[GitHub] [spark] grundprinzip commented on a diff in pull request #38300: [SPARK-40854] [CONNECT] Use proper JSON encoding until we have Arrow collection.

[GitBox <gi...@apache.org>]

grundprinzip commented on code in PR #38300:
URL: https://github.com/apache/spark/pull/38300#discussion_r1000995568


##########
connector/connect/src/main/scala/org/apache/spark/sql/connect/service/SparkConnectStreamHandler.scala:
##########
@@ -59,19 +61,48 @@ class SparkConnectStreamHandler(responseObserver: StreamObserver[Response]) exte
 
   private def processRows(clientId: String, rows: DataFrame) = {
     val timeZoneId = SQLConf.get.sessionLocalTimeZone
-    val schema =
-      ByteString.copyFrom(ArrowUtils.toArrowSchema(rows.schema, timeZoneId).toByteArray)
-
-    val textSchema = rows.schema.fields.map(f => f.name).mkString("|")
-    val data = rows.collect().map(x => x.toSeq.mkString("|")).mkString("\n")
-    val bbb = proto.Response.CSVBatch.newBuilder
-      .setRowCount(-1)
-      .setData(textSchema ++ "\n" ++ data)
-      .build()
-    val response = proto.Response.newBuilder().setClientId(clientId).setCsvBatch(bbb).build()
 
-    // Send all the data
-    responseObserver.onNext(response)
+    // Only process up to 10MB of data.
+    val sb = new StringBuilder
+    var rowCount = 0
+    rows.toJSON
+      .collect()
+      .foreach(row => {
+        if (sb.size + row.size > MAX_BATCH_SIZE) {
+          val response = proto.Response.newBuilder().setClientId(clientId)
+          val batch = proto.Response.JSONBatch
+            .newBuilder()
+            .setData(ByteString.copyFromUtf8(sb.toString()))
+            .setRowCount(rowCount)
+            .build()
+          response.setJsonBatch(batch)
+          responseObserver.onNext(response.build())
+          // When the data is sent, we have to clear the batch data and reset the row count for
+          // this batch.
+          sb.clear()
+          rowCount = 0
+        } else {
+          // Make sure to put the newline delimiters only between items and not at the end.
+          if (rowCount > 0) {
+            sb.append("\n")

Review Comment:
   JSON cannot have `\n` without it being escaped, so using a plain newline should work.



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