[Feature] Support assign sort key of primary key model by schema chan…

…ge reorder. (#13642) (#14930)

* [cherry-pick][branch-2.5][Feature] Support assign sort key of primary key model by schema change reorder. (#13642)

``
MySQL [test]> CREATE TABLE test (
    ->   `k1` int,
    ->   `k2` int,
    ->   `k3` int,
    ->   `v1` int,
    ->   `v2` int,
    ->   `v3` int,
    ->   `v4` int,
    ->   `v5` int
    -> ) ENGINE=OLAP
    -> PRIMARY KEY(`k1`, `k2`, `k3`)
    -> COMMENT "OLAP"
    -> DISTRIBUTED BY HASH(`k1`, `k2`, `k3`) BUCKETS 1
    -> ORDER BY(`v2`, `v3`)
    -> PROPERTIES ("replication_num" = "1");
Query OK, 0 rows affected (0.11 sec)

MySQL [test]> ALTER TABLE test ORDER BY (v3, v2);
Primary key table do not support reorder column
```
should be:
```
MySQL [test]> select v2, v3 from test;
+------+------+
| v2   | v3   |
+------+------+
|    1 |    5 |
|    2 |    4 |
|    3 |    3 |
|    4 |    2 |
|    5 |    1 |
+------+------+
5 rows in set (0.02 sec)

MySQL [test]> show create table test;
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| test  | CREATE TABLE `test` (
  `k1` int(11) NOT NULL COMMENT "",
  `k2` int(11) NOT NULL COMMENT "",
  `k3` int(11) NOT NULL COMMENT "",
  `v1` int(11) NULL COMMENT "",
  `v2` int(11) NULL COMMENT "",
  `v3` int(11) NULL COMMENT "",
  `v4` int(11) NULL COMMENT "",
  `v5` int(11) NULL COMMENT ""
) ENGINE=OLAP
PRIMARY KEY(`k1`, `k2`, `k3`)
COMMENT "OLAP"
DISTRIBUTED BY HASH(`k1`, `k2`, `k3`) BUCKETS 1
ORDER BY(`v2`, `v3`)
PROPERTIES (
"replication_num" = "1",
"in_memory" = "false",
"storage_format" = "DEFAULT",
"enable_persistent_index" = "false",
"compression" = "LZ4"
); |
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)

MySQL [test]> ALTER TABLE test ORDER BY (v3, v2);
Query OK, 0 rows affected (0.03 sec)

MySQL [test]> select v3, v2 from test;
+------+------+
| v3   | v2   |
+------+------+
|    1 |    5 |
|    2 |    4 |
|    3 |    3 |
|    4 |    2 |
|    5 |    1 |
+------+------+
5 rows in set (0.01 sec)

MySQL [test]> show create table test;
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| test  | CREATE TABLE `test` (
  `k1` int(11) NOT NULL COMMENT "",
  `k2` int(11) NOT NULL COMMENT "",
  `k3` int(11) NOT NULL COMMENT "",
  `v1` int(11) NULL COMMENT "",
  `v2` int(11) NULL COMMENT "",
  `v3` int(11) NULL COMMENT "",
  `v4` int(11) NULL COMMENT "",
  `v5` int(11) NULL COMMENT ""
) ENGINE=OLAP
PRIMARY KEY(`k1`, `k2`, `k3`)
COMMENT "OLAP"
DISTRIBUTED BY HASH(`k1`, `k2`, `k3`) BUCKETS 1
ORDER BY(`v3`, `v2`)
PROPERTIES (
"replication_num" = "1",
"in_memory" = "false",
"storage_format" = "DEFAULT",
"enable_persistent_index" = "false",
"compression" = "LZ4"
); |
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)
```

* resolve conflict.

