explain getOffset

sql/core/src/main/java/org/apache/spark/sql/sources/v2/MicroBatchReadSupport.java

@@ -22,5 +22,8 @@ public interface MicroBatchReadSupport extends DataSourceV2 {
    * @param options the options for the returned data source reader, which is an immutable
    *                case-insensitive string-to-string map.
    */
-  MicroBatchReader createMicroBatchReader(Optional<StructType> schema, String checkpointLocation, DataSourceV2Options options);
+  MicroBatchReader createMicroBatchReader(
+      Optional<StructType> schema,
+      String checkpointLocation,
+      DataSourceV2Options options);
 }

sql/core/src/main/java/org/apache/spark/sql/sources/v2/reader/ContinuousDataReader.java

@@ -8,22 +8,12 @@
  * A variation on {@link DataReader} for use with streaming in continuous processing mode.
  */
 public interface ContinuousDataReader<T> extends DataReader<T> {
-    /**
-     * Proceed to next record, returning false only if the read is interrupted.
-     *
-     * @throws IOException if failure happens during disk/network IO like reading files.
-     */
-    boolean next() throws IOException;
-
-    /**
-     * Return the current record. This method should return same value until `next` is called.
-     */
-    T get();
-
     /**
      * Get the offset of the current record.
      *
-     * The execution engine will use this offset as a restart checkpoint.
+     * The execution engine will call this method along with get() to keep track of the current
+     * offset. When an epoch ends, the offset of the previous record in each partition will be saved
+     * as a restart checkpoint.
      */
     PartitionOffset getOffset();
 }