add string function RIGHT

core/src/main/java/com/amazon/opendistroforelasticsearch/sql/expression/DSL.java

@@ -409,6 +409,10 @@ public FunctionExpression strcmp(Expression... expressions) {
     return function(BuiltinFunctionName.STRCMP, expressions);
   }
 
+  public FunctionExpression right(Expression... expressions) {
+    return function(BuiltinFunctionName.RIGHT, expressions);
+  }
+
   public FunctionExpression and(Expression... expressions) {
     return function(BuiltinFunctionName.AND, expressions);
   }

core/src/main/java/com/amazon/opendistroforelasticsearch/sql/expression/function/BuiltinFunctionName.java

@@ -131,6 +131,7 @@ public enum BuiltinFunctionName {
   CONCAT_WS(FunctionName.of("concat_ws")),
   LENGTH(FunctionName.of("length")),
   STRCMP(FunctionName.of("strcmp")),
+  RIGHT(FunctionName.of("right")),
 
   /**
    * NULL Test.

core/src/main/java/com/amazon/opendistroforelasticsearch/sql/expression/text/TextFunction.java

@@ -60,6 +60,7 @@ public void register(BuiltinFunctionRepository repository) {
     repository.register(concat_ws());
     repository.register(length());
     repository.register(strcmp());
+    repository.register(right());
   }
 
   /**
@@ -194,6 +195,16 @@ private FunctionResolver strcmp() {
             INTEGER, STRING, STRING));
   }
 
+  /**
+   * Returns the rightmost len characters from the string str, or NULL if any argument is NULL.
+   * Supports following signatures:
+   * (STRING, INTEGER) -> STRING
+   */
+  private FunctionResolver right() {
+    return define(BuiltinFunctionName.RIGHT.getName(),
+            impl(nullMissingHandling(TextFunction::exprRight), STRING, STRING, INTEGER));
+  }
+
   private static ExprValue exprSubstrStart(ExprValue exprValue, ExprValue start) {
     int startIdx = start.integerValue();
     if (startIdx == 0) {
@@ -225,5 +236,10 @@ private static ExprValue exprSubStr(String str, int start, int len) {
     }
     return new ExprStringValue(str.substring(start, start + len));
   }
+
+  private static ExprValue exprRight(ExprValue str, ExprValue len) {
+    return new ExprStringValue(str.stringValue().substring(
+            str.stringValue().length() - len.integerValue()));
+  }
 }
 

core/src/test/java/com/amazon/opendistroforelasticsearch/sql/expression/text/TextFunctionTest.java

@@ -25,6 +25,7 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.mockito.Mockito.when;
 
+import com.amazon.opendistroforelasticsearch.sql.data.model.ExprIntegerValue;
 import com.amazon.opendistroforelasticsearch.sql.data.model.ExprStringValue;
 import com.amazon.opendistroforelasticsearch.sql.data.model.ExprValue;
 import com.amazon.opendistroforelasticsearch.sql.expression.DSL;
@@ -296,6 +297,23 @@ void strcmp() {
     assertEquals(missingValue(), eval(dsl.strcmp(missingRef, nullRef)));
   }
 
+  @Test
+  void right() {
+    FunctionExpression expression = dsl.right(
+            DSL.literal(new ExprStringValue("foobarbar")),
+            DSL.literal(new ExprIntegerValue(4)));
+    assertEquals(STRING, expression.type());
+    assertEquals("rbar", eval(expression).stringValue());
+
+    when(nullRef.type()).thenReturn(STRING);
+    when(missingRef.type()).thenReturn(INTEGER);
+    assertEquals(missingValue(), eval(dsl.right(nullRef, missingRef)));
+    assertEquals(nullValue(), eval(dsl.right(nullRef, DSL.literal(new ExprIntegerValue(1)))));
+
+    when(nullRef.type()).thenReturn(INTEGER);
+    assertEquals(nullValue(), eval(dsl.right(DSL.literal(new ExprStringValue("value")), nullRef)));
+  }
+
   void testConcatString(List<String> strings) {
     String expected = null;
     if (strings.stream().noneMatch(Objects::isNull)) {

docs/experiment/ppl/functions/string.rst

@@ -150,6 +150,29 @@ Example::
     +---------------------+---------------------+
 
