Method prepareColumnNamesAndTypes

src/WorkerTasks/MergeTreeDataMerger.cpp:137–214

}

void MergeTreeDataMerger::prepareColumnNamesAndTypes(
    const StorageSnapshotPtr & storage_snapshot,
    const MergeTreeMetaBase::MergingParams & merging_params,
    Names & all_column_names,
    Names & gathering_column_names,
    Names & merging_column_names,
    NamesAndTypesList & storage_columns,
    NamesAndTypesList & gathering_columns,
    NamesAndTypesList & merging_columns)
{
    auto metadata_snapshot = storage_snapshot->metadata;
    all_column_names = metadata_snapshot->getColumns().getNamesOfPhysical();
    storage_columns = metadata_snapshot->getColumns().getAllPhysical();

    extendObjectColumns(storage_columns, storage_snapshot->object_columns, false);

    Names sort_key_columns_vec = metadata_snapshot->getSortingKey().expression->getRequiredColumns();
    std::set<String> key_columns(sort_key_columns_vec.cbegin(), sort_key_columns_vec.cend());
    for (const auto & index : metadata_snapshot->getSecondaryIndices())
    {
        Names index_columns_vec = index.expression->getRequiredColumns();
        std::copy(index_columns_vec.cbegin(), index_columns_vec.cend(), std::inserter(key_columns, key_columns.end()));
    }

    for (const auto & projection : metadata_snapshot->getProjections())
    {
        Names projection_columns_vec = projection.required_columns;
        std::copy(projection_columns_vec.cbegin(), projection_columns_vec.cend(), std::inserter(key_columns, key_columns.end()));
    }

    /// Force unique key columns and extra column for Unique mode,
    /// otherwise MergedBlockOutputStream won't have the required columns to generate unique key index file.
    if (metadata_snapshot->hasUniqueKey())
    {
        auto unique_key_expr = metadata_snapshot->getUniqueKey().expression;
        if (!unique_key_expr)
            throw Exception("Missing unique key expression for Unique mode", ErrorCodes::LOGICAL_ERROR);

        Names index_columns_vec = unique_key_expr->getRequiredColumns();
        std::copy(index_columns_vec.cbegin(), index_columns_vec.cend(), std::inserter(key_columns, key_columns.end()));

        /// also need version column when building unique key index file
        if (merging_params.hasExplicitVersionColumn())
            key_columns.insert(merging_params.version_column);
    }

    /// Force sign column for Collapsing mode
    if (merging_params.mode == MergeTreeMetaBase::MergingParams::Collapsing)
        key_columns.emplace(merging_params.sign_column);

    /// Force version column for Replacing mode
    if (merging_params.mode == MergeTreeMetaBase::MergingParams::Replacing)
        key_columns.emplace(merging_params.version_column);

    /// Force sign column for VersionedCollapsing mode. Version is already in primary key.
    if (merging_params.mode == MergeTreeMetaBase::MergingParams::VersionedCollapsing)
        key_columns.emplace(merging_params.sign_column);