Github user bdrillard commented on a diff in the pull request:
https://github.com/apache/spark/pull/18075#discussion_r121989572
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/ColumnarBatchScan.scala
---
@@ -93,7 +93,7 @@ private[sql] trait ColumnarBatchScan extends
CodegenSupport {
}
val nextBatch = ctx.freshName("nextBatch")
--- End diff --
I suppose it depends on which implementation we think is cleaner. The
freshName generated by the caller is typically used twice, once in the call to
`addNewFunction`, but also immediately in the function code as the method name.
If we use a name hint, we'd have to do a string `replace` inside
`addNewFunction` to update the placeholder method name with the freshname. So
it would seem either we keep
```
val nextBatch = ctx.freshName("nextBatch")
val nextBatchFuncName = ctx.addNewFunction(nextBatch,
s"""
|private void $nextBatch() throws java.io.IOException {
| long getBatchStart = System.nanoTime();
| if ($input.hasNext()) {
| $batch = ($columnarBatchClz)$input.next();
| $numOutputRows.add($batch.numRows());
| $idx = 0;
| ${columnAssigns.mkString("", "\n", "\n")}
| }
| $scanTimeTotalNs += System.nanoTime() - getBatchStart;
|}""".stripMargin)
```
or we have
```
val nextBatchHint = "nextBatch"
val nextBatch = ctx.addNewFunction(nextBatchHint,
s"""
|private void $nextBatchHint() throws java.io.IOException {
| long getBatchStart = System.nanoTime();
| if ($input.hasNext()) {
| $batch = ($columnarBatchClz)$input.next();
| $numOutputRows.add($batch.numRows());
| $idx = 0;
| ${columnAssigns.mkString("", "\n", "\n")}
| }
| $scanTimeTotalNs += System.nanoTime() - getBatchStart;
|}""".stripMargin)
```
where `addNewFunction` would do the proper replacement over the code for
the method with a freshname generated from "nextBatch" as a name hint.
Or in every instance, we just duplicate the string hint without creating a
variable for it in both the `addNewFunction` call and the method name:
```
val nextBatch = ctx.addNewFunction("nextBatch",
s"""
|private void nextBatch() throws java.io.IOException {
| long getBatchStart = System.nanoTime();
| if ($input.hasNext()) {
| $batch = ($columnarBatchClz)$input.next();
| $numOutputRows.add($batch.numRows());
| $idx = 0;
| ${columnAssigns.mkString("", "\n", "\n")}
| }
| $scanTimeTotalNs += System.nanoTime() - getBatchStart;
|}""".stripMargin)
```
Which would you prefer?
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