Method buildQueryPlan

src/Interpreters/InterpreterSelectQuery.cpp:745–801

}

void InterpreterSelectQuery::buildQueryPlan(QueryPlan & query_plan)
{
    std::shared_ptr<InterpreterPerfectShard> interpreter_perfect_shard
        = context->getSettingsRef().distributed_perfect_shard ? std::make_shared<InterpreterPerfectShard>(*this) : nullptr;

    if (interpreter_perfect_shard && interpreter_perfect_shard->checkPerfectShardable())
    {
        interpreter_perfect_shard->buildQueryPlan(query_plan);
    }
    else
        executeImpl(query_plan, input, std::move(input_pipe));

    /// We must guarantee that result structure is the same as in getSampleBlock()
    ///
    /// But if it's a projection query, plan header does not match result_header.
    /// TODO: add special stage for InterpreterSelectQuery?
    if (!options.is_projection_query && !blocksHaveEqualStructure(query_plan.getCurrentDataStream().header, result_header))
    {
        auto convert_actions_dag = ActionsDAG::makeConvertingActions(
            query_plan.getCurrentDataStream().header.getColumnsWithTypeAndName(),
            result_header.getColumnsWithTypeAndName(),
            ActionsDAG::MatchColumnsMode::Name,
            true);

        auto converting = std::make_unique<ExpressionStep>(query_plan.getCurrentDataStream(), convert_actions_dag);
        query_plan.addStep(std::move(converting));
    }

    if (context->getSettingsRef().enable_final_sample)
    {
        auto & query = getSelectQuery();
        if (query.sampleSize())
        {
            ASTSampleRatio * sample = query.sampleSize()->as<ASTSampleRatio>();
            ASTSampleRatio::BigNum numerator = sample->ratio.numerator;
            ASTSampleRatio::BigNum denominator = sample->ratio.denominator;
            if (numerator <= 1 || denominator > 1)
                return;

            auto sampling
                = std::make_unique<FinalSampleStep>(query_plan.getCurrentDataStream(), numerator, context->getSettingsRef().max_block_size);
            query_plan.addStep(std::move(sampling));
        }
    }

    if (!table_id.empty())
        addUsedStorageID(table_id);
    if (has_join)
        setHasAllUsedStorageIDs(false);

    if (interpreter_subquery)
    {
        addUsedStorageIDs(interpreter_subquery->getUsedStorageIDs());
        if (!interpreter_subquery->hasAllUsedStorageIDs())
            setHasAllUsedStorageIDs(false);
    }
}