#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include namespace DB { namespace ErrorCodes { extern const int TOO_DEEP_SUBQUERIES; extern const int SAMPLING_NOT_SUPPORTED; extern const int ILLEGAL_FINAL; extern const int ILLEGAL_PREWHERE; extern const int TOO_MANY_COLUMNS; extern const int LOGICAL_ERROR; extern const int NOT_IMPLEMENTED; extern const int PARAMETER_OUT_OF_BOUND; extern const int INVALID_LIMIT_EXPRESSION; extern const int INVALID_WITH_FILL_EXPRESSION; extern const int ACCESS_DENIED; } /// Assumes `storage` is set and the table filter (row-level security) is not empty. String InterpreterSelectQuery::generateFilterActions( ActionsDAGPtr & actions, const ASTPtr & row_policy_filter, const Names & prerequisite_columns) const { const auto & db_name = table_id.getDatabaseName(); const auto & table_name = table_id.getTableName(); /// TODO: implement some AST builders for this kind of stuff ASTPtr query_ast = std::make_shared(); auto * select_ast = query_ast->as(); select_ast->setExpression(ASTSelectQuery::Expression::SELECT, std::make_shared()); auto expr_list = select_ast->select(); // The first column is our filter expression. expr_list->children.push_back(row_policy_filter); /// Keep columns that are required after the filter actions. for (const auto & column_str : prerequisite_columns) { ParserExpression expr_parser; expr_list->children.push_back(parseQuery(expr_parser, column_str, 0, context->getSettingsRef().max_parser_depth)); } select_ast->setExpression(ASTSelectQuery::Expression::TABLES, std::make_shared()); auto tables = select_ast->tables(); auto tables_elem = std::make_shared(); auto table_expr = std::make_shared(); tables->children.push_back(tables_elem); tables_elem->table_expression = table_expr; tables_elem->children.push_back(table_expr); table_expr->database_and_table_name = createTableIdentifier(db_name, table_name); table_expr->children.push_back(table_expr->database_and_table_name); /// Using separate expression analyzer to prevent any possible alias injection auto syntax_result = TreeRewriter(*context).analyzeSelect(query_ast, TreeRewriterResult({}, storage, metadata_snapshot)); SelectQueryExpressionAnalyzer analyzer(query_ast, syntax_result, *context, metadata_snapshot); actions = analyzer.simpleSelectActions(); return expr_list->children.at(0)->getColumnName(); } InterpreterSelectQuery::InterpreterSelectQuery( const ASTPtr & query_ptr_, const Context & context_, const SelectQueryOptions & options_, const Names & required_result_column_names_) : InterpreterSelectQuery(query_ptr_, context_, nullptr, std::nullopt, nullptr, options_, required_result_column_names_) { } InterpreterSelectQuery::InterpreterSelectQuery( const ASTPtr & query_ptr_, const Context & context_, const BlockInputStreamPtr & input_, const SelectQueryOptions & options_) : InterpreterSelectQuery(query_ptr_, context_, input_, std::nullopt, nullptr, options_.copy().noSubquery()) {} InterpreterSelectQuery::InterpreterSelectQuery( const ASTPtr & query_ptr_, const Context & context_, Pipe input_pipe_, const SelectQueryOptions & options_) : InterpreterSelectQuery(query_ptr_, context_, nullptr, std::move(input_pipe_), nullptr, options_.copy().noSubquery()) {} InterpreterSelectQuery::InterpreterSelectQuery( const ASTPtr & query_ptr_, const Context & context_, const StoragePtr & storage_, const StorageMetadataPtr & metadata_snapshot_, const SelectQueryOptions & options_) : InterpreterSelectQuery(query_ptr_, context_, nullptr, std::nullopt, storage_, options_.copy().noSubquery(), {}, metadata_snapshot_) {} InterpreterSelectQuery::~InterpreterSelectQuery() = default; /** There are no limits on the maximum size of the result for the subquery. * Since the result of the query is not the result of the entire query. */ static Context getSubqueryContext(const Context & context) { Context subquery_context = context; Settings subquery_settings = context.getSettings(); subquery_settings.max_result_rows = 0; subquery_settings.max_result_bytes = 0; /// The calculation of extremes does not make sense and is not necessary (if you do it, then the extremes of the subquery can be taken for whole query). subquery_settings.extremes = false; subquery_context.setSettings(subquery_settings); return subquery_context; } static void rewriteMultipleJoins(ASTPtr & query, const TablesWithColumns & tables, const String & database) { ASTSelectQuery & select = query->as(); Aliases aliases; if (ASTPtr with = select.with()) QueryAliasesNoSubqueriesVisitor(aliases).visit(with); QueryAliasesNoSubqueriesVisitor(aliases).visit(select.select()); CrossToInnerJoinVisitor::Data cross_to_inner{tables, aliases, database}; CrossToInnerJoinVisitor(cross_to_inner).visit(query); JoinToSubqueryTransformVisitor::Data join_to_subs_data{tables, aliases}; JoinToSubqueryTransformVisitor(join_to_subs_data).visit(query); } /// Checks that the current user has the SELECT privilege. static void checkAccessRightsForSelect( const Context & context, const StorageID & table_id, const StorageMetadataPtr & table_metadata, const Strings & required_columns, const TreeRewriterResult & syntax_analyzer_result) { if (!syntax_analyzer_result.has_explicit_columns && table_metadata && !table_metadata->getColumns().empty()) { /// For a trivial query like "SELECT count() FROM table" access is granted if at least /// one column is accessible. /// In this case just checking access for `required_columns` doesn't work correctly /// because `required_columns` will contain the name of a column of minimum size (see TreeRewriterResult::collectUsedColumns()) /// which is probably not the same column as the column the current user has access to. auto access = context.getAccess(); for (const auto & column : table_metadata->getColumns()) { if (access->isGranted(AccessType::SELECT, table_id.database_name, table_id.table_name, column.name)) return; } throw Exception(context.getUserName() + ": Not enough privileges. " "To execute this query it's necessary to have grant SELECT for at least one column on " + table_id.getFullTableName(), ErrorCodes::ACCESS_DENIED); } /// General check. context.checkAccess(AccessType::SELECT, table_id, required_columns); } /// Returns true if we should ignore quotas and limits for a specified table in the system database. static bool shouldIgnoreQuotaAndLimits(const StorageID & table_id) { if (table_id.database_name == DatabaseCatalog::SYSTEM_DATABASE) { static const boost::container::flat_set