test(expression): Add repeat function test

Author: Standing-Man

src/array/ops.rs

@@ -643,16 +643,13 @@ impl ArrayImpl {
                 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)
-            },
-        )))
+        Ok(A::new_string(binary_op(a.as_ref(), b.as_ref(), |a, b| {
+            let mut res = String::new();
+            for _ in 0..(*b) {
+                res += a;
+            }
+            res
+        })))
     }
 
     pub fn vector_l2_distance(&self, other: &ArrayImpl) -> Result {

tests/sql/repeat.slt

@@ -0,0 +1,34 @@
+query I
+select repeat('abc', 3);
+----
+abcabcabc
+
+statement ok
+create table t(v varchar(20));
+
+statement ok
+insert into t values ('test1'), ('test2'), ('test3'), ('test4'), ('test5'), ('test6'), ('test7'), ('test8');
+
+query I
+select repeat(v, 2) from t;
+----
+test1test1
+test2test2
+test3test3
+test4test4
+test5test5
+test6test6
+test7test7
+test8test8
+
+query I
+select repeat(v, -1) from t;
+----
+(empty)
+(empty)
+(empty)
+(empty)
+(empty)
+(empty)
+(empty)
+(empty)