Fix SQL string replace function

core/src/main/java/org/polypheny/db/functions/Functions.java

@@ -1985,6 +1985,13 @@ public static String replace( String s, String search, String replacement ) {
         return s.replace( search, replacement );
     }
 
+    /**
+     * SQL {@code REPLACE(string, search, replacement)} function.
+     */
+    public static PolyString replace( PolyString s, PolyString search, PolyString replacement ) {
+        return PolyString.of( s.value.replace( search.value, replacement.value ) );
+    }
+
 
     /**
      * Helper for "array element reference". Caller has already ensured that array and index are not null. Index is 1-based, per SQL.

dbms/src/test/java/org/polypheny/db/sql/fun/StringFunctionsTest.java

@@ -86,6 +86,22 @@ public static void stop() throws SQLException {
 
     // --------------- Tests ---------------
 
+    @Test
+    public void stringReplaceTest() throws SQLException {
+        try ( TestHelper.JdbcConnection polyphenyDbConnection = new TestHelper.JdbcConnection( true ) ) {
+            Connection connection = polyphenyDbConnection.getConnection();
+            try ( Statement statement = connection.createStatement() ) {
+                List<Object[]> expectedResult = ImmutableList.of(
+                        new Object[]{"Hello"}
+                );
+                TestHelper.checkResultSet(
+                        statement.executeQuery( "SELECT replace('Hi', 'i', 'ello')" ),
+                        expectedResult,
+                        true );
+            }
+        }
+    }
+
 
     @Test
     public void concatenatesTwoString() throws SQLException {