milesgranger commented on code in PR #14326:
URL: https://github.com/apache/arrow/pull/14326#discussion_r997391097
##########
cpp/src/arrow/dataset/scanner_test.cc:
##########
@@ -1074,6 +1074,24 @@ TEST_P(TestScanner, ProjectedScanNested) {
AssertScanBatchesUnorderedEqualRepetitionsOf(MakeScanner(batch_in),
batch_out);
}
+TEST_P(TestScanner, ProjectedScanNestedFromNames) {
+ SetSchema({
+ field("struct", struct_({field("i32", int32()), field("f64",
float64())})),
+ field("nested", struct_({field("left", int32()),
+ field("right", struct_({field("i32", int32()),
+ field("f64",
float64())}))})),
+ });
+ ASSERT_OK_AND_ASSIGN(auto descr,
+ ProjectionDescr::FromNames({"struct.i32",
"nested.right.f64"},
+ *options_->dataset_schema))
+ SetProjection(options_.get(), std::move(descr));
+ auto batch_in = ConstantArrayGenerator::Zeroes(GetParam().items_per_batch,
schema_);
+ auto batch_out = ConstantArrayGenerator::Zeroes(
+ GetParam().items_per_batch,
+ schema({field("struct.i32", int32()), field("nested.right.f64",
float64())}));
Review Comment:
Ya...we do the field name renaming on python, and then in C++ it's left with
whatever the dotted path was. Do you think we should move the field renaming
into C++ instead?
##########
cpp/src/arrow/dataset/scanner.cc:
##########
@@ -751,7 +751,19 @@ Result<ProjectionDescr>
ProjectionDescr::FromNames(std::vector<std::string> name
const Schema&
dataset_schema) {
std::vector<compute::Expression> exprs(names.size());
for (size_t i = 0; i < exprs.size(); ++i) {
- exprs[i] = compute::field_ref(names[i]);
+ // If name isn't in schema, try finding it by dotted path.
+ if (dataset_schema.GetFieldByName(names[i]) == nullptr) {
+ auto name = names[i];
+ if (name.rfind(".", 0) != 0) {
+ name = "." + name;
+ }
+ ARROW_ASSIGN_OR_RAISE(auto field_ref, FieldRef::FromDotPath(name));
+ // safe as we know there is at least 1 dot.
+ names[i] = name.substr(name.rfind(".") + 1);
+ exprs[i] = compute::field_ref(field_ref);
Review Comment:
That's true, except `compute::field_ref` returns an `Expression` from a
`FieldRef`'; which is the vector type of `exprs`.
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