[GitHub] [spark] WweiL commented on a diff in pull request #41026: [SPARK-43132] [SS] [CONNECT] Add DataStreamWriter foreach() API

["WweiL (via GitHub)" <gi...@apache.org>]

WweiL commented on code in PR #41026:
URL: https://github.com/apache/spark/pull/41026#discussion_r1183993090


##########
connector/connect/client/jvm/src/test/scala/org/apache/spark/sql/connect/client/CheckConnectJvmClientCompatibility.scala:
##########
@@ -226,16 +226,9 @@ object CheckConnectJvmClientCompatibility {
 
       // TypedColumn
       ProblemFilters.exclude[Problem]("org.apache.spark.sql.TypedColumn.this"),
-
-      // DataStreamReader
-      ProblemFilters.exclude[Problem](
-        "org.apache.spark.sql.streaming.DataStreamReader.table" // TODO( SPARK-43144)
-      ),
-
       // DataStreamWriter
       ProblemFilters.exclude[Problem](
-        "org.apache.spark.sql.streaming.DataStreamWriter.foreach" // TODO(SPARK-43133)
-      ),
+        "org.apache.spark.sql.streaming.DataStreamWriter.foreachPython"),

Review Comment:
   Please see my change in core DataStreamWriter



##########
sql/core/src/main/scala/org/apache/spark/sql/streaming/DataStreamWriter.scala:
##########
@@ -352,10 +355,15 @@ final class DataStreamWriter[T] private[sql](ds: Dataset[T]) {
         catalogTable = catalogTable)
       resultDf.createOrReplaceTempView(query.name)
       query
-    } else if (source == SOURCE_NAME_FOREACH) {
+    } else if (source == SOURCE_NAME_FOREACH && foreachWriter != null) {
       assertNotPartitioned(SOURCE_NAME_FOREACH)
       val sink = ForeachWriterTable[T](foreachWriter, ds.exprEnc)
       startQuery(sink, extraOptions, catalogTable = catalogTable)
+    } else if (source == SOURCE_NAME_FOREACH) {
+      assertNotPartitioned(SOURCE_NAME_FOREACH)
+      val sink = new ForeachWriterTable[UnsafeRow](
+        pythonForeachWriter, Right((x: InternalRow) => x.asInstanceOf[UnsafeRow]))

Review Comment:
   A copy from 
   
   https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/sources/ForeachWriterTable.scala#L96-L108
   
   See my comment below



##########
sql/core/src/main/scala/org/apache/spark/sql/streaming/DataStreamWriter.scala:
##########
@@ -534,6 +552,8 @@ final class DataStreamWriter[T] private[sql](ds: Dataset[T]) {
 
   private var foreachWriter: ForeachWriter[T] = null
 
+  private var pythonForeachWriter: PythonForeachWriter = null
+

Review Comment:
   I definitely think a discussion is needed here. The reason why I add this is because `foreachWriter` cannot be used here because it's type parameter is the same as the DataStreamWriter's, which is `Row`. But `PythonForeachWriter` extends ForeachWriter[UnsafeRow]:
   
   https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/python/PythonForeachWriter.scala#L33-L34
   
   Therefore I can't just create a `PythonForeachWriter` and call `writer.foreach(pythonForeachWriter)` in `SparkConnectPlanner`.
   
   The original caller is in python:
   https://github.com/apache/spark/blob/master/python/pyspark/sql/streaming/readwriter.py#L1309C24-L1315
   
   Maybe that circumvent this check somehow, I'm also very interested if anyone knows why is that



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