType::String && num == DataType::Int32).then_some(DataType::String)
+        }),
         // number agg
         Max(a) | Min(a) => x(a),
         Sum(a) => check(enode, x(a)?, |a| a.is_number()),