// 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 <gen_cpp/Descriptors_types.h>

#include <gen_cpp/segment_v2.pb.h>

#include <glog/logging.h>

#include <sys/types.h>

#include <cstddef> // for size_t

#include <cstdint> // for uint32_t

#include <map>

#include <memory> // for unique_ptr

#include <string>

#include <utility>

#include <vector>

#include "common/config.h"

#include "common/logging.h"

#include "common/status.h"            // for Status

#include "core/column/column_array.h" // ColumnArray

#include "core/data_type/data_type.h"

#include "io/cache/cached_remote_file_reader.h"

#include "io/fs/file_reader_writer_fwd.h"

#include "io/io_common.h"

#include "storage/index/index_reader.h"

#include "storage/index/ordinal_page_index.h" // for OrdinalPageIndexIterator

#include "storage/index/zone_map/zone_map_index.h"

#include "storage/olap_common.h"

#include "storage/predicate/column_predicate.h"

#include "storage/segment/common.h"

#include "storage/segment/page_handle.h" // for PageHandle

#include "storage/segment/page_pointer.h"

#include "storage/segment/parsed_page.h" // for ParsedPage

#include "storage/segment/segment_prefetcher.h"

#include "storage/segment/stream_reader.h"

#include "storage/tablet/tablet_schema.h"

#include "storage/types.h"

#include "storage/utils.h"

#include "util/once.h"

namespace doris {

class BlockCompressionCodec;

class AndBlockColumnPredicate;

class ColumnPredicate;

class TabletIndex;

class StorageReadOptions;

namespace io {

class FileReader;

} // namespace io

struct Slice;

struct StringRef;

using TColumnAccessPaths = std::vector<TColumnAccessPath>;

namespace segment_v2 {

class EncodingInfo;

class ColumnIterator;

class BloomFilterIndexReader;

class InvertedIndexIterator;

class InvertedIndexReader;

class IndexFileReader;

class PageDecoder;

class RowRanges;

class ZoneMapIndexReader;

class IndexIterator;

class ColumnMetaAccessor;

struct ColumnReaderOptions {

    // whether verify checksum when read page

    bool verify_checksum = true;

    // for in memory olap table, use DURABLE CachePriority in page cache

    bool kept_in_memory = false;

    int be_exec_version = -1;

    TabletSchemaSPtr tablet_schema = nullptr;

};

struct ColumnIteratorOptions {

    bool use_page_cache = false;

    bool is_predicate_column = false;

    // for page cache allocation

    // page types are divided into DATA_PAGE & INDEX_PAGE

    // INDEX_PAGE including index_page, dict_page and short_key_page

    PageTypePB type = PageTypePB::UNKNOWN_PAGE_TYPE;

    io::FileReader* file_reader = nullptr; // Ref

    // reader statistics

    OlapReaderStatistics* stats = nullptr; // Ref

    io::IOContext io_ctx;

    bool only_read_offsets = false;

    void sanity_check() const {

        CHECK_NOTNULL(file_reader);

        CHECK_NOTNULL(stats);

    }

};

class ColumnIterator;

class OffsetFileColumnIterator;

class FileColumnIterator;

using ColumnIteratorUPtr = std::unique_ptr<ColumnIterator>;

using OffsetFileColumnIteratorUPtr = std::unique_ptr<OffsetFileColumnIterator>;

using FileColumnIteratorUPtr = std::unique_ptr<FileColumnIterator>;

using ColumnIteratorSPtr = std::shared_ptr<ColumnIterator>;

// There will be concurrent users to read the same column. So

// we should do our best to reduce resource usage through share

// same information, such as OrdinalPageIndex and Page data.

// This will cache data shared by all reader

class ColumnReader : public MetadataAdder<ColumnReader>,

                     public std::enable_shared_from_this<ColumnReader> {

public:

    ColumnReader();

    // Create an initialized ColumnReader in *reader.

    // This should be a lightweight operation without I/O.

    static Status create(const ColumnReaderOptions& opts, const ColumnMetaPB& meta,

                         uint64_t num_rows, const io::FileReaderSPtr& file_reader,

                         std::shared_ptr<ColumnReader>* reader);

    static Status create_array(const ColumnReaderOptions& opts, const ColumnMetaPB& meta,

                               const io::FileReaderSPtr& file_reader,

                               std::shared_ptr<ColumnReader>* reader);

    static Status create_map(const ColumnReaderOptions& opts, const ColumnMetaPB& meta,

                             const io::FileReaderSPtr& file_reader,

                             std::shared_ptr<ColumnReader>* reader);

    static Status create_struct(const ColumnReaderOptions& opts, const ColumnMetaPB& meta,

