Register missing TAN function for analytics engine

core/src/main/java/org/opensearch/sql/expression/function/PPLFuncImpTable.java

@@ -238,6 +238,7 @@
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.SUM;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.SYSDATE;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.TAKE;
+import static org.opensearch.sql.expression.function.BuiltinFunctionName.TAN;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.TIME;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.TIMEDIFF;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.TIMESTAMP;
@@ -1080,6 +1081,7 @@ void populate() {
       registerOperator(SIGN, SqlStdOperatorTable.SIGN);
       registerOperator(SIGNUM, SqlStdOperatorTable.SIGN);
       registerOperator(SIN, SqlStdOperatorTable.SIN);
+      registerOperator(TAN, SqlStdOperatorTable.TAN);
       registerOperator(CBRT, SqlStdOperatorTable.CBRT);
 
       registerOperator(IFNULL, SqlStdOperatorTable.COALESCE);

docs/user/ppl/functions/math.md

@@ -1425,4 +1425,34 @@ fetched rows / total rows = 1/1
 | 2.0       |
 +-----------+
 ```
-
+
+## TAN
+
+**Usage**: `TAN(x)`
+
+Calculates the tangent of `x`, where `x` is given in radians.
+
+**Parameters**:
+
+- `x` (Required): An `INTEGER`, `LONG`, `FLOAT`, or `DOUBLE` value.
+
+**Return type**: `DOUBLE`
+
+### Example
+
+```ppl
+source=people
+| eval `TAN(0)` = TAN(0)
+| fields `TAN(0)`
+```
+
+The query returns the following results:
+
+```text
+fetched rows / total rows = 1/1
++--------+
+| TAN(0) |
+|--------|
+| 0.0    |
++--------+
+```

integ-test/src/test/java/org/opensearch/sql/calcite/remote/CalcitePPLBuiltinFunctionIT.java

@@ -192,6 +192,18 @@ public void testPiAndCot() throws IOException {
     verifyDataRows(actual, closeTo(1.0));
   }
 
+  @Test
+  public void testTan() throws IOException {
+    JSONObject actual =
+        executeQuery(
+            String.format(
+                "source=%s | eval tan = tan(pi() / 4) | head 1 | fields tan",
+                TEST_INDEX_STATE_COUNTRY));
+
+    verifySchema(actual, schema("tan", "double"));
+    verifyDataRows(actual, closeTo(1.0));
+  }
+
   @Test
   public void testCrc32AndAbs() throws IOException {
     JSONObject actual =

ppl/src/test/java/org/opensearch/sql/ppl/calcite/CalcitePPLMathFunctionTest.java

@@ -334,4 +334,11 @@ public void testSqrt() {
     String expectedSparkSql = "SELECT POWER(4, 5E-1) `SQRT`\nFROM `scott`.`EMP`";
     verifyPPLToSparkSQL(root, expectedSparkSql);
   }
+
+  @Test
+  public void testTan() {
+    withPPLQuery("source=EMP | eval TAN = tan(0) | fields TAN")
+        .expectLogical("LogicalProject(TAN=[TAN(0)])\n  LogicalTableScan(table=[[scott, EMP]])\n")
+        .expectSparkSQL("SELECT TAN(0) `TAN`\nFROM `scott`.`EMP`");
+  }
 }