Add missing API method in prometheus table

Signed-off-by: Chen Dai <[email protected]>

prometheus/src/main/java/org/opensearch/sql/prometheus/storage/PrometheusMetricTable.java

@@ -58,6 +58,18 @@ public PrometheusMetricTable(PrometheusClient prometheusService,
     this.prometheusQueryRequest = Optional.of(prometheusQueryRequest);
   }
 
+  @Override
+  public boolean exists() {
+    throw new UnsupportedOperationException(
+        "Prometheus metric exists operation is not supported");
+  }
+
+  @Override
+  public void create(Map<String, ExprType> schema) {
+    throw new UnsupportedOperationException(
+        "Prometheus metric create operation is not supported");
+  }
+
   @Override
   public Map<String, ExprType> getFieldTypes() {
     if (cachedFieldTypes == null) {

prometheus/src/test/java/org/opensearch/sql/prometheus/storage/PrometheusMetricTableTest.java

@@ -7,6 +7,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
@@ -19,6 +20,7 @@
 import static org.opensearch.sql.prometheus.data.constants.PrometheusFieldConstants.VALUE;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -125,4 +127,14 @@ void testOptimize() {
     assertEquals(inputPlan, optimizedPlan);
   }
 
+  @Test
+  void testUnsupportedOperation() {
+    PrometheusQueryRequest prometheusQueryRequest = new PrometheusQueryRequest();
+    PrometheusMetricTable prometheusMetricTable =
+        new PrometheusMetricTable(client, prometheusQueryRequest);
+
+    assertThrows(UnsupportedOperationException.class, prometheusMetricTable::exists);
+    assertThrows(UnsupportedOperationException.class,
+        () -> prometheusMetricTable.create(Collections.emptyMap()));
+  }
 }