                                uint64_t num_rows, const io::FileReaderSPtr& file_reader,

                                std::shared_ptr<ColumnReader>* reader);

    static Status create_agg_state(const ColumnReaderOptions& opts, const ColumnMetaPB& meta,

                                   uint64_t num_rows, const io::FileReaderSPtr& file_reader,

                                   std::shared_ptr<ColumnReader>* reader);

    enum DictEncodingType { UNKNOWN_DICT_ENCODING, PARTIAL_DICT_ENCODING, ALL_DICT_ENCODING };

    static bool is_compaction_reader_type(ReaderType type);

    ~ColumnReader() override;

    // create a new column iterator. Client should delete returned iterator

    virtual Status new_iterator(ColumnIteratorUPtr* iterator, const TabletColumn* col,

                                const StorageReadOptions*);

    Status new_iterator(ColumnIteratorUPtr* iterator, const TabletColumn* tablet_column);

    Status new_array_iterator(ColumnIteratorUPtr* iterator, const TabletColumn* tablet_column);

    Status new_struct_iterator(ColumnIteratorUPtr* iterator, const TabletColumn* tablet_column);

    Status new_map_iterator(ColumnIteratorUPtr* iterator, const TabletColumn* tablet_column);

    Status new_agg_state_iterator(ColumnIteratorUPtr* iterator);

    Status new_index_iterator(const std::shared_ptr<IndexFileReader>& index_file_reader,

                              const TabletIndex* index_meta, const std::string& rowset_id,

                              uint32_t segment_id, size_t rows_of_segment,

                              std::unique_ptr<IndexIterator>* iterator);

    Status seek_at_or_before(ordinal_t ordinal, OrdinalPageIndexIterator* iter,

                             const ColumnIteratorOptions& iter_opts);

    Status get_ordinal_index_reader(OrdinalIndexReader*& reader,

                                    OlapReaderStatistics* index_load_stats);

    // read a page from file into a page handle

    Status read_page(const ColumnIteratorOptions& iter_opts, const PagePointer& pp,

                     PageHandle* handle, Slice* page_body, PageFooterPB* footer,

                     BlockCompressionCodec* codec, bool is_dict_page = false) const;

    bool is_nullable() const { return _meta_is_nullable; }

    const EncodingInfo* encoding_info() const { return _encoding_info; }

    bool has_zone_map() const { return _zone_map_index != nullptr; }

    bool has_bloom_filter_index(bool ngram) const;

    // Check if this column could match `cond' using segment zone map.

    // Since segment zone map is stored in metadata, this function is fast without I/O.

    // set matched to true if segment zone map is absent or `cond' could be satisfied, false otherwise.

    Status match_condition(const AndBlockColumnPredicate* col_predicates, bool* matched) const;

    Status next_batch_of_zone_map(size_t* n, MutableColumnPtr& dst) const;

    // get row ranges with zone map

    // - cond_column is user's query predicate

    // - delete_condition is a delete predicate of one version

    Status get_row_ranges_by_zone_map(

            const AndBlockColumnPredicate* col_predicates,

            const std::vector<std::shared_ptr<const ColumnPredicate>>* delete_predicates,

            RowRanges* row_ranges, const ColumnIteratorOptions& iter_opts);

    // get row ranges with bloom filter index

    Status get_row_ranges_by_bloom_filter(const AndBlockColumnPredicate* col_predicates,

                                          RowRanges* row_ranges,

                                          const ColumnIteratorOptions& iter_opts);

    PagePointer get_dict_page_pointer() const { return _meta_dict_page; }

    bool is_empty() const { return _num_rows == 0; }

    Status prune_predicates_by_zone_map(std::vector<std::shared_ptr<ColumnPredicate>>& predicates,

                                        const int column_id, bool* pruned) const;

    CompressionTypePB get_compression() const { return _meta_compression; }

    uint64_t num_rows() const { return _num_rows; }

    void set_dict_encoding_type(DictEncodingType type) {

        static_cast<void>(_set_dict_encoding_type_once.call([&] {

            _dict_encoding_type = type;

            return Status::OK();

        }));

    }

    DictEncodingType get_dict_encoding_type() { return _dict_encoding_type; }

    void disable_index_meta_cache() { _use_index_page_cache = false; }

    DataTypePtr get_vec_data_type() { return _data_type; }

    virtual FieldType get_meta_type() { return _meta_type; }

    int64_t get_metadata_size() const override;

#ifdef BE_TEST

    void check_data_by_zone_map_for_test(const MutableColumnPtr& dst) const;

#endif

private:

    friend class VariantColumnReader;

    friend class FileColumnIterator;

    friend class SegmentPrefetcher;

    ColumnReader(const ColumnReaderOptions& opts, const ColumnMetaPB& meta, uint64_t num_rows,

                 io::FileReaderSPtr file_reader);

    Status init(const ColumnMetaPB* meta);

