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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
// Tools for dictionaries in IPC context
#pragma once
#include <cstdint>
#include <memory>
#include <utility>
#include <vector>
#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 {
namespace internal {
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_;
};
} // namespace internal
/// \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. A dictionary id may be associated
/// to multiple fields.
class ARROW_EXPORT DictionaryFieldMapper {
public:
DictionaryFieldMapper();
explicit DictionaryFieldMapper(const Schema& schema);
~DictionaryFieldMapper();
Status AddSchemaFields(const Schema& schema);
Status AddField(int64_t id, std::vector<int> field_path);
Result<int64_t> GetFieldId(std::vector<int> field_path) const;
int num_fields() const;
/// \brief Returns number of unique dictionaries, taking into
/// account that different fields can share the same dictionary.
int num_dicts() const;
private:
struct Impl;
std::unique_ptr<Impl> impl_;
};
using DictionaryVector = std::vector<std::pair<int64_t, std::shared_ptr<Array>>>;
/// \brief Memoization data structure for reading dictionaries from IPC streams
///
/// This structure tracks the following associations:
/// - field position (structural) -> dictionary id
/// - dictionary id -> value type
/// - dictionary id -> dictionary (value) data
///
/// Together, they allow resolving dictionary data when reading an IPC stream,
/// using metadata recorded in the schema message and data recorded in the
/// dictionary batch messages (see ResolveDictionaries).
///
/// This structure isn't useful for writing an IPC stream, where only
/// DictionaryFieldMapper is necessary.
class ARROW_EXPORT DictionaryMemo {
public:
DictionaryMemo();
~DictionaryMemo();
DictionaryFieldMapper& fields();
const DictionaryFieldMapper& fields() const;
/// \brief Return current dictionary corresponding to a particular
/// id. Returns KeyError if id not found
Result<std::shared_ptr<ArrayData>> GetDictionary(int64_t id, MemoryPool* pool) const;
/// \brief Return dictionary value type corresponding to a
/// particular dictionary id.
Result<std::shared_ptr<DataType>> GetDictionaryType(int64_t id) const;
/// \brief Return true if we have a dictionary for the input id
bool HasDictionary(int64_t id) const;
/// \brief Add a dictionary value type to the memo with a particular id.
/// Returns KeyError if a different type is already registered with the same id.
Status AddDictionaryType(int64_t id, const std::shared_ptr<DataType>& type);
/// \brief Add a dictionary to the memo with a particular id. Returns
/// KeyError if that dictionary already exists
Status AddDictionary(int64_t id, const std::shared_ptr<ArrayData>& dictionary);
/// \brief Append a dictionary delta to the memo with a particular id. Returns
/// KeyError if that dictionary does not exists
Status AddDictionaryDelta(int64_t id, const std::shared_ptr<ArrayData>& dictionary);
/// \brief Add a dictionary to the memo if it does not have one with the id,
/// otherwise, replace the dictionary with the new one.
///
/// Return true if the dictionary was added, false if replaced.
Result<bool> AddOrReplaceDictionary(int64_t id,
const std::shared_ptr<ArrayData>& dictionary);
private:
struct Impl;
std::unique_ptr<Impl> impl_;
};
// For writing: collect dictionary entries to write to the IPC stream, in order
// (i.e. inner dictionaries before dependent outer dictionaries).
ARROW_EXPORT
Result<DictionaryVector> CollectDictionaries(const RecordBatch& batch,
const DictionaryFieldMapper& mapper);
// For reading: resolve all dictionaries in columns, according to the field
// mapping and dictionary arrays stored in memo.
// Columns may be sparse, i.e. some entries may be left null
// (e.g. if an inclusion mask was used).
ARROW_EXPORT
Status ResolveDictionaries(const ArrayDataVector& columns, const DictionaryMemo& memo,
MemoryPool* pool);
namespace internal {
// Like CollectDictionaries above, but uses the memo's DictionaryFieldMapper
// and all collected dictionaries are added to the memo using AddDictionary.
//
// This is used as a shortcut in some roundtripping tests (to avoid emitting
// any actual dictionary batches).
ARROW_EXPORT
Status CollectDictionaries(const RecordBatch& batch, DictionaryMemo* memo);
} // namespace internal
} // namespace ipc
} // namespace arrow
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