[SPARK-29444] change ignoreNullFields doc

Author: stczwd

python/pyspark/sql/readwriter.py

@@ -817,9 +817,8 @@ def json(self, path, mode=None, compression=None, dateFormat=None, timestampForm
                         the default UTF-8 charset will be used.
         :param lineSep: defines the line separator that should be used for writing. If None is
                         set, it uses the default value, ``\\n``.
-        :param ignoreNullFields: whether to ignore null fields in column/struct
-                        during json generating. If None is set,
-                        it uses the default value, ``true``.
+        :param ignoreNullFields: Whether to ignore null fields when generating JSON objects.
+                        If None is set, it uses the default value, ``true``.
 
         >>> df.write.json(os.path.join(tempfile.mkdtemp(), 'data'))
         """

sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala

@@ -1189,8 +1189,9 @@ object SQLConf {
 
   val JSON_GENERATOR_IGNORE_NULL_FIELDS =
     buildConf("spark.sql.jsonGenerator.ignoreNullFields")
-      .doc("Whether to ignore null fields in column/struct during json generating. " +
-        "If false, json generator will generate null in Column/Struct.")
+      .doc("Whether to ignore null fields when generating JSON objects in JSON data source and " +
+        "JSON functions such as to_json. " +
+        "If false, it generates null for null fields in JSON objects.")
       .booleanConf
       .createWithDefault(true)
 

sql/core/src/main/scala/org/apache/spark/sql/DataFrameWriter.scala

@@ -687,8 +687,8 @@ final class DataFrameWriter[T] private[sql](ds: Dataset[T]) {
    * <li>`encoding` (by default it is not set): specifies encoding (charset) of saved json
    * files. If it is not set, the UTF-8 charset will be used. </li>
    * <li>`lineSep` (default `\n`): defines the line separator that should be used for writing.</li>
-   * <li>`ignoreNullFields` (default `true`): whether to ignore null fields in column/struct
-   * during json generating. </li>
+   * <li>`ignoreNullFields` (default `true`): Whether to ignore null fields
+   * when generating JSON objects. </li>
    * </ul>
    *
    * @since 1.4.0