    [[nodiscard]] Status _load_zone_map_index(bool use_page_cache, bool kept_in_memory,

                                              const ColumnIteratorOptions& iter_opts);

    [[nodiscard]] Status _load_ordinal_index(bool use_page_cache, bool kept_in_memory,

                                             const ColumnIteratorOptions& iter_opts);

    [[nodiscard]] Status _load_index(const std::shared_ptr<IndexFileReader>& index_file_reader,

                                     const TabletIndex* index_meta, const std::string& rowset_id,

                                     uint32_t segment_id, size_t rows_of_segment);

    [[nodiscard]] Status _load_bloom_filter_index(bool use_page_cache, bool kept_in_memory,

                                                  const ColumnIteratorOptions& iter_opts);

    bool _zone_map_match_condition(const segment_v2::ZoneMap& zone_map,

                                   const AndBlockColumnPredicate* col_predicates) const;

    Status _get_filtered_pages(

            const AndBlockColumnPredicate* col_predicates,

            const std::vector<std::shared_ptr<const ColumnPredicate>>* delete_predicates,

            std::vector<uint32_t>* page_indexes, const ColumnIteratorOptions& iter_opts);

    Status _calculate_row_ranges(const std::vector<uint32_t>& page_indexes, RowRanges* row_ranges,

                                 const ColumnIteratorOptions& iter_opts);

    int64_t _meta_length;

    FieldType _meta_type;

    FieldType _meta_children_column_type;

    bool _meta_is_nullable;

    bool _use_index_page_cache;

    int _be_exec_version = -1;

    PagePointer _meta_dict_page;

    CompressionTypePB _meta_compression;

    ColumnReaderOptions _opts;

    uint64_t _num_rows;

    io::FileReaderSPtr _file_reader;

    DictEncodingType _dict_encoding_type;

    DataTypePtr _data_type;

    FieldType _type =

            FieldType::OLAP_FIELD_TYPE_NONE; // initialized in init(), may changed by subclasses.

    const EncodingInfo* _encoding_info =

            nullptr; // initialized in init(), used for create PageDecoder

    // meta for various column indexes (null if the index is absent)

    std::unique_ptr<ZoneMapPB> _segment_zone_map;

    mutable std::shared_mutex _load_index_lock;

    std::unique_ptr<ZoneMapIndexReader> _zone_map_index;

    std::unique_ptr<OrdinalIndexReader> _ordinal_index;

    std::shared_ptr<BloomFilterIndexReader> _bloom_filter_index;

    std::unordered_map<int64_t, IndexReaderPtr> _index_readers;

    std::vector<std::shared_ptr<ColumnReader>> _sub_readers;

    DorisCallOnce<Status> _set_dict_encoding_type_once;

};

// Base iterator to read one column data

class ColumnIterator {

public:

    ColumnIterator() = default;

    virtual ~ColumnIterator() = default;

    virtual Status init(const ColumnIteratorOptions& opts) {

        _opts = opts;

        return Status::OK();

    }

    // Seek to the given ordinal entry in the column.

    // Entry 0 is the first entry written to the column.

    // If provided seek point is past the end of the file,

    // then returns false.

    virtual Status seek_to_ordinal(ordinal_t ord) = 0;

    Status next_batch(size_t* n, MutableColumnPtr& dst) {

        bool has_null;

        return next_batch(n, dst, &has_null);

    }

    virtual Status next_batch(size_t* n, MutableColumnPtr& dst, bool* has_null) {

        return Status::NotSupported("next_batch not implement");

    }

    virtual Status next_batch_of_zone_map(size_t* n, MutableColumnPtr& dst) {

        return Status::NotSupported("next_batch_of_zone_map not implement");

    }

    virtual Status read_by_rowids(const rowid_t* rowids, const size_t count,

                                  MutableColumnPtr& dst) {

        return Status::NotSupported("read_by_rowids not implement");

    }

    virtual ordinal_t get_current_ordinal() const = 0;

    virtual Status get_row_ranges_by_zone_map(

            const AndBlockColumnPredicate* col_predicates,

            const std::vector<std::shared_ptr<const ColumnPredicate>>* delete_predicates,

            RowRanges* row_ranges) {

        return Status::OK();

    }

    virtual Status get_row_ranges_by_bloom_filter(const AndBlockColumnPredicate* col_predicates,

                                                  RowRanges* row_ranges) {

        return Status::OK();

    }

    virtual Status get_row_ranges_by_dict(const AndBlockColumnPredicate* col_predicates,

                                          RowRanges* row_ranges) {

        return Status::OK();

    }

    virtual bool is_all_dict_encoding() const { return false; }

    virtual Status set_access_paths(const TColumnAccessPaths& all_access_paths,

                                    const TColumnAccessPaths& predicate_access_paths) {

        if (!predicate_access_paths.empty()) {

            _reading_flag = ReadingFlag::READING_FOR_PREDICATE;

        }

        return Status::OK();

    }

    void set_column_name(const std::string& column_name) { _column_name = column_name; }

    const std::string& column_name() const { return _column_name; }

    // Since there may be multiple paths with conflicts or overlaps,

    // we need to define several reading flags:

    //

    // NORMAL_READING — Default value, indicating that the column should be read.

