Function buildSelectQueryPlan

src/Processors/QueryPlan/ReadFromLoopStep.cpp:45–87

Build a query plan by constructing a synthetic SELECT query and running it through the interpreter. The FROM clause is either a catalog table (database.table) or a table function AST — exactly one of the two must be provided.

    /// the interpreter. The FROM clause is either a catalog table (database.table) or a
    /// table function AST — exactly one of the two must be provided.
    void buildSelectQueryPlan(
        QueryPlan & plan,
        const Names & column_names,
        const SelectQueryInfo & query_info,
        ContextPtr context,
        const String & database = {},
        const String & table = {},
        const ASTPtr & table_function_ast = nullptr)
    {
        auto select_query = make_intrusive<ASTSelectQuery>();

        auto select_expr_list = make_intrusive<ASTExpressionList>();
        for (const auto & col_name : column_names)
            select_expr_list->children.push_back(make_intrusive<ASTIdentifier>(col_name));
        select_query->setExpression(ASTSelectQuery::Expression::SELECT, std::move(select_expr_list));

        if (table_function_ast)
            select_query->addTableFunction(table_function_ast);
        else
            select_query->replaceDatabaseAndTable(database, table);

        auto select_ast = make_intrusive<ASTSelectWithUnionQuery>();
        select_ast->list_of_selects = make_intrusive<ASTExpressionList>();
        select_ast->list_of_selects->children.push_back(select_query);
        select_ast->children.push_back(select_ast->list_of_selects);

        auto options = SelectQueryOptions(QueryProcessingStage::Complete, 0, false);

        if (context->getSettingsRef()[Setting::allow_experimental_analyzer])
        {
            InterpreterSelectQueryAnalyzer interpreter(select_ast, context, options, column_names);
            if (query_info.storage_limits)
                interpreter.addStorageLimits(*query_info.storage_limits);
            plan = std::move(interpreter).extractQueryPlan();
        }
        else
        {
            InterpreterSelectWithUnionQuery interpreter(select_ast, context, options, column_names);
            if (query_info.storage_limits)
                interpreter.addStorageLimits(*query_info.storage_limits);
            interpreter.buildQueryPlan(plan);
        }
    }
}

class LoopSource : public ISource