tables_ignoring_quota{"quotas", "quota_limits", "quota_usage", "quotas_usage", "one"}; if (tables_ignoring_quota.count(table_id.table_name)) return true; } return false; } InterpreterSelectQuery::InterpreterSelectQuery( const ASTPtr & query_ptr_, const Context & context_, const BlockInputStreamPtr & input_, std::optional input_pipe_, const StoragePtr & storage_, const SelectQueryOptions & options_, const Names & required_result_column_names, const StorageMetadataPtr & metadata_snapshot_) /// NOTE: the query almost always should be cloned because it will be modified during analysis. : IInterpreterUnionOrSelectQuery(options_.modify_inplace ? query_ptr_ : query_ptr_->clone(), context_, options_) , storage(storage_) , input(input_) , input_pipe(std::move(input_pipe_)) , log(&Poco::Logger::get("InterpreterSelectQuery")) , metadata_snapshot(metadata_snapshot_) { checkStackSize(); initSettings(); const Settings & settings = context->getSettingsRef(); if (settings.max_subquery_depth && options.subquery_depth > settings.max_subquery_depth) throw Exception("Too deep subqueries. Maximum: " + settings.max_subquery_depth.toString(), ErrorCodes::TOO_DEEP_SUBQUERIES); bool has_input = input || input_pipe; if (input) { /// Read from prepared input. source_header = input->getHeader(); } else if (input_pipe) { /// Read from prepared input. source_header = input_pipe->getHeader(); } // Only propagate WITH elements to subqueries if we're not a subquery if (options.subquery_depth == 0) { if (context->getSettingsRef().enable_global_with_statement) ApplyWithAliasVisitor().visit(query_ptr); ApplyWithSubqueryVisitor().visit(query_ptr); } JoinedTables joined_tables(getSubqueryContext(*context), getSelectQuery()); bool got_storage_from_query = false; if (!has_input && !storage) { storage = joined_tables.getLeftTableStorage(); got_storage_from_query = true; } if (storage) { table_lock = storage->lockForShare(context->getInitialQueryId(), context->getSettingsRef().lock_acquire_timeout); table_id = storage->getStorageID(); if (!metadata_snapshot) metadata_snapshot = storage->getInMemoryMetadataPtr(); } if (has_input || !joined_tables.resolveTables()) joined_tables.makeFakeTable(storage, metadata_snapshot, source_header); /// Rewrite JOINs if (!has_input && joined_tables.tablesCount() > 1) { rewriteMultipleJoins(query_ptr, joined_tables.tablesWithColumns(), context->getCurrentDatabase()); joined_tables.reset(getSelectQuery()); joined_tables.resolveTables(); if (storage && joined_tables.isLeftTableSubquery()) { /// Rewritten with subquery. Free storage locks here. storage = nullptr; table_lock.reset(); table_id = StorageID::createEmpty(); metadata_snapshot = nullptr; } } if (!has_input) { interpreter_subquery = joined_tables.makeLeftTableSubquery(options.subquery()); if (interpreter_subquery) source_header = interpreter_subquery->getSampleBlock(); } joined_tables.rewriteDistributedInAndJoins(query_ptr); max_streams = settings.max_threads; ASTSelectQuery & query = getSelectQuery(); std::shared_ptr table_join = joined_tables.makeTableJoin(query); ASTPtr row_policy_filter; if (storage) row_policy_filter = context->getRowPolicyCondition(table_id.getDatabaseName(), table_id.getTableName(), RowPolicy::SELECT_FILTER); StorageView * view = nullptr; if (storage) view = dynamic_cast(storage.get()); SubqueriesForSets subquery_for_sets; auto analyze = [&] (bool try_move_to_prewhere) { /// Allow push down and other optimizations for VIEW: replace with subquery and rewrite it. ASTPtr view_table; if (view) view->replaceWithSubquery(getSelectQuery(), view_table, metadata_snapshot); syntax_analyzer_result = TreeRewriter(*context).analyzeSelect( query_ptr, TreeRewriterResult(source_header.getNamesAndTypesList(), storage, metadata_snapshot), options, joined_tables.tablesWithColumns(), required_result_column_names, table_join); /// Save scalar sub queries's results in the query context if (!options.only_analyze && context->hasQueryContext()) for (const auto & it : syntax_analyzer_result->getScalars()) context->getQueryContext().addScalar(it.first, it.second); if (view) { /// Restore original view name. Save rewritten subquery for future usage in StorageView. query_info.view_query = view->restoreViewName(getSelectQuery(), view_table); view = nullptr; } if (try_move_to_prewhere && storage && !row_policy_filter && query.where() && !query.prewhere() && !query.final()) { /// PREWHERE optimization: transfer some condition from WHERE to PREWHERE if enabled and viable if (const auto * merge_tree = dynamic_cast(storage.get())) { SelectQueryInfo current_info; current_info.query = query_ptr; current_info.syntax_analyzer_result = syntax_analyzer_result; MergeTreeWhereOptimizer{current_info, *context, *merge_tree, metadata_snapshot, syntax_analyzer_result->requiredSourceColumns(), log}; } } query_analyzer = std::make_unique( query_ptr, syntax_analyzer_result, *context, metadata_snapshot, NameSet(required_result_column_names.begin(), required_result_column_names.end()), !options.only_analyze, options, std::move(subquery_for_sets)); if (!options.only_analyze) { if (query.sampleSize() && (input || input_pipe || !storage || !storage->supportsSampling())) throw Exception("Illegal SAMPLE: table doesn't support sampling", ErrorCodes::SAMPLING_NOT_SUPPORTED); if (query.final() && (input || input_pipe || !storage || !storage->supportsFinal())) throw Exception((!input && !input_pipe && storage) ? "Storage " + storage->getName() + " doesn't support FINAL" : "Illegal FINAL", ErrorCodes::ILLEGAL_FINAL); if (query.prewhere() && (input || input_pipe || !storage || !storage->supportsPrewhere())) throw Exception((!input && !input_pipe && storage) ? "Storage " + storage->getName() + " doesn't support PREWHERE" : "Illegal PREWHERE", ErrorCodes::ILLEGAL_PREWHERE); /// Save the new temporary tables in the query context for (const auto & it : query_analyzer->getExternalTables()) if (!context->tryResolveStorageID({"", it.first}, Context::ResolveExternal)) context->addExternalTable(it.first, std::move(*it.second)); } if (!options.only_analyze || options.modify_inplace) { if (syntax_analyzer_result->rewrite_subqueries) { /// remake interpreter_subquery when PredicateOptimizer rewrites subqueries and main table is subquery interpreter_subquery = joined_tables.makeLeftTableSubquery(options.subquery()); } } if (interpreter_subquery) { /// If there is an aggregation in the outer query, WITH TOTALS is ignored in the subquery. if (query_analyzer->hasAggregation()) interpreter_subquery->ignoreWithTotals(); } required_columns = syntax_analyzer_result->requiredSourceColumns(); if (storage) { source_header = metadata_snapshot->getSampleBlockForColumns(required_columns, storage->getVirtuals(), storage->getStorageID()); /// Fix source_header for filter actions. if (row_policy_filter) { filter_info = std::make_shared(); filter_info->column_name = generateFilterActions(filter_info->actions_dag, row_policy_filter, required_columns); source_header = metadata_snapshot->getSampleBlockForColumns( filter_info->actions_dag->getRequiredColumns().getNames(), storage->getVirtuals(), storage->getStorageID()); } } if (!options.only_analyze && storage && filter_info && query.prewhere()) throw Exception("PREWHERE is not supported if the table is filtered by row-level security expression", ErrorCodes::ILLEGAL_PREWHERE); /// Calculate structure of the result. result_header = getSampleBlockImpl(); }; analyze(settings.optimize_move_to_prewhere); bool need_analyze_again = false; if (analysis_result.prewhere_constant_filter_description.always_false || analysis_result.prewhere_constant_filter_description.always_true) { if (analysis_result.prewhere_constant_filter_description.always_true) query.setExpression(ASTSelectQuery::Expression::PREWHERE, {}); else query.setExpression(ASTSelectQuery::Expression::PREWHERE, std::make_shared(0u)); need_analyze_again = true; } if (analysis_result.where_constant_filter_description.always_false || analysis_result.where_constant_filter_description.always_true) { if (analysis_result.where_constant_filter_description.always_true) query.setExpression(ASTSelectQuery::Expression::WHERE, {}); else query.setExpression(ASTSelectQuery::Expression::WHERE, std::make_shared(0u)); need_analyze_again = true; } if (query.prewhere() && query.where()) { /// Filter block in WHERE instead to get better performance query.setExpression(ASTSelectQuery::Expression::WHERE, makeASTFunction("and", query.prewhere()->clone(), query.where()->clone())); need_analyze_again = true; } if (need_analyze_again) { subquery_for_sets = std::move(query_analyzer->getSubqueriesForSets()); /// Do not try move conditions to PREWHERE for the second time. /// Otherwise, we won't be able to fallback from inefficient PREWHERE to WHERE later. analyze(/* try_move_to_prewhere = */ false); } /// If there is no WHERE, filter blocks as usual if (query.prewhere() && !query.where()) analysis_result.prewhere_info->need_filter = true; if (table_id && got_storage_from_query && !joined_tables.isLeftTableFunction()) { /// The current user should have the SELECT privilege. /// If this table_id is for a table function we don't check access rights here because in this case they have been already checked in ITableFunction::execute(). checkAccessRightsForSelect(*context, table_id, metadata_snapshot, required_columns, *syntax_analyzer_result); /// Remove limits for some tables in the `system` database. if (shouldIgnoreQuotaAndLimits(table_id) && (joined_tables.tablesCount() <= 1)) { options.ignore_quota = true; options.ignore_limits = true; } } /// Blocks used in expression analysis contains size 1 const columns for constant folding and /// null non-const columns to avoid useless memory allocations. However, a valid block sample /// requires all columns to be of size 0, thus we need to sanitize the block here. sanitizeBlock(result_header, true); } void InterpreterSelectQuery::buildQueryPlan(QueryPlan & query_plan) { executeImpl(query_plan, input, std::move(input_pipe)); /// We must guarantee that result structure is the same as in getSampleBlock() if (!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(query_plan.getCurrentDataStream(), convert_actions_dag); query_plan.addStep(std::move(converting)); } } BlockIO InterpreterSelectQuery::execute() { BlockIO res; QueryPlan query_plan; buildQueryPlan(query_plan); res.pipeline = std::move(*query_plan.buildQueryPipeline()); return res; } Block InterpreterSelectQuery::getSampleBlockImpl() { OpenTelemetrySpanHolder span(__PRETTY_FUNCTION__); query_info.query = query_ptr; if (storage && !options.only_analyze) from_stage = storage->getQueryProcessingStage(*context, options.to_stage, query_info); /// Do I need to perform the first part of the pipeline - running on remote servers during distributed processing. bool first_stage = from_stage < QueryProcessingStage::WithMergeableState && options.to_stage >= QueryProcessingStage::WithMergeableState; /// Do I need to execute the second part of the pipeline - running on the initiating server during distributed processing. bool second_stage = from_stage <= QueryProcessingStage::WithMergeableState && options.to_stage > QueryProcessingStage::WithMergeableState; analysis_result = ExpressionAnalysisResult( *query_analyzer, metadata_snapshot, first_stage, second_stage, options.only_analyze, filter_info, source_header); if (options.to_stage == QueryProcessingStage::Enum::FetchColumns) { auto header = source_header; if (analysis_result.prewhere_info) { ExpressionActions(analysis_result.prewhere_info->prewhere_actions).execute(header); if (analysis_result.prewhere_info->remove_prewhere_column) header.erase(analysis_result.prewhere_info->prewhere_column_name); } return header; } if (options.to_stage == QueryProcessingStage::Enum::WithMergeableState) { if (!analysis_result.need_aggregate) { // What's the difference with selected_columns? return analysis_result.before_order_by->getResultColumns(); } Block header = analysis_result.before_aggregation->getResultColumns(); Block res; for (const auto & key : query_analyzer->aggregationKeys()) res.insert({nullptr, header.getByName(key.name).type, key.name}); for (const auto & aggregate : query_analyzer->aggregates()) { size_t arguments_size = aggregate.argument_names.size(); DataTypes argument_types(arguments_size); for (size_t j = 0; j < arguments_size; ++j) argument_types[j] = header.getByName(aggregate.argument_names[j]).type; DataTypePtr type = std::make_shared(aggregate.function, argument_types, aggregate.parameters); res.insert({nullptr, type, aggregate.column_name}); } return res; } if (options.to_stage == QueryProcessingStage::Enum::WithMergeableStateAfterAggregation) { // What's the difference with selected_columns? return analysis_result.before_order_by->getResultColumns(); } return analysis_result.final_projection->getResultColumns(); } static Field getWithFillFieldValue(const ASTPtr & node, const Context & context) { const auto & [field, type] = evaluateConstantExpression(node, context); if (!isColumnedAsNumber(type)) throw Exception("Illegal type " + type->getName() + " of WITH FILL expression, must be numeric type", ErrorCodes::INVALID_WITH_FILL_EXPRESSION); return field; } static FillColumnDescription getWithFillDescription(const ASTOrderByElement & order_by_elem, const Context & context) { FillColumnDescription descr; if (order_by_elem.fill_from) descr.fill_from = getWithFillFieldValue(order_by_elem.fill_from, context); if (order_by_elem.fill_to) descr.fill_to = getWithFillFieldValue(order_by_elem.fill_to, context); if (order_by_elem.fill_step) descr.fill_step = getWithFillFieldValue(order_by_elem.fill_step, context); else descr.fill_step = order_by_elem.direction; if (applyVisitor(FieldVisitorAccurateEquals(), descr.fill_step, Field{0})) throw Exception("WITH FILL STEP value cannot be zero", ErrorCodes::INVALID_WITH_FILL_EXPRESSION); if (order_by_elem.direction == 1) { if (applyVisitor(FieldVisitorAccurateLess(), descr.fill_step, Field{0})) throw Exception("WITH FILL STEP value cannot be negative for sorting in ascending direction", ErrorCodes::INVALID_WITH_FILL_EXPRESSION); if (!descr.fill_from.isNull() && !descr.fill_to.isNull() && applyVisitor(FieldVisitorAccurateLess(), descr.fill_to, descr.fill_from)) { throw Exception("WITH FILL TO value cannot be less than FROM value for sorting in ascending direction", ErrorCodes::INVALID_WITH_FILL_EXPRESSION); } } else { if (applyVisitor(FieldVisitorAccurateLess(), Field{0}, descr.fill_step)) throw Exception("WITH FILL STEP value cannot be positive for sorting in descending direction", ErrorCodes::INVALID_WITH_FILL_EXPRESSION); if (!descr.fill_from.isNull() && !descr.fill_to.isNull() && applyVisitor(FieldVisitorAccurateLess(), descr.fill_from, descr.fill_to)) { throw Exception("WITH FILL FROM value cannot be less than TO value for sorting in descending direction", ErrorCodes::INVALID_WITH_FILL_EXPRESSION); } } return descr; } static SortDescription getSortDescription(const ASTSelectQuery & query, const Context & context) { SortDescription order_descr; order_descr.reserve(query.orderBy()->children.size()); for (const auto & elem : query.orderBy()->children) { String name = elem->children.front()->getColumnName(); const auto & order_by_elem = elem->as(); std::shared_ptr collator; if (order_by_elem.collation) collator = std::make_shared(order_by_elem.collation->as().value.get()); if (order_by_elem.with_fill) { FillColumnDescription fill_desc = getWithFillDescription(order_by_elem, context); order_descr.emplace_back(name, order_by_elem.direction, order_by_elem.nulls_direction, collator, true, fill_desc); } else order_descr.emplace_back(name, order_by_elem.direction, order_by_elem.nulls_direction, collator); } return order_descr; } static SortDescription getSortDescriptionFromGroupBy(const ASTSelectQuery & query) { SortDescription order_descr; order_descr.reserve(query.groupBy()->children.size()); for (const auto & elem : query.groupBy()->children) { String name = elem->getColumnName(); order_descr.emplace_back(name, 1, 1); } return order_descr; } static UInt64 getLimitUIntValue(const ASTPtr & node, const Context & context, const std::string & expr) { const auto & [field, type] = evaluateConstantExpression(node, context); if (!isNativeNumber(type)) throw Exception("Illegal type " + type->getName() + " of " + expr + " expression, must be numeric type", ErrorCodes::INVALID_LIMIT_EXPRESSION); Field converted = convertFieldToType(field, DataTypeUInt64()); if (converted.isNull()) throw Exception("The value " + applyVisitor(FieldVisitorToString(), field) + " of " + expr + " expression is not representable as UInt64", ErrorCodes::INVALID_LIMIT_EXPRESSION); return converted.safeGet(); } static std::pair getLimitLengthAndOffset(const ASTSelectQuery & query, const Context & context) { UInt64 length = 0; UInt64 offset = 0; if (query.limitLength()) { length = getLimitUIntValue(query.limitLength(), context, "LIMIT"); if (query.limitOffset() && length) offset = getLimitUIntValue(query.limitOffset(), context, "OFFSET"); } else if (query.limitOffset()) offset = getLimitUIntValue(query.limitOffset(), context, "OFFSET"); return {length, offset}; } static UInt64 getLimitForSorting(const ASTSelectQuery & query, const Context & context) { /// Partial sort can be done if there is LIMIT but no DISTINCT or LIMIT BY, neither ARRAY JOIN. if (!query.distinct && !query.limitBy() && !query.limit_with_ties && !query.arrayJoinExpressionList() && query.limitLength()) { auto [limit_length, limit_offset] = getLimitLengthAndOffset(query, context); if (limit_length > std::numeric_limits::max() - limit_offset) return 0; return limit_length + limit_offset; } return 0; } static bool hasWithTotalsInAnySubqueryInFromClause(const ASTSelectQuery & query) { if (query.group_by_with_totals) return true; /** NOTE You can also check that the table in the subquery is distributed, and that it only looks at one shard. * In other cases, totals will be computed on the initiating server of the query, and it is not necessary to read the data to the end. */ if (auto query_table = extractTableExpression(query, 0)) { if (const auto * ast_union = query_table->as()) { for (const auto & elem : ast_union->list_of_selects->children) if (hasWithTotalsInAnySubqueryInFromClause(elem->as())) return true; } } return false; } void InterpreterSelectQuery::executeImpl(QueryPlan & query_plan, const BlockInputStreamPtr & prepared_input, std::optional prepared_pipe) { /** Streams of data. When the query is executed in parallel, we have several data streams. * If there is no GROUP BY, then perform all operations before ORDER BY and LIMIT in parallel, then * if there is an ORDER BY, then glue the streams using ResizeProcessor, and then MergeSorting transforms, * if not, then glue it using ResizeProcessor, * then apply LIMIT. * If there is GROUP BY, then we will perform all operations up to GROUP BY, inclusive, in parallel; * a parallel GROUP BY will glue streams into one, * then perform the remaining operations with one resulting stream. */ /// Now we will compose block streams that perform the necessary actions. auto & query = getSelectQuery(); const Settings & settings = context->getSettingsRef(); auto & expressions = analysis_result; auto & subqueries_for_sets = query_analyzer->getSubqueriesForSets(); bool intermediate_stage = false; bool to_aggregation_stage = false; bool from_aggregation_stage = false; if (options.only_analyze) { auto read_nothing = std::make_unique(source_header); query_plan.addStep(std::move(read_nothing)); if (expressions.prewhere_info) { auto prewhere_step = std::make_unique( query_plan.getCurrentDataStream(), expressions.prewhere_info->prewhere_actions, expressions.prewhere_info->prewhere_column_name, expressions.prewhere_info->remove_prewhere_column); prewhere_step->setStepDescription("PREWHERE"); query_plan.addStep(std::move(prewhere_step)); // To remove additional columns in dry run // For example, sample column which can be removed in this stage if (expressions.prewhere_info->remove_columns_actions) { auto remove_columns = std::make_unique( query_plan.getCurrentDataStream(), expressions.prewhere_info->remove_columns_actions); remove_columns->setStepDescription("Remove unnecessary columns after PREWHERE"); query_plan.addStep(std::move(remove_columns)); } } } else { if (prepared_input) { auto prepared_source_step = std::make_unique( Pipe(std::make_shared(prepared_input)), context); query_plan.addStep(std::move(prepared_source_step)); } else if (prepared_pipe) { auto prepared_source_step = std::make_unique(std::move(*prepared_pipe), context); query_plan.addStep(std::move(prepared_source_step)); } if (from_stage == QueryProcessingStage::WithMergeableState && options.to_stage == QueryProcessingStage::WithMergeableState) intermediate_stage = true; /// Support optimize_distributed_group_by_sharding_key /// Is running on the initiating server during distributed processing? if (from_stage == QueryProcessingStage::WithMergeableStateAfterAggregation) from_aggregation_stage = true; /// Is running on remote servers during distributed processing? if (options.to_stage == QueryProcessingStage::WithMergeableStateAfterAggregation) to_aggregation_stage = true; if (storage && expressions.filter_info && expressions.prewhere_info) throw Exception("PREWHERE is not supported if the table is filtered by row-level security expression", ErrorCodes::ILLEGAL_PREWHERE); /** Read the data from Storage. from_stage - to what stage the request was completed in Storage. */ executeFetchColumns(from_stage, query_plan, expressions.prewhere_info, expressions.columns_to_remove_after_prewhere); LOG_TRACE(log, "{} -> {}", QueryProcessingStage::toString(from_stage), QueryProcessingStage::toString(options.to_stage)); } if (options.to_stage > QueryProcessingStage::FetchColumns) { /// Do I need to aggregate in a separate row rows that have not passed max_rows_to_group_by. bool aggregate_overflow_row = expressions.need_aggregate && query.group_by_with_totals && settings.max_rows_to_group_by && settings.group_by_overflow_mode == OverflowMode::ANY && settings.totals_mode != TotalsMode::AFTER_HAVING_EXCLUSIVE; /// Do I need to immediately finalize the aggregate functions after the aggregation? bool aggregate_final = expressions.need_aggregate && options.to_stage > QueryProcessingStage::WithMergeableState && !query.group_by_with_totals && !query.group_by_with_rollup && !query.group_by_with_cube; auto preliminary_sort = [&]() { /** For distributed query processing, * if no GROUP, HAVING set, * but there is an ORDER or LIMIT, * then we will perform the preliminary sorting and LIMIT on the remote server. */ if (!expressions.second_stage && !expressions.need_aggregate && !expressions.hasHaving()) { if (expressions.has_order_by) executeOrder(query_plan, query_info.input_order_info); if (expressions.has_order_by && query.limitLength()) executeDistinct(query_plan, false, expressions.selected_columns, true); if (expressions.hasLimitBy()) { executeExpression(query_plan, expressions.before_limit_by, "Before LIMIT BY"); executeLimitBy(query_plan); } if (query.limitLength()) executePreLimit(query_plan, true); } }; if (intermediate_stage) { if (expressions.first_stage || expressions.second_stage) throw Exception("Query with intermediate stage cannot have any other stages", ErrorCodes::LOGICAL_ERROR); preliminary_sort(); if (expressions.need_aggregate) executeMergeAggregated(query_plan, aggregate_overflow_row, aggregate_final); } if (from_aggregation_stage) { if (intermediate_stage || expressions.first_stage || expressions.second_stage) throw Exception("Query with after aggregation stage cannot have any other stages", ErrorCodes::LOGICAL_ERROR); } if (expressions.first_stage) { if (expressions.hasFilter()) { auto row_level_security_step = std::make_unique( query_plan.getCurrentDataStream(), expressions.filter_info->actions_dag, expressions.filter_info->column_name, expressions.filter_info->do_remove_column); row_level_security_step->setStepDescription("Row-level security filter"); query_plan.addStep(std::move(row_level_security_step)); } if (expressions.before_array_join) { QueryPlanStepPtr before_array_join_step = std::make_unique( query_plan.getCurrentDataStream(), expressions.before_array_join); before_array_join_step->setStepDescription("Before ARRAY JOIN"); query_plan.addStep(std::move(before_array_join_step)); } if (expressions.array_join) { QueryPlanStepPtr array_join_step = std::make_unique( query_plan.getCurrentDataStream(), expressions.array_join); array_join_step->setStepDescription("ARRAY JOIN"); query_plan.addStep(std::move(array_join_step)); } if (expressions.before_join) { QueryPlanStepPtr before_join_step = std::make_unique( query_plan.getCurrentDataStream(), expressions.before_join); before_join_step->setStepDescription("Before JOIN"); query_plan.addStep(std::move(before_join_step)); } if (expressions.hasJoin()) { Block join_result_sample; JoinPtr join = expressions.join; join_result_sample = JoiningTransform::transformHeader( query_plan.getCurrentDataStream().header, expressions.join); QueryPlanStepPtr join_step = std::make_unique( query_plan.getCurrentDataStream(), expressions.join); join_step->setStepDescription("JOIN"); query_plan.addStep(std::move(join_step)); if (expressions.join_has_delayed_stream) { auto stream = std::make_shared(*join, join_result_sample, settings.max_block_size); auto source = std::make_shared(std::move(stream)); auto add_non_joined_rows_step = std::make_unique( query_plan.getCurrentDataStream(), std::move(source)); add_non_joined_rows_step->setStepDescription("Add non-joined rows after JOIN"); query_plan.addStep(std::move(add_non_joined_rows_step)); } } if (expressions.hasWhere()) executeWhere(query_plan, expressions.before_where, expressions.remove_where_filter); if (expressions.need_aggregate) { executeAggregation(query_plan, expressions.before_aggregation, aggregate_overflow_row, aggregate_final, query_info.input_order_info); /// We need to reset input order info, so that executeOrder can't use it query_info.input_order_info.reset(); } else { executeExpression(query_plan, expressions.before_window, "Before window functions"); executeWindow(query_plan); executeExpression(query_plan, expressions.before_order_by, "Before ORDER BY"); executeDistinct(query_plan, true, expressions.selected_columns, true); } preliminary_sort(); // If there is no global subqueries, we can run subqueries only when receive them on server. if (!query_analyzer->hasGlobalSubqueries() && !subqueries_for_sets.empty()) executeSubqueriesInSetsAndJoins(query_plan, subqueries_for_sets); } if (expressions.second_stage || from_aggregation_stage) { if (from_aggregation_stage) { /// No need to aggregate anything, since this was done on remote shards. } else if (expressions.need_aggregate) { /// If you need to combine aggregated results from multiple servers if (!expressions.first_stage) executeMergeAggregated(query_plan, aggregate_overflow_row, aggregate_final); if (!aggregate_final) { if (query.group_by_with_totals) { bool final = !query.group_by_with_rollup && !query.group_by_with_cube; executeTotalsAndHaving(query_plan, expressions.hasHaving(), expressions.before_having, aggregate_overflow_row, final); } if (query.group_by_with_rollup) executeRollupOrCube(query_plan, Modificator::ROLLUP); else if (query.group_by_with_cube) executeRollupOrCube(query_plan, Modificator::CUBE); if ((query.group_by_with_rollup || query.group_by_with_cube) && expressions.hasHaving()) { if (query.group_by_with_totals) throw Exception("WITH TOTALS and WITH ROLLUP or CUBE are not supported together in presence of HAVING", ErrorCodes::NOT_IMPLEMENTED); executeHaving(query_plan, expressions.before_having); } } else if (expressions.hasHaving()) executeHaving(query_plan, expressions.before_having); executeExpression(query_plan, expressions.before_window, "Before window functions"); executeWindow(query_plan); executeExpression(query_plan, expressions.before_order_by, "Before ORDER BY"); executeDistinct(query_plan, true, expressions.selected_columns, true); } else if (query.group_by_with_totals || query.group_by_with_rollup || query.group_by_with_cube) throw Exception("WITH TOTALS, ROLLUP or CUBE are not supported without aggregation", ErrorCodes::NOT_IMPLEMENTED); if (expressions.has_order_by) { /** If there is an ORDER BY for distributed query processing, * but there is no aggregation, then on the remote servers ORDER BY was made * - therefore, we merge the sorted streams from remote servers. */ if (!expressions.first_stage && !expressions.need_aggregate && !(query.group_by_with_totals && !aggregate_final)) executeMergeSorted(query_plan, "for ORDER BY"); else /// Otherwise, just sort. executeOrder(query_plan, query_info.input_order_info); } /** Optimization - if there are several sources and there is LIMIT, then first apply the preliminary LIMIT, * limiting the number of rows in each up to `offset + limit`. */ bool has_withfill = false; if (query.orderBy()) { SortDescription order_descr = getSortDescription(query, *context); for (auto & desc : order_descr) if (desc.with_fill) { has_withfill = true; break; } } bool has_prelimit = false; if (!to_aggregation_stage && query.limitLength() && !query.limit_with_ties && !hasWithTotalsInAnySubqueryInFromClause(query) && !query.arrayJoinExpressionList() && !query.distinct && !expressions.hasLimitBy() && !settings.extremes && !has_withfill) { executePreLimit(query_plan, false); has_prelimit = true; } /** If there was more than one stream, * then DISTINCT needs to be performed once again after merging all streams. */ if (query.distinct) executeDistinct(query_plan, false, expressions.selected_columns, false); if (expressions.hasLimitBy()) { executeExpression(query_plan, expressions.before_limit_by, "Before LIMIT BY"); executeLimitBy(query_plan); } executeWithFill(query_plan); /// If we have 'WITH TIES', we need execute limit before projection, /// because in that case columns from 'ORDER BY' are used. if (query.limit_with_ties) { executeLimit(query_plan); has_prelimit = true; } /// Projection not be done on the shards, since then initiator will not find column in blocks. /// (significant only for WithMergeableStateAfterAggregation). if (!to_aggregation_stage) { /// We must do projection after DISTINCT because projection may remove some columns. executeProjection(query_plan, expressions.final_projection); } /// Extremes are calculated before LIMIT, but after LIMIT BY. This is Ok. executeExtremes(query_plan); /// Limit is no longer needed if there is prelimit. if (!to_aggregation_stage && !has_prelimit) executeLimit(query_plan); if (!to_aggregation_stage) executeOffset(query_plan); } } if (!subqueries_for_sets.empty() && (expressions.hasHaving() || query_analyzer->hasGlobalSubqueries())) executeSubqueriesInSetsAndJoins(query_plan, subqueries_for_sets); } static StreamLocalLimits getLimitsForStorage(const Settings & settings, const SelectQueryOptions & options) { StreamLocalLimits limits; limits.mode = LimitsMode::LIMITS_TOTAL; limits.size_limits = SizeLimits(settings.max_rows_to_read, settings.max_bytes_to_read, settings.read_overflow_mode); limits.speed_limits.max_execution_time = settings.max_execution_time; limits.timeout_overflow_mode = settings.timeout_overflow_mode; /** Quota and minimal speed restrictions are checked on the initiating server of the request, and not on remote servers, * because the initiating server has a summary of the execution of the request on all servers. * * But limits on data size to read and maximum execution time are reasonable to check both on initiator and * additionally on each remote server, because these limits are checked per block of data processed, * and remote servers may process way more blocks of data than are received by initiator. * * The limits to throttle maximum execution speed is also checked on all servers. */ if (options.to_stage == QueryProcessingStage::Complete) { limits.speed_limits.min_execution_rps = settings.min_execution_speed; limits.speed_limits.min_execution_bps = settings.min_execution_speed_bytes; } limits.speed_limits.max_execution_rps = settings.max_execution_speed; limits.speed_limits.max_execution_bps = settings.max_execution_speed_bytes; limits.speed_limits.timeout_before_checking_execution_speed = settings.timeout_before_checking_execution_speed; return