    // SKIP_READING — The column should not be read.

    // NEED_TO_READ — The column must be read.

    // READING_FOR_PREDICATE — The column is required for predicate evaluation.

    //

    // For example, suppose there are two paths:

    // - Path 1 specifies that column A needs to be read, so it is marked as NEED_TO_READ.

    // - Path 2 specifies that the column should not be read, but since it is already marked as NEED_TO_READ,

    //   it should not be changed to SKIP_READING.

    enum class ReadingFlag : int {

        NORMAL_READING,

        SKIP_READING,

        NEED_TO_READ,

        READING_FOR_PREDICATE

    };

    void set_reading_flag(ReadingFlag flag) {

        if (static_cast<int>(flag) > static_cast<int>(_reading_flag)) {

            _reading_flag = flag;

        }

    }

    ReadingFlag reading_flag() const { return _reading_flag; }

    virtual void set_need_to_read() { set_reading_flag(ReadingFlag::NEED_TO_READ); }

    virtual void remove_pruned_sub_iterators() {};

    virtual Status init_prefetcher(const SegmentPrefetchParams& params) { return Status::OK(); }

    virtual void collect_prefetchers(

            std::map<PrefetcherInitMethod, std::vector<SegmentPrefetcher*>>& prefetchers,

            PrefetcherInitMethod init_method) {}

    static constexpr const char* ACCESS_OFFSET = "OFFSET";

    static constexpr const char* ACCESS_ALL = "*";

    static constexpr const char* ACCESS_MAP_KEYS = "KEYS";

    static constexpr const char* ACCESS_MAP_VALUES = "VALUES";

    static constexpr const char* ACCESS_NULL = "NULL";

    // Meta-only read modes:

    // - OFFSET_ONLY: only read offset information (e.g., for array_size/map_size/string_length)

    // - NULL_MAP_ONLY: only read null map (e.g., for IS NULL / IS NOT NULL predicates)

    // When these modes are enabled, actual content data is skipped.

    enum class ReadMode : int { DEFAULT, OFFSET_ONLY, NULL_MAP_ONLY };

    bool read_offset_only() const { return _read_mode == ReadMode::OFFSET_ONLY; }

    bool read_null_map_only() const { return _read_mode == ReadMode::NULL_MAP_ONLY; }

    enum class ReadingMode : int {

        NORMAL, // default mode

        PREDICATE,

        LAZY

    };

    virtual void set_reading_mode(ReadingMode mode) {

        _reading_mode = mode;

        if (mode == ReadingMode::PREDICATE) {

            _has_place_holder_column = false;

        }

    }

    virtual bool need_to_read() const {

        switch (_reading_mode) {

        case ReadingMode::NORMAL:

            return _reading_flag != ReadingFlag::SKIP_READING;

        case ReadingMode::PREDICATE:

            return _reading_flag == ReadingFlag::READING_FOR_PREDICATE;

        case ReadingMode::LAZY:

            return _reading_flag == ReadingFlag::NEED_TO_READ;

        default:

            return false;

        }

    }

    // Whether need to read meta columns, such as null map column, offset column.

    bool need_to_read_meta_columns() const {

        if (_reading_flag == ReadingFlag::SKIP_READING) {

            return false;

        }

        switch (_reading_mode) {

        case ReadingMode::NORMAL:

        case ReadingMode::PREDICATE:

            return true;

        case ReadingMode::LAZY:

            return _reading_flag != ReadingFlag::READING_FOR_PREDICATE;

        }

        return false;

    }

    virtual void finalize_lazy_mode(MutableColumnPtr& dst) {

        _recovery_from_place_holder_column(dst);

    }

    virtual void set_reading_flag_recursively(ReadingFlag flag) { set_reading_flag(flag); }

    // Whether this iterator or any nested iterator has data that must be materialized

    // in lazy mode. Predicate-only and meta-only branches are read before filtering and

    // must not be re-read in the lazy phase.

    virtual bool has_lazy_read_target() const { return _reading_flag == ReadingFlag::NEED_TO_READ; }

    bool is_pruned() const { return _pruned; }

protected:

    void _convert_to_place_holder_column(MutableColumnPtr& dst, size_t count);

    void _recovery_from_place_holder_column(MutableColumnPtr& dst);

