Method buildExecutePlan

src/QueryPlan/TableScanStep.cpp:350–475

}

ExecutePlan TableScanExecutor::buildExecutePlan(const DistributedPipelineSettings & distributed_settings)
{
    if (!match_projection)
        return {};

    PartGroups part_groups;
    {
        auto parts = storage.getDataPartsVector();
        if (distributed_settings.source_task_index && distributed_settings.source_task_count)
        {
            auto size_before_filtering = parts.size();
            filterParts(parts, distributed_settings.source_task_index.value(), distributed_settings.source_task_count.value());
            LOG_TRACE(
                log,
                "After filtering(index:{}, count:{}) the number of parts of table {} becomes {} from {}",
                distributed_settings.source_task_index.value(),
                distributed_settings.source_task_count.value(),
                storage.getTableName(),
                parts.size(),
                size_before_filtering);
        }
        parts.erase(std::remove_if(parts.begin(), parts.end(), [](auto & part) { return part->info.isFakeDropRangePart(); }), parts.end());

        LOG_DEBUG(log, "Num of parts before part pruning: {}", std::to_string(parts.size()));

        prunePartsByIndex(parts);

        LOG_DEBUG(log, "Num of parts after part pruning: {}", std::to_string(parts.size()));

        if (parts.size() > 100000)
            throw Exception(ErrorCodes::PROJECTION_SELECTION_ERROR, "Projection selection error: too many parts before part grouping");

        part_groups = groupPartsBySchema(parts);

        LOG_DEBUG(log, "Num of part groups before part grouping: {}", std::to_string(part_groups.size()));

        if (part_groups.size() > 100)
            throw Exception(ErrorCodes::PROJECTION_SELECTION_ERROR, "Projection selection error: Too many part groups before projection selection");
    }

    ExecutePlan execute_plan;
    auto table_columns = storage_metadata->getColumns().getAllPhysical();

    for (auto & part_group: part_groups)
    {
        ProjectionMatchContexts projection_candidates;

        // collect qualified projection candidate
        for (const auto & projection_desc: storage_metadata->projections)
            if (part_group.hasProjection(projection_desc.name))
            {
                projection_candidates.emplace_back(projection_desc, part_group, &storage, table_columns);
                if (!match(projection_candidates.back()))
                    projection_candidates.pop_back();
            }

        // select best projection by marks to read
        ProjectionMatchContext * selected_candidate = nullptr;