add property mapping description (#148)

* add property mapping description

* add property mapping description

README.md

@@ -70,7 +70,9 @@ NebulaGraph Spark Connector support spark 2.2, 2.4 and 3.0.
      <version>2.1.1</version>
   </dependency>
   ```
-  
+
+  When writing, please ensure that the column name of the DataFrame as an attribute is consistent with the attribute name in NebulaGraph. If they are inconsistent, please use `DataFrame.withColumnRenamed` to rename the DataFrame column name first.
+
   Write DataFrame `INSERT` into NebulaGraph as Vertices:
   ```
     val config = NebulaConnectionConfig

README_CN.md

@@ -79,6 +79,8 @@ Nebula Spark Connector 支持 Spark 2.2， 2.4 和 3.x.
   </dependency>
   ```
 
+在做写入时, 请确保作为属性的DataFrame的列名是和NebulaGraph中的属性名是一致的，如果不一致，请先使用 `DataFrame.withColumnRenamed` 进行DataFrame列名的重命名。
+
 将 DataFrame 作为点 `INSERT` 写入 Nebula Graph :
 
   ```

example/src/main/scala/com/vesoft/nebula/examples/connector/NebulaSparkWriterExample.scala

@@ -95,6 +95,8 @@ object NebulaSparkWriterExample {
     */
   def writeVertex(spark: SparkSession): Unit = {
     val df = spark.read.json("vertex")
+    // if the column of df is name1, age, born, then we need to rename it to name first. Because the name of Nebula Property is name.
+    // df.withColumnRenamed("name1", "name")
     df.show()
 
     val config = getNebulaConnectionConfig()