be/src/storage/rowset/rowset_writer.cpp

@@ -580,7 +580,8 @@ Status HorizontalRowsetWriter::_final_merge() {
         ChunkIteratorPtr itr;
         // create temporary segment files at first, then merge them and create final segment files if schema change with sorting
         if (_context.schema_change_sorting) {
-            if (_context.tablet_schema->keys_type() == KeysType::DUP_KEYS) {
+            if (_context.tablet_schema->keys_type() == KeysType::DUP_KEYS ||
+                _context.tablet_schema->keys_type() == KeysType::PRIMARY_KEYS) {
                 itr = new_heap_merge_iterator(seg_iterators);
             } else if (_context.tablet_schema->keys_type() == KeysType::UNIQUE_KEYS ||
                        _context.tablet_schema->keys_type() == KeysType::AGG_KEYS) {
@@ -677,7 +678,8 @@ Status HorizontalRowsetWriter::_final_merge() {
             ChunkIteratorPtr itr;
             // create temporary segment files at first, then merge them and create final segment files if schema change with sorting
             if (_context.schema_change_sorting) {
-                if (_context.tablet_schema->keys_type() == KeysType::DUP_KEYS) {
+                if (_context.tablet_schema->keys_type() == KeysType::DUP_KEYS ||
+                    _context.tablet_schema->keys_type() == KeysType::PRIMARY_KEYS) {
                     itr = new_mask_merge_iterator(seg_iterators, mask_buffer.get());
                 } else if (_context.tablet_schema->keys_type() == KeysType::UNIQUE_KEYS ||
                            _context.tablet_schema->keys_type() == KeysType::AGG_KEYS) {
@@ -747,7 +749,8 @@ Status HorizontalRowsetWriter::_final_merge() {
         ChunkIteratorPtr itr;
         // create temporary segment files at first, then merge them and create final segment files if schema change with sorting
         if (_context.schema_change_sorting) {
-            if (_context.tablet_schema->keys_type() == KeysType::DUP_KEYS) {
+            if (_context.tablet_schema->keys_type() == KeysType::DUP_KEYS ||
+                _context.tablet_schema->keys_type() == KeysType::PRIMARY_KEYS) {
                 itr = new_heap_merge_iterator(seg_iterators);
             } else if (_context.tablet_schema->keys_type() == KeysType::UNIQUE_KEYS ||
                        _context.tablet_schema->keys_type() == KeysType::AGG_KEYS) {

be/src/storage/schema_change.cpp

@@ -58,18 +58,6 @@ int compare_chunk_row(const ChunkRow& lhs, const ChunkRow& rhs) {
     return 0;
 }
 
-class ChunkSorter {
-public:
-    explicit ChunkSorter(ChunkAllocator* allocator);
-    virtual ~ChunkSorter();
-
-    bool sort(ChunkPtr& chunk, const TabletSharedPtr& new_tablet);
-
-private:
-    ChunkPtr _swap_chunk;
-    size_t _max_allocated_rows{0};
-};
-
 // TODO: optimize it with vertical sort
 class ChunkMerger {
 public:
@@ -115,14 +103,23 @@ bool ChunkSorter::sort(ChunkPtr& chunk, const TabletSharedPtr& new_tablet) {
 
     _swap_chunk->reset();
 
+    std::vector<ColumnId> sort_key_idxes;
+    if (new_schema.sort_key_idxes().empty()) {
+        int num_key_columns = chunk->schema()->num_key_fields();
+        for (ColumnId i = 0; i < num_key_columns; ++i) {
+            sort_key_idxes.push_back(i);
+        }
+    } else {
+        sort_key_idxes = new_schema.sort_key_idxes();
+    }
     Columns key_columns;
-    int num_key_columns = chunk->schema()->num_key_fields();
-    for (int i = 0; i < num_key_columns; i++) {
-        key_columns.push_back(chunk->get_column_by_index(i));
+    for (const auto sort_key_idx : sort_key_idxes) {
+        key_columns.push_back(chunk->get_column_by_index(sort_key_idx));
     }
 
     SmallPermutation perm = create_small_permutation(chunk->num_rows());