    // Checks sub access paths for OFFSET or NULL meta-only modes and

    // updates _read_mode accordingly. Use the accessor helpers

    // read_offset_only() / read_null_map_only() to query the current mode.

    void _check_and_set_meta_read_mode(const TColumnAccessPaths& sub_all_access_paths);

    Result<TColumnAccessPaths> _get_sub_access_paths(const TColumnAccessPaths& access_paths);

    Result<TColumnAccessPaths> _process_sub_access_paths(const TColumnAccessPaths& access_paths,

                                                         const bool is_predicate);

    ColumnIteratorOptions _opts;

    ReadingFlag _reading_flag {ReadingFlag::NORMAL_READING};

    ReadMode _read_mode = ReadMode::DEFAULT;

    ReadingMode _reading_mode {ReadingMode::NORMAL};

    std::string _column_name;

    bool _pruned {false};

    bool _has_place_holder_column {false};

};

// This iterator is used to read column data from file

// for scalar type

class FileColumnIterator : public ColumnIterator {

public:

    explicit FileColumnIterator(std::shared_ptr<ColumnReader> reader);

    ~FileColumnIterator() override;

    Status init(const ColumnIteratorOptions& opts) override;

    Status seek_to_ordinal(ordinal_t ord) override;

    Status seek_to_page_start();

    Status next_batch(size_t* n, MutableColumnPtr& dst, bool* has_null) override;

    Status next_batch_of_zone_map(size_t* n, MutableColumnPtr& dst) override;

    Status read_by_rowids(const rowid_t* rowids, const size_t count,

                          MutableColumnPtr& dst) override;

    ordinal_t get_current_ordinal() const override { return _current_ordinal; }

    // get row ranges by zone map

    // - cond_column is user's query predicate

    // - delete_condition is delete predicate of one version

    Status get_row_ranges_by_zone_map(

            const AndBlockColumnPredicate* col_predicates,

            const std::vector<std::shared_ptr<const ColumnPredicate>>* delete_predicates,

            RowRanges* row_ranges) override;

    Status get_row_ranges_by_bloom_filter(const AndBlockColumnPredicate* col_predicates,

                                          RowRanges* row_ranges) override;

    Status get_row_ranges_by_dict(const AndBlockColumnPredicate* col_predicates,

                                  RowRanges* row_ranges) override;

    ParsedPage* get_current_page() { return &_page; }

    bool is_nullable() { return _reader->is_nullable(); }

    bool is_all_dict_encoding() const override { return _is_all_dict_encoding; }

    Status init_prefetcher(const SegmentPrefetchParams& params) override;

    void collect_prefetchers(

            std::map<PrefetcherInitMethod, std::vector<SegmentPrefetcher*>>& prefetchers,

            PrefetcherInitMethod init_method) override;

protected:

    // Exposed to derived iterators (e.g. StringFileColumnIterator) so they can

    // query column metadata such as the storage field type.

    const std::shared_ptr<ColumnReader>& get_reader() const { return _reader; }

private:

    Status _seek_to_pos_in_page(ParsedPage* page, ordinal_t offset_in_page) const;

    Status _load_next_page(bool* eos);

    Status _read_data_page(const OrdinalPageIndexIterator& iter);

    Status _read_dict_data();

    void _trigger_prefetch_if_eligible(ordinal_t ord);

    std::shared_ptr<ColumnReader> _reader = nullptr;

    BlockCompressionCodec* _compress_codec = nullptr;

    // 1. The _page represents current page.

    // 2. We define an operation is one seek and following read,

    //    If new seek is issued, the _page will be reset.

    ParsedPage _page;

    // keep dict page decoder

    std::unique_ptr<PageDecoder> _dict_decoder;

    // keep dict page handle to avoid released

    PageHandle _dict_page_handle;

    // page iterator used to get next page when current page is finished.

    // This value will be reset when a new seek is issued

    OrdinalPageIndexIterator _page_iter;

    // current value ordinal

    ordinal_t _current_ordinal = 0;

    bool _is_all_dict_encoding = false;

    std::unique_ptr<StringRef[]> _dict_word_info;

    bool _enable_prefetch {false};

    std::unique_ptr<SegmentPrefetcher> _prefetcher;

    std::shared_ptr<io::CachedRemoteFileReader> _cached_remote_file_reader {nullptr};

};

class EmptyFileColumnIterator final : public ColumnIterator {

public:

    Status seek_to_ordinal(ordinal_t ord) override { return Status::OK(); }

    ordinal_t get_current_ordinal() const override { return 0; }

};

// StringFileColumnIterator extends FileColumnIterator with meta-only reading

// support for string/binary column types. When the OFFSET path is detected in

// set_access_paths, it sets only_read_offsets on the ColumnIteratorOptions so

// that the BinaryPlainPageDecoder skips chars memcpy and only fills offsets.

