huaxingao commented on code in PR #11551:
URL: https://github.com/apache/iceberg/pull/11551#discussion_r1847131830
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spark/v3.5/spark/src/main/java/org/apache/iceberg/spark/data/vectorized/ColumnarBatchReader.java:
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@@ -45,11 +45,23 @@ public class ColumnarBatchReader extends
BaseBatchReader<ColumnarBatch> {
private final boolean hasIsDeletedColumn;
private DeleteFilter<InternalRow> deletes = null;
private long rowStartPosInBatch = 0;
+ // In the case of Equality Delete, we have also built ColumnarBatchReader
for the equality delete
+ // filter columns to read the value to find out which rows are deleted. If
these deleted filter
+ // columns are not in the requested schema, then these are the extra columns
that we want to
+ // remove before return the ColumnBatch to Spark.
+ // Supposed table schema is C1, C2, C3, C4, C5, The query is:
+ // SELECT C5 FROM table, and the equality delete Filter is on C3, C4,
+ // We read the values of C3, C4 to figure out which rows are deleted, but we
don't want to include
+ // these values in the ColumnBatch that we return to Spark. In this example,
the numOfExtraColumns
+ // is 2. Since when creating the DeleteFilter, we append these extra columns
in the end of the
+ // requested schema, we can just remove them from the end of the
ColumnVector.
Review Comment:
Thanks for taking a look!
We traverse the schema and build a `VectorizedReader` for each of the column
in
[VectorizedReaderBuilder](https://github.com/apache/iceberg/blob/main/arrow/src/main/java/org/apache/iceberg/arrow/vectorized/VectorizedReaderBuilder.java#L71),
this is done before
DeleteFilte.[fileProjection](https://github.com/apache/iceberg/blob/06dc721498d6ad95c86f0f884b8ad30f807ef321/data/src/main/java/org/apache/iceberg/data/DeleteFilter.java#L306)
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