chaoqin-li1123 commented on code in PR #45023:
URL: https://github.com/apache/spark/pull/45023#discussion_r1489903039
##########
python/pyspark/sql/datasource.py:
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@@ -298,6 +320,104 @@ def read(self, partition: InputPartition) ->
Iterator[Union[Tuple, Row]]:
...
+class DataSourceStreamReader(ABC):
+ """
+ A base class for streaming data source readers. Data source stream readers
are responsible
+ for outputting data from a streaming data source.
+
+ .. versionadded: 4.0.0
+ """
+
+ def initialOffset(self) -> dict:
+ """
+ Return the initial offset of the streaming data source.
+ A new streaming query starts reading data from the initial offset.
+ If Spark is restarting an existing query, it will restart from the
check-pointed offset
+ rather than the initial one.
+
+ Returns
+ -------
+ dict
+ A dict whose key and values are str type.
Review Comment:
The serialization is easy, but deserialization will be tricky. We don't have
runtime type information to deserialize a plain json text back to python
object.(because we don't even know what python type the json is serialized from
unless we keep extra type information in the json)
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