[GitHub] [spark] ueshin commented on a change in pull request #26512: [WIP][SPARK-29493][SQL] Arrow MapType support

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

ueshin commented on a change in pull request #26512: [WIP][SPARK-29493][SQL] Arrow MapType support
URL: https://github.com/apache/spark/pull/26512#discussion_r354576026
 
 

 ##########
 File path: sql/core/src/main/scala/org/apache/spark/sql/execution/arrow/ArrowWriter.scala
 ##########
 @@ -343,3 +348,37 @@ private[arrow] class StructWriter(
     children.foreach(_.reset())
   }
 }
+
+private[arrow] class MapWriter(
+    val valueVector: MapVector,
+    val keyWriter: ArrowFieldWriter,
+    val valueWriter: ArrowFieldWriter) extends ArrowFieldWriter {
+
+  override def setNull(): Unit = {}
+
+  override def setValue(input: SpecializedGetters, ordinal: Int): Unit = {
+    val map = input.getMap(ordinal)
+    valueVector.startNewValue(count)
+    val keys = map.keyArray()
+    val values = map.valueArray()
+
+    for (i <- 0 until map.numElements()) {
+      keyWriter.write(keys, i)
+      valueWriter.write(values, i)
+    }
 
 Review comment:
   We might want to use `while` loop to be performant like `ArrayWriter`.

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