Github user liancheng commented on a diff in the pull request:
https://github.com/apache/spark/pull/1880#discussion_r16035082
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/columnar/InMemoryColumnarTableScan.scala
---
@@ -90,22 +101,31 @@ private[sql] case class InMemoryColumnarTableScan(
override def execute() = {
relation.cachedColumnBuffers.mapPartitions { iterator =>
- val columnBuffers = iterator.next()
- assert(!iterator.hasNext)
+ // Find the ordinals of the requested columns. If none are
requested, use the first.
+ val requestedColumns =
+ if (attributes.isEmpty) {
+ Seq(0)
--- End diff --
Maybe we can use the narrowest one instead of the 1st one by checking
default sizes of columns:
```scala
val narrowest = relation.output.indices.minBy { i =>
ColumnType(relation.output(i).dataType).defaultSize
}
Seq(narrowest)
```
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