-    Status st = stable_sort_and_tie_columns(false, key_columns, SortDescs::asc_null_first(num_key_columns), &perm);
+    Status st =
+            stable_sort_and_tie_columns(false, key_columns, SortDescs::asc_null_first(sort_key_idxes.size()), &perm);
     CHECK(st.ok());
     std::vector<uint32_t> selective;
     permutate_to_selective(perm, &selective);
@@ -761,12 +758,17 @@ Status SchemaChangeHandler::_do_process_alter_tablet_v2(const TAlterTabletReqV2&
     }
 
     if (base_tablet->keys_type() == KeysType::PRIMARY_KEYS) {
+        const auto& base_sort_key_idxes = base_tablet->tablet_schema().sort_key_idxes();
+        const auto& new_sort_key_idxes = new_tablet->tablet_schema().sort_key_idxes();
+        if (std::mismatch(new_sort_key_idxes.begin(), new_sort_key_idxes.end(), base_sort_key_idxes.begin()).first !=
+            new_sort_key_idxes.end()) {
+            sc_params.sc_directly = !(sc_params.sc_sorting = true);
+        }
         if (sc_params.sc_directly) {
             status = new_tablet->updates()->convert_from(base_tablet, request.alter_version,
                                                          sc_params.chunk_changer.get());
         } else if (sc_params.sc_sorting) {
-            LOG(WARNING) << "schema change of primary key model do not support sorting.";
-            status = Status::NotSupported("schema change of primary key model do not support sorting.");
+            status = new_tablet->updates()->reorder_from(base_tablet, request.alter_version);
         } else {
             status = new_tablet->updates()->link_from(base_tablet.get(), request.alter_version);
         }

be/src/storage/schema_change.h

@@ -59,6 +59,19 @@ class ChunkAllocator {
     size_t _memory_limitation;
 };
 
+class ChunkSorter {
+public:
+    explicit ChunkSorter(ChunkAllocator* allocator);
+    virtual ~ChunkSorter();
+
+    bool sort(ChunkPtr& chunk, const TabletSharedPtr& new_tablet);
+
+private:
+    ChunkAllocator* _chunk_allocator = nullptr;
+    ChunkPtr _swap_chunk;
+    size_t _max_allocated_rows;
+};
+
 class SchemaChange {
 public:
     SchemaChange() = default;
@@ -116,10 +129,10 @@ class SchemaChangeWithSorting : public SchemaChange {
     Status process_v2(TabletReader* reader, RowsetWriter* new_rowset_writer, TabletSharedPtr new_tablet,
                       TabletSharedPtr base_tablet, RowsetSharedPtr rowset) override;
 
-private:
     static bool _internal_sorting(std::vector<ChunkPtr>& chunk_arr, RowsetWriter* new_rowset_writer,
                                   TabletSharedPtr tablet);
 
+private:
     ChunkChanger* _chunk_changer = nullptr;
     size_t _memory_limitation;
     ChunkAllocator* _chunk_allocator = nullptr;

be/src/storage/tablet_updates.cpp

@@ -20,6 +20,7 @@
 #include "storage/chunk_iterator.h"
 #include "storage/compaction_utils.h"
 #include "storage/del_vector.h"
+#include "storage/merge_iterator.h"
 #include "storage/rowset/default_value_column_iterator.h"
 #include "storage/rowset/rowset_factory.h"
 #include "storage/rowset/rowset_meta_manager.h"
@@ -2693,6 +2694,220 @@ Status TabletUpdates::_convert_from_base_rowset(const std::shared_ptr<Tablet>& b
     return rowset_writer->flush();
 }
 
+Status TabletUpdates::reorder_from(const std::shared_ptr<Tablet>& base_tablet, int64_t request_version) {
+    OlapStopWatch watch;
+    DCHECK(_tablet.tablet_state() == TABLET_NOTREADY)
+            << "tablet state is not TABLET_NOTREADY, reorder_from is not allowed"
+            << " tablet_id:" << _tablet.tablet_id() << " tablet_state:" << _tablet.tablet_state();
+    LOG(INFO) << "reorder_from start tablet:" << _tablet.tablet_id() << " #pending:" << _pending_commits.size()
+              << " base_tablet:" << base_tablet->tablet_id() << " request_version:" << request_version;