class StringFileColumnIterator final : public FileColumnIterator {

public:

    explicit StringFileColumnIterator(std::shared_ptr<ColumnReader> reader);

    ~StringFileColumnIterator() override = default;

    Status init(const ColumnIteratorOptions& opts) override;

    Status set_access_paths(const TColumnAccessPaths& all_access_paths,

                            const TColumnAccessPaths& predicate_access_paths) override;

};

// This iterator make offset operation write once for

class OffsetFileColumnIterator final : public ColumnIterator {

public:

    explicit OffsetFileColumnIterator(FileColumnIteratorUPtr offset_reader) {

        _offset_iterator = std::move(offset_reader);

    }

    ~OffsetFileColumnIterator() override = default;

    Status init(const ColumnIteratorOptions& opts) override;

    Status next_batch(size_t* n, MutableColumnPtr& dst, bool* has_null) override;

    Status next_batch(size_t* n, MutableColumnPtr& dst) {

        bool has_null;

        return next_batch(n, dst, &has_null);

    }

    ordinal_t get_current_ordinal() const override {

        return _offset_iterator->get_current_ordinal();

    }

    Status seek_to_ordinal(ordinal_t ord) override {

        RETURN_IF_ERROR(_offset_iterator->seek_to_ordinal(ord));

        return Status::OK();

    }

    Status _peek_one_offset(ordinal_t* offset);

    Status _calculate_offsets(ssize_t start, ColumnArray::ColumnOffsets& column_offsets);

    Status read_by_rowids(const rowid_t* rowids, const size_t count,

                          MutableColumnPtr& dst) override {

        return _offset_iterator->read_by_rowids(rowids, count, dst);

    }

    Status init_prefetcher(const SegmentPrefetchParams& params) override;

    void collect_prefetchers(

            std::map<PrefetcherInitMethod, std::vector<SegmentPrefetcher*>>& prefetchers,

            PrefetcherInitMethod init_method) override;

private:

    std::unique_ptr<FileColumnIterator> _offset_iterator;

    // reuse a tiny column for peek to avoid frequent allocations

    MutableColumnPtr _peek_tmp_col;

};

// This iterator is used to read map value column

class MapFileColumnIterator final : public ColumnIterator {

public:

    explicit MapFileColumnIterator(std::shared_ptr<ColumnReader> reader,

                                   ColumnIteratorUPtr null_iterator,

                                   OffsetFileColumnIteratorUPtr offsets_iterator,

                                   ColumnIteratorUPtr key_iterator,

                                   ColumnIteratorUPtr val_iterator);

    ~MapFileColumnIterator() override = default;

    Status init(const ColumnIteratorOptions& opts) override;

    Status next_batch(size_t* n, MutableColumnPtr& dst, bool* has_null) override;

    Status read_by_rowids(const rowid_t* rowids, const size_t count,

                          MutableColumnPtr& dst) override;

    Status seek_to_ordinal(ordinal_t ord) override;

    ordinal_t get_current_ordinal() const override {

        if (read_null_map_only() && _null_iterator) {

            return _null_iterator->get_current_ordinal();

        }

        return _offsets_iterator->get_current_ordinal();

    }

    Status init_prefetcher(const SegmentPrefetchParams& params) override;

    void collect_prefetchers(

            std::map<PrefetcherInitMethod, std::vector<SegmentPrefetcher*>>& prefetchers,

            PrefetcherInitMethod init_method) override;

    Status set_access_paths(const TColumnAccessPaths& all_access_paths,

                            const TColumnAccessPaths& predicate_access_paths) override;

    void set_need_to_read() override;

    void remove_pruned_sub_iterators() override;

    void set_reading_mode(ReadingMode mode) override;

    bool need_to_read() const override {

        switch (_reading_mode) {

        case ReadingMode::NORMAL:

            return _reading_flag != ReadingFlag::SKIP_READING;

        case ReadingMode::PREDICATE:

            return _reading_flag == ReadingFlag::READING_FOR_PREDICATE;

        case ReadingMode::LAZY:

            // In lazy mode, read this map only when at least one key/value branch still

            // has non-predicate data to materialize.

            return has_lazy_read_target();

        default:

            return false;

        }

    }

    void finalize_lazy_mode(MutableColumnPtr& dst) override;

    void set_reading_flag_recursively(ReadingFlag flag) override;

    bool has_lazy_read_target() const override;

private:

    std::shared_ptr<ColumnReader> _map_reader = nullptr;

    ColumnIteratorUPtr _null_iterator;

    OffsetFileColumnIteratorUPtr _offsets_iterator; //OffsetFileIterator

    ColumnIteratorUPtr _key_iterator;

    ColumnIteratorUPtr _val_iterator;