limits; } void InterpreterSelectQuery::addEmptySourceToQueryPlan(QueryPlan & query_plan, const Block & source_header, const SelectQueryInfo & query_info) { Pipe pipe(std::make_shared(source_header)); if (query_info.prewhere_info) { if (query_info.prewhere_info->alias_actions) { pipe.addSimpleTransform([&](const Block & header) { return std::make_shared(header, query_info.prewhere_info->alias_actions); }); } pipe.addSimpleTransform([&](const Block & header) { return std::make_shared( header, query_info.prewhere_info->prewhere_actions, query_info.prewhere_info->prewhere_column_name, query_info.prewhere_info->remove_prewhere_column); }); // To remove additional columns // In some cases, we did not read any marks so that the pipeline.streams is empty // Thus, some columns in prewhere are not removed as expected // This leads to mismatched header in distributed table if (query_info.prewhere_info->remove_columns_actions) { pipe.addSimpleTransform([&](const Block & header) { return std::make_shared( header, query_info.prewhere_info->remove_columns_actions); }); } } auto read_from_pipe = std::make_unique(std::move(pipe)); read_from_pipe->setStepDescription("Read from NullSource"); query_plan.addStep(std::move(read_from_pipe)); } void InterpreterSelectQuery::executeFetchColumns( QueryProcessingStage::Enum processing_stage, QueryPlan & query_plan, const PrewhereDAGInfoPtr & prewhere_info, const NameSet & columns_to_remove_after_prewhere) { auto & query = getSelectQuery(); const Settings & settings = context->getSettingsRef(); /// Optimization for trivial query like SELECT count() FROM table. bool optimize_trivial_count = syntax_analyzer_result->optimize_trivial_count && (settings.max_parallel_replicas <= 1) && storage && storage->getName() != "MaterializeMySQL" && !filter_info && processing_stage == QueryProcessingStage::FetchColumns && query_analyzer->hasAggregation() && (query_analyzer->aggregates().size() == 1) && typeid_cast(query_analyzer->aggregates()[0].function.get()); if (optimize_trivial_count) { const auto & desc = query_analyzer->aggregates()[0]; const auto & func = desc.function; std::optional num_rows{}; if (!query.prewhere() && !query.where()) num_rows = storage->totalRows(settings); else // It's possible to optimize count() given only partition predicates { SelectQueryInfo temp_query_info; temp_query_info.query = query_ptr; temp_query_info.syntax_analyzer_result = syntax_analyzer_result; temp_query_info.sets = query_analyzer->getPreparedSets(); num_rows = storage->totalRowsByPartitionPredicate(temp_query_info, *context); } if (num_rows) { AggregateFunctionCount & agg_count = static_cast(*func); /// We will process it up to "WithMergeableState". std::vector state(agg_count.sizeOfData()); AggregateDataPtr place = state.data(); agg_count.create(place); SCOPE_EXIT(agg_count.destroy(place)); agg_count.set(place, *num_rows); auto column = ColumnAggregateFunction::create(func); column->insertFrom(place); Block header = analysis_result.before_aggregation->getResultColumns(); size_t arguments_size = desc.argument_names.size(); DataTypes argument_types(arguments_size); for (size_t j = 0; j < arguments_size; ++j) argument_types[j] = header.getByName(desc.argument_names[j]).type; Block block_with_count{ {std::move(column), std::make_shared(func, argument_types, desc.parameters), desc.column_name}}; auto istream = std::make_shared(block_with_count); auto prepared_count = std::make_unique(Pipe(std::make_shared(istream)), context); prepared_count->setStepDescription("Optimized trivial count"); query_plan.addStep(std::move(prepared_count)); from_stage = QueryProcessingStage::WithMergeableState; analysis_result.first_stage = false; return; } } /// Actions to calculate ALIAS if required. ActionsDAGPtr alias_actions; if (storage) { /// Append columns from the table filter to required auto row_policy_filter = context->getRowPolicyCondition(table_id.getDatabaseName(), table_id.getTableName(), RowPolicy::SELECT_FILTER); if (row_policy_filter) { auto initial_required_columns = required_columns; ActionsDAGPtr actions_dag; generateFilterActions(actions_dag, row_policy_filter, initial_required_columns); auto required_columns_from_filter = actions_dag->getRequiredColumns(); for (const auto & column : required_columns_from_filter) { if (required_columns.end() == std::find(required_columns.begin(), required_columns.end(), column.name)) required_columns.push_back(column.name); } } /// Detect, if ALIAS columns are required for query execution auto alias_columns_required = false; const ColumnsDescription & storage_columns = metadata_snapshot->getColumns(); for (const auto & column_name : required_columns) { auto column_default = storage_columns.getDefault(column_name); if (column_default && column_default->kind == ColumnDefaultKind::Alias) { alias_columns_required = true; break; } } /// There are multiple sources of required columns: /// - raw required columns, /// - columns deduced from ALIAS columns, /// - raw required columns from PREWHERE, /// - columns deduced from ALIAS columns from PREWHERE. /// PREWHERE is a special case, since we need to resolve it and pass directly to `IStorage::read()` /// before any other executions. if (alias_columns_required) { NameSet required_columns_from_prewhere; /// Set of all (including ALIAS) required columns for PREWHERE NameSet required_aliases_from_prewhere; /// Set of ALIAS required columns for PREWHERE if (prewhere_info) { /// Get some columns directly from PREWHERE expression actions auto prewhere_required_columns = prewhere_info->prewhere_actions->getRequiredColumns().getNames(); required_columns_from_prewhere.insert(prewhere_required_columns.begin(), prewhere_required_columns.end()); } /// Expression, that contains all raw required columns ASTPtr required_columns_all_expr = std::make_shared(); /// Expression, that contains raw required columns for PREWHERE ASTPtr required_columns_from_prewhere_expr = std::make_shared(); /// Sort out already known required columns between expressions, /// also populate `required_aliases_from_prewhere`. for (const auto & column : required_columns) { ASTPtr column_expr; const auto column_default = storage_columns.getDefault(column); bool is_alias = column_default && column_default->kind == ColumnDefaultKind::Alias; if (is_alias) { auto column_decl = storage_columns.get(column); column_expr = column_default->expression->clone(); // recursive visit for alias to alias