include/paimon/table/source/table_read.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 <memory>
#include <vector>

#include "paimon/executor.h"
#include "paimon/read_context.h"
#include "paimon/reader/batch_reader.h"
#include "paimon/reader/count_reader.h"
#include "paimon/result.h"
#include "paimon/table/source/split.h"
#include "paimon/visibility.h"

namespace paimon {
class ReadContext;

/// Given a `Split` or a list of `Split`, generate a reader for batch reading.
///
/// A real-time split may create at most one successful reader. Calls using the same real-time
/// split must not run concurrently, and the split must not be reused by multiple queries. A failed
/// reader creation may be retried sequentially while its read-view ticket remains valid.
class PAIMON_EXPORT TableRead {
 public:
    virtual ~TableRead() = default;

    /// Create an instance of `TableRead`.
    ///
    /// @param context A unique pointer to the `ReadContext` used for read operations.
    /// @return A Result containing a unique pointer to the `TableRead` instance.
    static Result<std::unique_ptr<TableRead>> Create(std::unique_ptr<ReadContext> context);

    /// Creates a `BatchReader` instance for reading data.
    ///
    /// This method creates a BatchReader that will be responsible for reading data from the
    /// provided splits.
    ///
    /// @param splits A vector of shared pointers to `Split` instances representing the
    ///                    data to be read.
    /// @return A Result containing a unique pointer to the `BatchReader` instance.
    /// @note `BatchReader`s created by the same `TableRead` are not thread-safe for
    /// concurrent reading.
    virtual Result<std::unique_ptr<BatchReader>> CreateReader(
        const std::vector<std::shared_ptr<Split>>& splits) = 0;

    /// Creates a `BatchReader` instance for a single split.
    ///
    /// @param split A shared pointer to the `Split` instance that defines the data to be
    ///                   read.
    /// @return A Result containing a unique pointer to the `BatchReader` instance.
    virtual Result<std::unique_ptr<BatchReader>> CreateReader(
        const std::shared_ptr<Split>& split) = 0;

    /// Creates a `CountReader` for count queries on the specified splits.
    ///
    /// Implementations may override this to provide a more efficient count path.
    virtual Result<std::unique_ptr<CountReader>> CreateCountReader(
        const std::vector<std::shared_ptr<Split>>& splits);
};
}  // namespace paimon