suxiaogang223 commented on code in PR #65262:
URL: https://github.com/apache/doris/pull/65262#discussion_r3584000860
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fe/be-java-extensions/iceberg-metadata-scanner/src/main/java/org/apache/doris/iceberg/IcebergSysTableJniScanner.java:
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@@ -106,9 +103,10 @@ protected int getNext() throws IOException {
break;
}
StructLike row = reader.next();
- for (int i = 0; i < fields.size(); i++) {
- SelectedField field = fields.get(i);
- Object value = row.get(field.sourceIndex,
field.field.type().typeId().javaClass());
+ for (int i = 0; i < requiredFieldCount; i++) {
+ // FE keeps the fields requested by BE at the start of the
Iceberg projection.
+ // FileScanTask.schema() is not the row schema for every
DataTask implementation.
+ Object value = row.get(i, Object.class);
ColumnValue columnValue = new
IcebergSysTableColumnValue(value, timezone);
Review Comment:
Thanks for tracing the hypothetical zero-column JNI path. That path is not
reachable for the current scan plan, though:
`PhysicalPlanTranslator.updateScanSlotsMaterialization()` explicitly keeps the
smallest physical scan slot when projection would otherwise remove every slot,
and a storage-layer COUNT without a project retains the underlying relation
output. As a result, `file_slot_descs`/`required_fields` remain non-empty
before split planning, and `IcebergSysTableJniScanner` appends that retained
field for each row. The existing FE behavior is therefore already the "keep a
cheap required output field" option suggested here.
I agree that the two COUNT regression statements currently verify execution
only, not the returned value. That is useful test hardening, but it does not
make the zero-column path reachable or require BE virtual-row propagation for
this PR.
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