[Doris On ES][Bug-Fix] Resolve NullPointerException when multi fields with text type

fe/fe-core/src/main/java/org/apache/doris/external/elasticsearch/MappingPhase.java

@@ -20,6 +20,7 @@
 import org.apache.doris.catalog.Column;
 import org.apache.doris.catalog.EsTable;
 
+import org.apache.commons.lang3.StringUtils;
 import org.json.JSONObject;
 
 import java.util.Iterator;
@@ -156,6 +157,9 @@ private void resolveDocValuesFields(SearchContext searchContext, JSONObject fiel
             }
             docValueField = colName;
         }
-        searchContext.docValueFieldsContext().put(colName, docValueField);
+        // docValueField Cannot be null
+        if (StringUtils.isNotEmpty(docValueField)) {
+            searchContext.docValueFieldsContext().put(colName, docValueField);
+        }
     }
 }

fe/fe-core/src/test/java/org/apache/doris/external/elasticsearch/MappingPhaseTest.java

@@ -32,6 +32,7 @@
 import mockit.Injectable;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 
 public class MappingPhaseTest extends EsTestCase {
 
@@ -102,4 +103,14 @@ public void testWorkFlow(@Injectable EsRestClient client) throws Exception{
         assertEquals("k2", searchContext1.docValueFieldsContext().get("k2"));
 
     }
-}
+
+    @Test
+    public void testMultTextFields() throws Exception {
+        MappingPhase mappingPhase = new MappingPhase(null);
+        EsTable esTableAfter7X = fakeEsTable("fake", "test", "_doc", columns);
+        SearchContext searchContext = new SearchContext(esTableAfter7X);
+        mappingPhase.resolveFields(searchContext, loadJsonFromFile("data/es/test_index_mapping_field_mult_analyzer.json"));
+        assertFalse(searchContext.docValueFieldsContext().containsKey("k3"));
+
+    }
+}

fe/fe-core/src/test/resources/data/es/test_index_mapping_field_mult_analyzer.json

@@ -0,0 +1,23 @@
+{
+  "test": {
+    "mappings": {
+      "properties": {
+        "k1": {
+          "type": "long"
+        },
+        "k2": {
+          "type": "keyword"
+        },
+        "k3": {
+          "type": "text",
+          "fields": {
+            "ik": {
+              "type": "text",
+              "analyzer": "ik_max_word"
+            }
+          }
+        }
+      }
+    }
+  }
+}