 
+RIGHT
+-----
+
+Description
+>>>>>>>>>>>
+
+Usage: right(str, len) returns the rightmost len characters from the string str, or NULL if any argument is NULL.
+
+Argument type: STRING, INTEGER
+
+Return type: STRING
+
+Example::
+
+    od> source=people | eval `RIGHT('helloworld', 5)` = RIGHT('helloworld', 5), `RIGHT('HELLOWORLD', 0)` = RIGHT('HELLOWORLD', 0) | fields `RIGHT('helloworld', 5)`, `RIGHT('HELLOWORLD', 0)`
+    fetched rows / total rows = 1/1
+    +--------------------------+--------------------------+
+    | RIGHT('helloworld', 5)   | RIGHT('HELLOWORLD', 0)   |
+    |--------------------------+--------------------------|
+    | world                    |                          |
+    +--------------------------+--------------------------+
+
+
 RTRIM
 -----
 

docs/user/dql/functions.rst

@@ -1760,9 +1760,21 @@ RIGHT
 Description
 >>>>>>>>>>>
 
-Specifications:
+Usage: right(str, len) returns the rightmost len characters from the string str, or NULL if any argument is NULL.
+
+Argument type: STRING, INTEGER
+
+Return type: STRING
 
-1. RIGHT(STRING T, INTEGER) -> T
+Example::
+
+    od> SELECT RIGHT('helloworld', 5), RIGHT('HELLOWORLD', 0)
+    fetched rows / total rows = 1/1
+    +--------------------------+--------------------------+
+    | RIGHT('helloworld', 5)   | RIGHT('HELLOWORLD', 0)   |
+    |--------------------------+--------------------------|
+    | world                    |                          |
+    +--------------------------+--------------------------+
 
 
 RTRIM

integ-test/src/test/java/com/amazon/opendistroforelasticsearch/sql/ppl/TextCommandIT.java

@@ -92,6 +92,11 @@ public void testTrim() throws IOException {
     verifyQuery("trim", "", "", "hello", "world", "helloworld");
   }
 
+  @Test
+  public void testRight() throws IOException {
+    verifyQuery("right", "", ", 3", "llo", "rld", "rld");
+  }
+
   @Test
   public void testRtrim() throws IOException {
     verifyQuery("rtrim", "", "", "hello", "world", "helloworld");

integ-test/src/test/java/com/amazon/opendistroforelasticsearch/sql/sql/TextFunctionIT.java

@@ -126,6 +126,11 @@ public void testStrcmp() throws IOException {
     verifyQuery("strcmp('hello', 'hello')", "integer", 0);
   }
 
+  @Test
+  public void testRight() throws IOException {
+    verifyQuery("right('variable', 4)", "keyword", "able");
+  }
+
   protected JSONObject executeQuery(String query) throws IOException {
     Request request = new Request("POST", QUERY_API_ENDPOINT);
     request.setJsonEntity(String.format(Locale.ROOT, "{\n" + "  \"query\": \"%s\"\n" + "}", query));

integ-test/src/test/resources/correctness/expressions/text_functions.txt

@@ -0,0 +1 @@
+RIGHT('Hello World', 5) as column

ppl/src/main/antlr/OpenDistroPPLLexer.g4

@@ -228,6 +228,7 @@ CONCAT:                             'CONCAT';
 CONCAT_WS:                          'CONCAT_WS';
 LENGTH:                             'LENGTH';
 STRCMP:                             'STRCMP';
+RIGHT:                              'RIGHT';
 
 // BOOL FUNCTIONS
 LIKE:                               'LIKE';

ppl/src/main/antlr/OpenDistroPPLParser.g4

@@ -258,6 +258,7 @@ conditionFunctionBase
 
 textFunctionBase
     : SUBSTR | SUBSTRING | TRIM | LTRIM | RTRIM | LOWER | UPPER | CONCAT | CONCAT_WS | LENGTH | STRCMP
+    | RIGHT
     ;
 
 /** operators */

sql/src/main/antlr/OpenDistroSQLParser.g4

@@ -345,7 +345,7 @@ dateTimeFunctionName
 
 textFunctionName
     : SUBSTR | SUBSTRING | TRIM | LTRIM | RTRIM | LOWER | UPPER
-    | CONCAT | CONCAT_WS | SUBSTR | LENGTH | STRCMP
+    | CONCAT | CONCAT_WS | SUBSTR | LENGTH | STRCMP | RIGHT
     ;
 
 functionArgs