+    int64_t max_version = base_tablet->updates()->max_version();
+    if (max_version < request_version) {
+        LOG(WARNING) << "reorder_from: base_tablet's max_version:" << max_version
+                     << " < alter_version:" << request_version << " tablet:" << _tablet.tablet_id()
+                     << " base_tablet:" << base_tablet->tablet_id();
+        return Status::InternalError("reorder_from: max_version < request_version");
+    }
+    std::vector<RowsetSharedPtr> src_rowsets;
+    EditVersion version;
+    Status status = base_tablet->updates()->get_applied_rowsets(request_version, &src_rowsets, &version);
+    if (!status.ok()) {
+        LOG(WARNING) << "reorder_from: get base tablet rowsets error tablet:" << base_tablet->tablet_id()
+                     << " request_version:" << request_version << " reason:" << status;
+        return status;
+    }
+
+    // disable compaction temporarily when tablet just loaded
+    _last_compaction_time_ms = UnixMillis();
+
+    auto kv_store = _tablet.data_dir()->get_meta();
+    auto tablet_id = _tablet.tablet_id();
+    uint32_t next_rowset_id = 0;
+    std::vector<RowsetLoadInfo> new_rowset_load_infos(src_rowsets.size());
+
+    std::vector<vectorized::ChunkPtr> chunk_arr;
+
+    vectorized::Schema base_schema = ChunkHelper::convert_schema_to_format_v2(base_tablet->tablet_schema());
+    vectorized::ChunkSorter chunk_sorter(_chunk_allocator);
+
+    OlapReaderStatistics stats;
+
+    size_t total_bytes = 0;
+    size_t total_rows = 0;
+    size_t total_files = 0;
+    for (int i = 0; i < src_rowsets.size(); i++) {
+        const auto& src_rowset = src_rowsets[i];
+
+        RowsetReleaseGuard guard(src_rowset->shared_from_this());
+        auto res = src_rowset->get_segment_iterators2(base_schema, base_tablet->data_dir()->get_meta(), version.major(),
+                                                      &stats);
+        if (!res.ok()) {
+            return res.status();
+        }
+        const auto& seg_iterators = res.value();
+
+        RowsetId rid = StorageEngine::instance()->next_rowset_id();
+
+        RowsetWriterContext writer_context;
+        writer_context.rowset_id = rid;
+        writer_context.tablet_uid = _tablet.tablet_uid();
+        writer_context.tablet_id = _tablet.tablet_id();
+        writer_context.partition_id = _tablet.partition_id();
+        writer_context.tablet_schema_hash = _tablet.schema_hash();
+        writer_context.rowset_path_prefix = _tablet.schema_hash_path();
+        writer_context.tablet_schema = &_tablet.tablet_schema();
+        writer_context.rowset_state = VISIBLE;
+        writer_context.version = src_rowset->version();
+        writer_context.segments_overlap = src_rowset->rowset_meta()->segments_overlap();
+        writer_context.schema_change_sorting = true;
+
+        std::unique_ptr<RowsetWriter> rowset_writer;
+        status = RowsetFactory::create_rowset_writer(writer_context, &rowset_writer);
+        if (!status.ok()) {
+            LOG(INFO) << "build rowset writer failed";
+            return Status::InternalError("build rowset writer failed");
+        }
+
+        vectorized::ChunkPtr base_chunk = ChunkHelper::new_chunk(base_schema, config::vector_chunk_size);
+
+        vectorized::Schema new_schema = ChunkHelper::convert_schema_to_format_v2(_tablet.tablet_schema());
+        vectorized::ChunkPtr new_chunk = ChunkHelper::new_chunk(new_schema, config::vector_chunk_size);
+
+        for (auto& seg_iterator : seg_iterators) {
+            if (seg_iterator.get() == nullptr) {
+                continue;
+            }
+            while (true) {
+                base_chunk->reset();
