Method explainUsingOptimizer

src/Interpreters/InterpreterExplainQuery.cpp:647–713

}

BlockInputStreamPtr InterpreterExplainQuery::explainUsingOptimizer()
{
    WriteBufferFromOwnString buffer;
    bool single_line = false;
    const auto & explain = query->as<ASTExplainQuery &>();
    auto context = getContext();

    if (explain.getKind() == ASTExplainQuery::AnalyzedSyntax)
    {
        if (explain.getSettings())
            throw Exception("Settings are not supported for EXPLAIN SYNTAX query.", ErrorCodes::UNKNOWN_SETTING);

        auto query_ptr = explain.getExplainedQuery();
        query_ptr = QueryRewriter().rewrite(query_ptr, context);
        query_ptr->format(IAST::FormatSettings(buffer, false));
    }
    else if (explain.getKind() == ASTExplainQuery::TraceOptimizer || explain.getKind() == ASTExplainQuery::TraceOptimizerRule)
    {
        if (explain.getSettings())
            throw Exception("Settings are not supported for EXPLAIN TRACE OPTIMIZER query.", ErrorCodes::UNKNOWN_SETTING);

        context->initOptimizerProfile();
        try
        {
            InterpreterSelectQueryUseOptimizer interpreter(explain.getExplainedQuery(), context, SelectQueryOptions());
            interpreter.getPlanSegment();
        }
        catch (...)
        {
            context->clearOptimizerProfile();
            throw;
        }

        if (explain.getKind() == ASTExplainQuery::TraceOptimizerRule)
            buffer << context->getOptimizerProfile(true);
        else
            buffer << context->getOptimizerProfile();
    }
    else
    {
        InterpreterSelectQueryUseOptimizer interpreter(explain.getExplainedQuery(), context, SelectQueryOptions());
        auto query_plan = interpreter.getQueryPlan();
        if (explain.getKind() == ASTExplainQuery::ExplainKind::OptimizerPlan
            || explain.getKind() == ASTExplainQuery::ExplainKind::QueryPlan)
        {
            explainPlanWithOptimizer(explain, *query_plan, buffer, context, single_line);
        }
        else if (explain.getKind() == ASTExplainQuery::ExplainKind::Distributed)
        {
            explainDistributedWithOptimizer(explain, *query_plan, buffer, context);
        }
        else if (explain.getKind() == ASTExplainQuery::ExplainKind::QueryPipeline)
        {
            explainPipelineWithOptimizer(explain, *query_plan, buffer, context);
        }
    }

    Block sample_block = getSampleBlock();