};

class StructFileColumnIterator final : public ColumnIterator {

public:

    explicit StructFileColumnIterator(std::shared_ptr<ColumnReader> reader,

                                      ColumnIteratorUPtr null_iterator,

                                      std::vector<ColumnIteratorUPtr>&& sub_column_iterators);

    ~StructFileColumnIterator() override = default;

    Status init(const ColumnIteratorOptions& opts) override;

    Status next_batch(size_t* n, MutableColumnPtr& dst, bool* has_null) override;

    Status next_batch(size_t* n, MutableColumnPtr& dst) {

        bool has_null;

        return next_batch(n, dst, &has_null);

    }

    Status read_by_rowids(const rowid_t* rowids, const size_t count,

                          MutableColumnPtr& dst) override;

    Status seek_to_ordinal(ordinal_t ord) override;

    ordinal_t get_current_ordinal() const override {

        if (read_null_map_only() && _null_iterator) {

            return _null_iterator->get_current_ordinal();

        }

        return _sub_column_iterators[0]->get_current_ordinal();

    }

    Status set_access_paths(const TColumnAccessPaths& all_access_paths,

                            const TColumnAccessPaths& predicate_access_paths) override;

    void set_need_to_read() override;

    void remove_pruned_sub_iterators() override;

    Status init_prefetcher(const SegmentPrefetchParams& params) override;

    void collect_prefetchers(

            std::map<PrefetcherInitMethod, std::vector<SegmentPrefetcher*>>& prefetchers,

            PrefetcherInitMethod init_method) override;

    void set_reading_mode(ReadingMode mode) override;

    bool need_to_read() const override {

        switch (_reading_mode) {

        case ReadingMode::NORMAL:

            return _reading_flag != ReadingFlag::SKIP_READING;

        case ReadingMode::PREDICATE:

            return _reading_flag == ReadingFlag::READING_FOR_PREDICATE;

        case ReadingMode::LAZY:

            // In lazy mode, read this struct only when at least one nested branch still

            // has non-predicate data to materialize.

            return has_lazy_read_target();

        default:

            return false;

        }

    }

    void finalize_lazy_mode(MutableColumnPtr& dst) override;

    void set_reading_flag_recursively(ReadingFlag flag) override;

    bool has_lazy_read_target() const override;

private:

    std::shared_ptr<ColumnReader> _struct_reader = nullptr;

    ColumnIteratorUPtr _null_iterator;

    std::vector<ColumnIteratorUPtr> _sub_column_iterators;

};

class ArrayFileColumnIterator final : public ColumnIterator {

public:

    explicit ArrayFileColumnIterator(std::shared_ptr<ColumnReader> reader,

                                     OffsetFileColumnIteratorUPtr offset_reader,

                                     ColumnIteratorUPtr item_iterator,

                                     ColumnIteratorUPtr null_iterator);

    ~ArrayFileColumnIterator() override = default;

    Status init(const ColumnIteratorOptions& opts) override;

    Status next_batch(size_t* n, MutableColumnPtr& dst, bool* has_null) override;

    Status next_batch(size_t* n, MutableColumnPtr& dst) {

        bool has_null;

        return next_batch(n, dst, &has_null);

    }

    Status read_by_rowids(const rowid_t* rowids, const size_t count,

                          MutableColumnPtr& dst) override;

    Status seek_to_ordinal(ordinal_t ord) override;

    ordinal_t get_current_ordinal() const override {

        if (read_null_map_only() && _null_iterator) {

            return _null_iterator->get_current_ordinal();

        }

        return _offset_iterator->get_current_ordinal();

    }

    Status set_access_paths(const TColumnAccessPaths& all_access_paths,

                            const TColumnAccessPaths& predicate_access_paths) override;

    void set_need_to_read() override;

    void remove_pruned_sub_iterators() override;

    Status init_prefetcher(const SegmentPrefetchParams& params) override;

    void collect_prefetchers(

            std::map<PrefetcherInitMethod, std::vector<SegmentPrefetcher*>>& prefetchers,

            PrefetcherInitMethod init_method) override;

    void set_reading_mode(ReadingMode mode) override;

    bool need_to_read() const override {

        switch (_reading_mode) {

        case ReadingMode::NORMAL:

            return _reading_flag != ReadingFlag::SKIP_READING;

        case ReadingMode::PREDICATE:

            return _reading_flag == ReadingFlag::READING_FOR_PREDICATE;

        case ReadingMode::LAZY:

            // In lazy mode, read this array only when its item branch still has

            // non-predicate data to materialize.

            return has_lazy_read_target();

        default:

            return false;