+                Status status = seg_iterator->get_next(base_chunk.get());
+                if (!status.ok()) {
+                    if (status.is_end_of_file()) {
+                        break;
+                    } else {
+                        std::stringstream ss;
+                        ss << "segment iterator failed to get next chunk, status is:" << status.to_string();
+                        LOG(WARNING) << ss.str();
+                        return Status::InternalError(ss.str());
+                    }
+                }
+
+                for (auto i = 0; i < base_chunk->num_columns(); ++i) {
+                    base_chunk->get_column_by_index(i)->swap_column(*new_chunk->get_column_by_index(i));
+                }
+
+                total_bytes += static_cast<double>(new_chunk->memory_usage());
+                total_rows += static_cast<double>(new_chunk->num_rows());
+
+                if (new_chunk->num_rows() > 0) {
+                    if (!chunk_sorter.sort(new_chunk, std::static_pointer_cast<Tablet>(_tablet.shared_from_this()))) {
+                        LOG(WARNING) << "chunk data sort failed";
+                        return Status::InternalError("chunk data sort failed");
+                    }
+                }
+                chunk_arr.push_back(new_chunk);
+            }
+        }
+
+        if (!chunk_arr.empty()) {
+            if (!vectorized::SchemaChangeWithSorting::_internal_sorting(
+                        chunk_arr, rowset_writer.get(), std::static_pointer_cast<Tablet>(_tablet.shared_from_this()))) {
+                return Status::InternalError("failed to sorting internally.");
+            }
+        }
+
+        status = rowset_writer->flush();
+        if (!status.ok()) {
+            LOG(WARNING) << "failed to convert from base rowset, exit alter process";
+            return status;
+        }
+
+        auto new_rowset = rowset_writer->build();
+        if (!new_rowset.ok()) return new_rowset.status();
+
+        auto& new_rowset_load_info = new_rowset_load_infos[i];
+        new_rowset_load_info.num_segments = (*new_rowset)->num_segments();
+        new_rowset_load_info.rowset_id = next_rowset_id;
+
+        auto& rowset_meta_pb = new_rowset_load_info.rowset_meta_pb;
+        (*new_rowset)->rowset_meta()->to_rowset_pb(&rowset_meta_pb);
+        rowset_meta_pb.set_rowset_seg_id(new_rowset_load_info.rowset_id);
+        rowset_meta_pb.set_rowset_id(rid.to_string());
+
+        next_rowset_id += std::max(1U, (uint32_t)new_rowset_load_info.num_segments);
+
+        total_bytes += rowset_meta_pb.total_disk_size();
+        total_rows += rowset_meta_pb.num_rows();
+        total_files += rowset_meta_pb.num_segments() + rowset_meta_pb.num_delete_files();
+    }
+
+    TabletMetaPB meta_pb;
+    _tablet.tablet_meta()->to_meta_pb(&meta_pb);
+    meta_pb.set_tablet_state(TabletStatePB::PB_RUNNING);
+    TabletUpdatesPB* updates_pb = meta_pb.mutable_updates();
+    updates_pb->clear_versions();
+    auto version_pb = updates_pb->add_versions();
+    version_pb->mutable_version()->set_major(version.major());
+    version_pb->mutable_version()->set_minor(version.minor());
+    int64_t creation_time = time(nullptr);
+    version_pb->set_creation_time(creation_time);
+    for (auto& new_rowset_load_info : new_rowset_load_infos) {
+        version_pb->mutable_rowsets()->Add(new_rowset_load_info.rowset_id);
+    }
+    version_pb->set_rowsetid_add(next_rowset_id);
+    auto apply_version_pb = updates_pb->mutable_apply_version();
+    apply_version_pb->set_major(version.major());
+    apply_version_pb->set_minor(version.minor());
+    updates_pb->set_next_log_id(1);
+    updates_pb->set_next_rowset_id(next_rowset_id);
+
+    // delete old meta & write new meta
