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

[via GitHub]

WweiL commented on code in PR #41026:
URL: https://github.com/apache/spark/pull/41026#discussion_r1195753208


##########
sql/core/src/main/scala/org/apache/spark/sql/streaming/DataStreamWriter.scala:
##########
@@ -354,7 +355,8 @@ final class DataStreamWriter[T] private[sql](ds: 
Dataset[T]) {
       query
     } else if (source == SOURCE_NAME_FOREACH) {
       assertNotPartitioned(SOURCE_NAME_FOREACH)
-      val sink = ForeachWriterTable[T](foreachWriter, ds.exprEnc)
+      val sink = ForeachWriterTable[Any](foreachWriter,
+        ds.exprEnc.asInstanceOf[ExpressionEncoder[Any]])

Review Comment:
   I tried making 
   ` private var foreachWriter: ForeachWriter[_] = null`
   
   Then here if I do
   ```
   val sink = ForeachWriterTable[_](foreachWriter, ds.exprEnc)
   ```
   I get:
   ```
   [error] 
/home/wei.liu/oss-spark/sql/core/src/main/scala/org/apache/spark/sql/streaming/DataStreamWriter.scala:358:37:
 unbound wildcard type
   [error]       val sink = ForeachWriterTable[_](foreachWriter, ds.exprEnc)
   [error]                                     ^
   [error] one error found
   ```
   
   If I do 
   ```
   val sink = ForeachWriterTable[Any](foreachWriter, ds.exprEnc)
   ```
   I get:
   ```
   [error] 
/home/wei.liu/oss-spark/sql/core/src/main/scala/org/apache/spark/sql/streaming/DataStreamWriter.scala:358:36:
 overloaded method value apply with alternatives:
   [error]   (writer: org.apache.spark.sql.ForeachWriter[Any],converter: 
Either[org.apache.spark.sql.catalyst.encoders.ExpressionEncoder[Any],org.apache.spark.sql.catalyst.InternalRow
 => 
Any])org.apache.spark.sql.execution.streaming.sources.ForeachWriterTable[Any] 
<and>
   [error]   (writer: org.apache.spark.sql.ForeachWriter[Any],encoder: 
org.apache.spark.sql.catalyst.encoders.ExpressionEncoder[Any])org.apache.spark.sql.execution.streaming.sources.ForeachWriterTable[_]
   [error]  cannot be applied to (org.apache.spark.sql.ForeachWriter[_$2], 
org.apache.spark.sql.catalyst.encoders.ExpressionEncoder[T])
   [error]       val sink = ForeachWriterTable[Any](foreachWriter, ds.exprEnc)
   [error]                                    ^
   [error] one error found
   ```



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