0lai0 commented on code in PR #5051:
URL: https://github.com/apache/datafusion-comet/pull/5051#discussion_r3690964474
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spark/src/main/scala/org/apache/spark/sql/comet/execution/arrow/CometArrowConverters.scala:
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@@ -74,4 +76,52 @@ object CometArrowConverters extends Logging {
}
}
}
+
+ /**
+ * Copy `numRows` rows starting at `startRow` from a Spark `ColumnarBatch`
into `root`.
+ *
+ * Spark's `ColumnVector` implementations do not expose Arrow buffers, so
values are necessarily
+ * copied element-wise. Shared by [[SparkColumnarArrowReader]], which slices
into a stable root,
+ * and [[columnarBatchToArrowBatch]], which fills a fresh one.
+ */
+ private[arrow] def writeColumns(
+ root: VectorSchemaRoot,
+ batch: ColumnarBatch,
+ startRow: Int,
+ numRows: Int): Unit = {
+ val writer = ArrowWriter.create(root)
+ var col = 0
+ while (col < batch.numCols()) {
+ val column = batch.column(col)
+ val columnArray = new ColumnarArray(column, startRow, numRows)
+ if (column.hasNull) {
+ writer.writeCol(columnArray, col)
+ } else {
+ writer.writeColNoNull(columnArray, col)
+ }
+ col += 1
+ }
+ writer.finish()
+ // ArrowWriter derives the root row count from its per-column writes, so a
zero-column input
+ // batch (Spark's count-from-metadata scan: numRows > 0, numCols == 0)
would otherwise produce
+ // a root with rowCount == 0 and silently drop the rows.
+ root.setRowCount(numRows)
+ }
+
+ /**
+ * Copy a Spark `ColumnarBatch` whose columns are not Arrow-backed (e.g.
+ * `On/OffHeapColumnVector` from Spark's vectorized Parquet reader, or a
third-party connector's
+ * vectors) into a freshly allocated Arrow `ColumnarBatch` of `CometVector`s.
+ *
+ * The input batch is not consumed or closed; the caller owns the returned
batch and must close
+ * it.
+ */
+ def columnarBatchToArrowBatch(
+ batch: ColumnarBatch,
+ arrowSchema: Schema,
+ allocator: BufferAllocator): ColumnarBatch = {
+ val root = VectorSchemaRoot.create(arrowSchema, allocator)
Review Comment:
Minor Nit: `columnarBatchToArrowBatch` allocates root before
`NativeUtil.rootAsBatch` wraps it.
If `writeColumns` or the wrap throws, root leaks, since the caller only
closes the returned batch.
Consider guarding the body with `try { ... } catch { case NonFatal(e) =>
root.close(); throw e }.
But normal path will not lead to
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