+    auto data_dir = _tablet.data_dir();
+    rocksdb::WriteBatch wb;
+    RETURN_IF_ERROR(TabletMetaManager::clear_log(data_dir, &wb, tablet_id));
+    RETURN_IF_ERROR(TabletMetaManager::clear_rowset(data_dir, &wb, tablet_id));
+    RETURN_IF_ERROR(TabletMetaManager::clear_del_vector(data_dir, &wb, tablet_id));
+    RETURN_IF_ERROR(TabletMetaManager::clear_persistent_index(data_dir, &wb, tablet_id));
+    // do not clear pending rowsets, because these pending rowsets should be committed after schemachange is done
+    RETURN_IF_ERROR(TabletMetaManager::put_tablet_meta(data_dir, &wb, meta_pb));
+    DelVector delvec;
+    for (const auto& new_rowset_load_info : new_rowset_load_infos) {
+        RETURN_IF_ERROR(
+                TabletMetaManager::put_rowset_meta(data_dir, &wb, tablet_id, new_rowset_load_info.rowset_meta_pb));
+        for (int j = 0; j < new_rowset_load_info.num_segments; j++) {
+            RETURN_IF_ERROR(TabletMetaManager::put_del_vector(data_dir, &wb, tablet_id,
+                                                              new_rowset_load_info.rowset_id + j, delvec));
+        }
+    }
+
+    std::unique_lock wrlock(_tablet.get_header_lock());
+    status = kv_store->write_batch(&wb);
+    if (!status.ok()) {
+        LOG(WARNING) << "Fail to delete old meta and write new meta" << tablet_id << ": " << status;
+        return Status::InternalError("Fail to delete old meta and write new meta");
+    }
+
+    auto update_manager = StorageEngine::instance()->update_manager();
+    auto index_entry = update_manager->index_cache().get_or_create(tablet_id);
+    index_entry->update_expire_time(MonotonicMillis() + update_manager->get_cache_expire_ms());
+    auto& index = index_entry->value();
+    index.unload();
+    update_manager->index_cache().release(index_entry);
+    // 4. load from new meta
+    status = _load_from_pb(*updates_pb);
+    if (!status.ok()) {
+        LOG(WARNING) << "_load_from_pb failed tablet_id:" << tablet_id << " " << status;
+        return status;
+    }
+
+    _tablet.set_tablet_state(TabletState::TABLET_RUNNING);
+    LOG(INFO) << "reorder_from finish tablet:" << _tablet.tablet_id() << " version:" << this->max_version()
+              << " base tablet:" << base_tablet->tablet_id() << " #pending:" << _pending_commits.size()
+              << " time:" << watch.get_elapse_second() << "s"
+              << " #column:" << _tablet.tablet_schema().num_columns() << " #rowset:" << src_rowsets.size()
+              << " #file:" << total_files << " #row:" << total_rows << " bytes:" << total_bytes;
+    return Status::OK();
+}
+
 void TabletUpdates::_remove_unused_rowsets() {
     size_t removed = 0;
     std::vector<RowsetSharedPtr> skipped_rowsets;

be/src/storage/tablet_updates.h

@@ -36,6 +36,7 @@ class Schema;
 class TabletReader;
 class ChunkChanger;
 class SegmentIterator;
+class ChunkAllocator;
 } // namespace vectorized
 
 struct CompactionInfo {
@@ -163,6 +164,8 @@ class TabletUpdates {
     Status convert_from(const std::shared_ptr<Tablet>& base_tablet, int64_t request_version,
                         vectorized::ChunkChanger* chunk_changer);
 
+    Status reorder_from(const std::shared_ptr<Tablet>& base_tablet, int64_t request_version);
+
     Status load_snapshot(const SnapshotMeta& snapshot_meta, bool restore_from_backup = false);
 
     Status get_latest_applied_version(EditVersion* latest_applied_version);
@@ -408,6 +411,8 @@ class TabletUpdates {
     std::atomic<bool> _error{false};
     std::string _error_msg;
 
+    vectorized::ChunkAllocator* _chunk_allocator = nullptr;
+
     TabletUpdates(const TabletUpdates&) = delete;
     const TabletUpdates& operator=(const TabletUpdates&) = delete;
 };