        }

    }

    void finalize_lazy_mode(MutableColumnPtr& dst) override;

    void set_reading_flag_recursively(ReadingFlag flag) override;

    bool has_lazy_read_target() const override;

private:

    std::shared_ptr<ColumnReader> _array_reader = nullptr;

    std::unique_ptr<OffsetFileColumnIterator> _offset_iterator;

    std::unique_ptr<ColumnIterator> _null_iterator;

    std::unique_ptr<ColumnIterator> _item_iterator;

    Status _seek_by_offsets(ordinal_t ord);

};

class RowIdColumnIterator : public ColumnIterator {

public:

    RowIdColumnIterator() = delete;

    RowIdColumnIterator(int64_t tid, RowsetId rid, int32_t segid)

            : _tablet_id(tid), _rowset_id(rid), _segment_id(segid) {}

    Status seek_to_ordinal(ordinal_t ord_idx) override {

        _current_rowid = cast_set<uint32_t>(ord_idx);

        return Status::OK();

    }

    Status next_batch(size_t* n, MutableColumnPtr& dst) {

        bool has_null;

        return next_batch(n, dst, &has_null);

    }

    Status next_batch(size_t* n, MutableColumnPtr& dst, bool* has_null) override {

        for (size_t i = 0; i < *n; ++i) {

            const auto row_id = cast_set<uint32_t>(_current_rowid + i);

            GlobalRowLoacation location(_tablet_id, _rowset_id, _segment_id, row_id);

            dst->insert_data(reinterpret_cast<const char*>(&location), sizeof(GlobalRowLoacation));

        }

        _current_rowid += *n;

        return Status::OK();

    }

    Status read_by_rowids(const rowid_t* rowids, const size_t count,

                          MutableColumnPtr& dst) override {

        for (size_t i = 0; i < count; ++i) {

            rowid_t row_id = rowids[i];

            GlobalRowLoacation location(_tablet_id, _rowset_id, _segment_id, row_id);

            dst->insert_data(reinterpret_cast<const char*>(&location), sizeof(GlobalRowLoacation));

        }

        return Status::OK();

    }

    ordinal_t get_current_ordinal() const override { return _current_rowid; }

private:

    rowid_t _current_rowid = 0;

    int64_t _tablet_id = 0;

    RowsetId _rowset_id;

    int32_t _segment_id = 0;

};

// Add new RowIdColumnIteratorV2

class RowIdColumnIteratorV2 : public ColumnIterator {

public:

    RowIdColumnIteratorV2(uint8_t version, int64_t backend_id, uint32_t file_id)

            : _version(version), _backend_id(backend_id), _file_id(file_id) {}

    Status seek_to_ordinal(ordinal_t ord_idx) override {

        _current_rowid = cast_set<uint32_t>(ord_idx);

        return Status::OK();

    }

    Status next_batch(size_t* n, MutableColumnPtr& dst) {

        bool has_null;

        return next_batch(n, dst, &has_null);

    }

    Status next_batch(size_t* n, MutableColumnPtr& dst, bool* has_null) override;

    Status read_by_rowids(const rowid_t* rowids, const size_t count,

                          MutableColumnPtr& dst) override;

    ordinal_t get_current_ordinal() const override { return _current_rowid; }

private:

    uint32_t _current_rowid = 0;

    uint8_t _version;

    int64_t _backend_id;

    uint32_t _file_id;

};

// This iterator is used to read default value column

class DefaultValueColumnIterator : public ColumnIterator {

public:

    DefaultValueColumnIterator(bool has_default_value, std::string default_value, bool is_nullable,

                               FieldType type, int precision, int scale, int len)

            : _has_default_value(has_default_value),

              _default_value(std::move(default_value)),

              _is_nullable(is_nullable),

              _type(type),

              _precision(precision),

              _scale(scale),

              _len(len) {}

    Status init(const ColumnIteratorOptions& opts) override;

    Status seek_to_ordinal(ordinal_t ord_idx) override {

        _current_rowid = ord_idx;

        return Status::OK();

    }

    Status next_batch(size_t* n, MutableColumnPtr& dst) {

        bool has_null;

        return next_batch(n, dst, &has_null);

    }

    Status next_batch(size_t* n, MutableColumnPtr& dst, bool* has_null) override;

    Status next_batch_of_zone_map(size_t* n, MutableColumnPtr& dst) override {

        return next_batch(n, dst);

    }

    Status read_by_rowids(const rowid_t* rowids, const size_t count,

                          MutableColumnPtr& dst) override;

    ordinal_t get_current_ordinal() const override { return _current_rowid; }

private:

    void _insert_many_default(MutableColumnPtr& dst, size_t n);

    bool _has_default_value;

    std::string _default_value;

    bool _is_nullable;

    FieldType _type;

    int _precision;

    int _scale;

    const int _len;

    Field _default_value_field;

    // current rowid

    ordinal_t _current_rowid = 0;

};

} // namespace segment_v2

} // namespace doris