src/paimon/common/data/blob_utils.h

/*
 * 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 <cstdint>
#include <memory>
#include <set>
#include <string>
#include <unordered_map>
#include <vector>

#include "paimon/result.h"
#include "paimon/visibility.h"

namespace arrow {
class DataType;
class Field;
class KeyValueMetadata;
class ListArray;
class MapArray;
class Schema;
class StructArray;
}  // namespace arrow

namespace paimon {
class DataField;
}  // namespace paimon

namespace paimon {
/// Utils for blob type.
class PAIMON_EXPORT BlobUtils {
 public:
    BlobUtils() = delete;
    ~BlobUtils() = delete;

    struct SeparatedSchemas {
        /// Non-blob fields (includes inline blob fields when inline_fields is provided)
        std::shared_ptr<arrow::Schema> main_schema;
        /// Blob fields that go to separate .blob files
        std::shared_ptr<arrow::Schema> blob_schema;
    };

    struct SeparatedStructArrays {
        /// Non-blob fields (includes inline blob fields when inline_fields is provided).
        /// nullptr when all fields are stored in blob files.
        std::shared_ptr<arrow::StructArray> main_array;
        /// Blob fields that go to separate .blob files
        std::shared_ptr<arrow::StructArray> blob_array;
    };

    /// Separates schema with inline field awareness.
    /// BLOB fields in inline_fields stay in main_schema; other BLOB, ARRAY<BLOB> and
    /// MAP<..., BLOB> fields go to blob_schema.
    static SeparatedSchemas SeparateBlobSchema(const std::shared_ptr<arrow::Schema>& schema,
                                               const std::set<std::string>& inline_fields);

    /// Separates array with inline field awareness.
    /// BLOB fields in inline_fields stay in main_array; other BLOB, ARRAY<BLOB> and
    /// MAP<..., BLOB> fields go to blob_array.
    static Result<SeparatedStructArrays> SeparateBlobArray(
        const std::shared_ptr<arrow::StructArray>& struct_array,
        const std::set<std::string>& inline_fields);

    static bool IsBlobField(const std::shared_ptr<arrow::Field>& field);
    /// Returns whether the field is a top-level ARRAY whose elements are BLOBs.
    static bool IsArrayBlobField(const std::shared_ptr<arrow::Field>& field);
    /// Returns whether the field is a top-level MAP whose values are BLOBs.
    static bool IsMapBlobField(const std::shared_ptr<arrow::Field>& field);
    /// Returns whether the field is stored in a standalone blob file.
    static bool IsAnyBlobField(const std::shared_ptr<arrow::Field>& field);
    /// Returns whether an ARRAY<BLOB> row is the internal fallback sentinel.
    static bool IsArrayBlobPlaceholder(const arrow::ListArray& array, int64_t row);
    /// Returns whether a MAP<..., BLOB> row is the internal fallback sentinel.
    static bool IsMapBlobPlaceholder(const arrow::MapArray& array, int64_t row);
    /// Returns whether Paimon C++ supports `key_type` as the key type of MAP<..., BLOB>:
    /// BOOLEAN, TINYINT, SMALLINT, INT, BIGINT, DATE, DECIMAL, CHAR/VARCHAR and BINARY/VARBINARY.
    static bool IsSupportedMapBlobKeyType(const arrow::DataType& key_type);
    static bool IsBlobMetadata(const std::shared_ptr<const arrow::KeyValueMetadata>& metadata);
    static bool IsBlobFile(const std::string& file_name);

    static std::shared_ptr<arrow::Field> ToArrowField(
        const std::string& field_name, bool nullable = false,
        std::unordered_map<std::string, std::string> metadata = {});

    static Status ValidateBlobInlineFields(const std::shared_ptr<arrow::StructArray>& struct_array,
                                           const std::set<std::string>& field_names,
                                           const std::string& config_label);

    /// Converts inline blob DataFields from large_binary to binary type.
    /// Inline blob fields use large_binary in the table schema (because they are BLOB type),
    /// but are stored as binary in data files. This conversion aligns the field type with
    /// the actual on-disk storage format for correct reading.
    static std::vector<DataField> ConvertBlobInlineDataFields(
        const std::vector<DataField>& data_fields,
        const std::vector<std::string>& blob_inline_fields);
};

}  // namespace paimon