src/paimon/common/reader/delegating_prefetch_reader.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 <utility>
#include <vector>

#include "arrow/c/bridge.h"
#include "arrow/type.h"
#include "paimon/common/reader/prefetch_file_batch_reader_impl.h"
#include "paimon/reader/file_batch_reader.h"

namespace paimon {

class DelegatingPrefetchReader : public FileBatchReader {
 public:
    explicit DelegatingPrefetchReader(std::unique_ptr<PrefetchFileBatchReaderImpl> prefetch_reader)
        : prefetch_reader_(std::move(prefetch_reader)) {}

    Result<ReadBatch> NextBatch() override {
        return Status::Invalid(
            "paimon inner reader DelegatingPrefetchReader should use NextBatchWithBitmap");
    }

    Result<ReadBatchWithBitmap> NextBatchWithBitmap() override {
        return GetReader()->NextBatchWithBitmap();
    }

    std::shared_ptr<Metrics> GetReaderMetrics() const override {
        return prefetch_reader_->GetReaderMetrics();
    }

    Result<std::unique_ptr<::ArrowSchema>> GetFileSchema() const override {
        return GetReader()->GetFileSchema();
    }

    Status SetReadSchema(::ArrowSchema* read_schema, const std::shared_ptr<Predicate>& predicate,
                         const std::optional<RoaringBitmap32>& selection_bitmap) override {
        return prefetch_reader_->SetReadSchema(read_schema, predicate, selection_bitmap);
    }

    Result<uint64_t> GetPreviousBatchFileRowId(uint64_t batch_row_id) const override {
        return GetReader()->GetPreviousBatchFileRowId(batch_row_id);
    }

    Result<uint64_t> GetNumberOfRows() const override {
        return GetReader()->GetNumberOfRows();
    }

    void Close() override {
        return prefetch_reader_->Close();
    }

    bool SupportPreciseBitmapSelection() const override {
        return GetReader()->SupportPreciseBitmapSelection();
    }

    void Warmup() override {
        // GetReader() bypasses the prefetch layer entirely when prefetching is off, and a
        // bypassed reader has no background thread to start.
        if (!prefetch_reader_->NeedPrefetch()) {
            return;
        }
        prefetch_reader_->Warmup();
    }

 private:
    inline FileBatchReader* GetReader() const {
        assert(prefetch_reader_);
        if (prefetch_reader_->NeedPrefetch()) {
            return prefetch_reader_.get();
        } else {
            return prefetch_reader_->GetFirstReader();
        }
    }

    std::unique_ptr<PrefetchFileBatchReaderImpl> prefetch_reader_;
};

}  // namespace paimon