schema_util.h

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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.
 */
 
#pragma once
 
 
#include <memory>
#include <string>
#include <variant>
#include <vector>
 
#include "iceberg/expression/literal.h"
#include "iceberg/iceberg_export.h"
#include "iceberg/result.h"
#include "iceberg/type_fwd.h"
 
namespace iceberg {
 
struct ICEBERG_EXPORT FieldProjection {
  enum class Kind {
    kProjected,
    kMetadata,
    kConstant,
    kDefault,
    kNull,
  };
 
  using From = std::variant<std::monostate, size_t, Literal>;
 
  struct ExtraAttributes {
    virtual ~ExtraAttributes() = default;
  };
 
  Kind kind;
  From from;
  std::vector<FieldProjection> children;
  std::shared_ptr<ExtraAttributes> attributes;
};
 
struct ICEBERG_EXPORT SchemaProjection {
  std::vector<FieldProjection> fields;
};
 
enum class ProjectionMode {
  kRead,
  kWrite,
};
 
ICEBERG_EXPORT Result<SchemaProjection> Project(
    const Schema& expected_schema, const Schema& source_schema, bool prune_source,
    ProjectionMode mode = ProjectionMode::kRead);
 
ICEBERG_EXPORT std::string_view ToString(FieldProjection::Kind kind);
ICEBERG_EXPORT std::string ToString(const FieldProjection& projection);
ICEBERG_EXPORT std::string ToString(const SchemaProjection& projection);
 
}  // namespace iceberg