bkietz commented on a change in pull request #9670:
URL: https://github.com/apache/arrow/pull/9670#discussion_r592357682
##########
File path: cpp/src/arrow/dataset/file_base.cc
##########
@@ -137,16 +130,69 @@ std::string FileSystemDataset::ToString() const {
return repr;
}
-Result<FragmentIterator> FileSystemDataset::GetFragmentsImpl(Expression
predicate) {
- FragmentVector fragments;
+void FileSystemDataset::SetupSubtreePruning() {
+ SubtreeImpl impl;
- for (const auto& fragment : fragments_) {
- ARROW_ASSIGN_OR_RAISE(
- auto simplified,
- SimplifyWithGuarantee(predicate, fragment->partition_expression()));
- if (simplified.IsSatisfiable()) {
- fragments.push_back(fragment);
+ auto encoded = impl.EncodeFragments(fragments_);
+
+ std::sort(encoded.begin(), encoded.end(),
+ [](const SubtreeImpl::Encoded& l, const SubtreeImpl::Encoded& r) {
+ return l.partition_expression < r.partition_expression;
+ });
+
+ for (const auto& e : encoded) {
+ if (e.fragment_index) {
+ fragments_and_subtrees_.emplace_back(*e.fragment_index);
+ } else {
+ fragments_and_subtrees_.emplace_back(impl.GetSubtreeExpression(e));
+ }
+ }
+
+ forest_ = Forest(static_cast<int>(encoded.size()), [&](int l, int r) {
+ if (encoded[l].fragment_index) {
+ // Fragment: not an ancestor.
+ return false;
+ }
+
+ const auto& ancestor = encoded[l].partition_expression;
+ const auto& descendant = encoded[r].partition_expression;
+
+ if (descendant.size() >= ancestor.size()) {
+ return std::equal(ancestor.begin(), ancestor.end(), descendant.begin());
}
+ return false;
+ });
+}
+
+Result<FragmentIterator> FileSystemDataset::GetFragmentsImpl(Expression
predicate) {
+ std::vector<int> fragment_indices;
+
+ std::vector<Expression> predicates{predicate};
+ RETURN_NOT_OK(forest_.Visit(
+ [&](Forest::Ref ref) -> Result<bool> {
+ if (auto fragment_index =
util::get_if<int>(&fragments_and_subtrees_[ref.i])) {
+ fragment_indices.push_back(*fragment_index);
+ return false;
+ }
+
+ const auto& subtree_expr =
util::get<Expression>(fragments_and_subtrees_[ref.i]);
+ ARROW_ASSIGN_OR_RAISE(auto simplified,
+ SimplifyWithGuarantee(predicates.back(),
subtree_expr));
+
+ if (!simplified.IsSatisfiable()) {
+ return false;
+ }
+
+ predicates.push_back(std::move(simplified));
+ return true;
+ },
+ [&](Forest::Ref ref) { predicates.pop_back(); }));
+
+ std::sort(fragment_indices.begin(), fragment_indices.end());
+
+ FragmentVector fragments;
+ for (int i : fragment_indices) {
+ fragments.push_back(fragments_[i]);
}
Review comment:
```suggestion
FragmentVector fragments(fragment_indices.size());
std::transform(fragment_indices.begin(), fragment_indices.end(),
fragments.begin(), [](int i) {
return fragments_[i];
});
```
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