pitrou commented on a change in pull request #7992:
URL: https://github.com/apache/arrow/pull/7992#discussion_r477340732
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File path: cpp/src/arrow/ipc/dictionary.h
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@@ -21,96 +21,145 @@
#include <cstdint>
#include <memory>
-#include <unordered_map>
#include <utility>
#include <vector>
-#include "arrow/memory_pool.h"
+#include "arrow/result.h"
#include "arrow/status.h"
+#include "arrow/type_fwd.h"
#include "arrow/util/macros.h"
#include "arrow/util/visibility.h"
namespace arrow {
+namespace ipc {
+
+class FieldPosition {
+ public:
+ FieldPosition() : parent_(NULLPTR), index_(-1), depth_(0) {}
+
+ FieldPosition child(int index) const { return {this, index}; }
+
+ std::vector<int> path() const {
+ std::vector<int> path(depth_);
+ const FieldPosition* cur = this;
+ for (int i = depth_ - 1; i >= 0; --i) {
+ path[i] = cur->index_;
+ cur = cur->parent_;
+ }
+ return path;
+ }
+
+ protected:
+ FieldPosition(const FieldPosition* parent, int index)
+ : parent_(parent), index_(index), depth_(parent->depth_ + 1) {}
+
+ const FieldPosition* parent_;
+ int index_;
+ int depth_;
+};
-class Array;
-class DataType;
-class Field;
-class RecordBatch;
+/// \brief Map fields in a schema to dictionary ids
+///
+/// The mapping is structural, i.e. the field path (as a vector of indices)
+/// is associated to the dictionary id.
Review comment:
Will add.
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