replaceAliasColumnsInQuery(column_expr, metadata_snapshot->getColumns(), syntax_analyzer_result->getArrayJoinSourceNameSet(), *context); column_expr = addTypeConversionToAST(std::move(column_expr), column_decl.type->getName(), metadata_snapshot->getColumns().getAll(), *context); column_expr = setAlias(column_expr, column); } else column_expr = std::make_shared(column); if (required_columns_from_prewhere.count(column)) { required_columns_from_prewhere_expr->children.emplace_back(std::move(column_expr)); if (is_alias) required_aliases_from_prewhere.insert(column); } else required_columns_all_expr->children.emplace_back(std::move(column_expr)); } /// Columns, which we will get after prewhere and filter executions. NamesAndTypesList required_columns_after_prewhere; NameSet required_columns_after_prewhere_set; /// Collect required columns from prewhere expression actions. if (prewhere_info) { NameSet columns_to_remove(columns_to_remove_after_prewhere.begin(), columns_to_remove_after_prewhere.end()); Block prewhere_actions_result = prewhere_info->prewhere_actions->getResultColumns(); /// Populate required columns with the columns, added by PREWHERE actions and not removed afterwards. /// XXX: looks hacky that we already know which columns after PREWHERE we won't need for sure. for (const auto & column : prewhere_actions_result) { if (prewhere_info->remove_prewhere_column && column.name == prewhere_info->prewhere_column_name) continue; if (columns_to_remove.count(column.name)) continue; required_columns_all_expr->children.emplace_back(std::make_shared(column.name)); required_columns_after_prewhere.emplace_back(column.name, column.type); } required_columns_after_prewhere_set = ext::map(required_columns_after_prewhere, [](const auto & it) { return it.name; }); } auto syntax_result = TreeRewriter(*context).analyze(required_columns_all_expr, required_columns_after_prewhere, storage, metadata_snapshot); alias_actions = ExpressionAnalyzer(required_columns_all_expr, syntax_result, *context).getActionsDAG(true); /// The set of required columns could be added as a result of adding an action to calculate ALIAS. required_columns = alias_actions->getRequiredColumns().getNames(); /// Do not remove prewhere filter if it is a column which is used as alias. if (prewhere_info && prewhere_info->remove_prewhere_column) if (required_columns.end() != std::find(required_columns.begin(), required_columns.end(), prewhere_info->prewhere_column_name)) prewhere_info->remove_prewhere_column = false; /// Remove columns which will be added by prewhere. required_columns.erase(std::remove_if(required_columns.begin(), required_columns.end(), [&](const String & name) { return required_columns_after_prewhere_set.count(name) != 0; }), required_columns.end()); if (prewhere_info) { /// Don't remove columns which are needed to be aliased. for (const auto & name : required_columns) prewhere_info->prewhere_actions->tryRestoreColumn(name); auto analyzed_result = TreeRewriter(*context).analyze(required_columns_from_prewhere_expr, metadata_snapshot->getColumns().getAllPhysical()); prewhere_info->alias_actions = ExpressionAnalyzer(required_columns_from_prewhere_expr, analyzed_result, *context).getActionsDAG(true, false); /// Add (physical?) columns required by alias actions. auto required_columns_from_alias = prewhere_info->alias_actions->getRequiredColumns(); Block prewhere_actions_result = prewhere_info->prewhere_actions->getResultColumns(); for (auto & column : required_columns_from_alias) if (!prewhere_actions_result.has(column.name)) if (required_columns.end() == std::find(required_columns.begin(), required_columns.end(), column.name)) required_columns.push_back(column.name); /// Add physical columns required by prewhere actions. for (const auto & column : required_columns_from_prewhere) if (required_aliases_from_prewhere.count(column) == 0) if (required_columns.end() == std::find(required_columns.begin(), required_columns.end(), column)) required_columns.push_back(column); } } } /// Limitation on the number of columns to read. /// It's not applied in 'only_analyze' mode, because the query could be analyzed without removal of unnecessary columns. if (!options.only_analyze && settings.max_columns_to_read && required_columns.size() > settings.max_columns_to_read) throw Exception("Limit for number of columns to read exceeded. " "Requested: " + toString(required_columns.size()) + ", maximum: " + settings.max_columns_to_read.toString(), ErrorCodes::TOO_MANY_COLUMNS); /// General limit for the number of threads. size_t max_threads_execute_query = settings.max_threads; /** With distributed query processing, almost no computations are done in the threads, * but wait and receive data from remote servers. * If we have 20 remote servers, and max_threads = 8, then it would not be very good * connect and ask only 8 servers at a time. * To simultaneously query more remote servers, * instead of max_threads, max_distributed_connections is used. */ bool is_remote = false; if (storage && storage->isRemote()) { is_remote = true; max_threads_execute_query = max_streams = settings.max_distributed_connections; } UInt64 max_block_size = settings.max_block_size; auto [limit_length, limit_offset] = getLimitLengthAndOffset(query, *context); /** Optimization - if not specified DISTINCT, WHERE, GROUP, HAVING, ORDER, LIMIT BY, WITH TIES but LIMIT is specified, and limit + offset < max_block_size, * then as the block size we will use limit + offset (not to read more from the table than requested), * and also set the number of threads to 1. */ if (!query.distinct && !query.limit_with_ties && !query.prewhere() && !query.where() && !query.groupBy() && !query.having() && !query.orderBy() && !query.limitBy() && query.limitLength() && !query_analyzer->hasAggregation() && limit_length <= std::numeric_limits::max() - limit_offset && limit_length + limit_offset < max_block_size) { max_block_size = std::max(UInt64(1), limit_length + limit_offset); max_threads_execute_query = max_streams = 1; } if (!max_block_size) throw Exception("Setting 'max_block_size' cannot be zero", ErrorCodes::PARAMETER_OUT_OF_BOUND); /// Initialize the initial data streams to which the query transforms are superimposed. Table or subquery or prepared input? if (query_plan.isInitialized()) { /// Prepared input. } else if (interpreter_subquery) { /// Subquery. /// If we need less number of columns that subquery have - update the interpreter. if (required_columns.size() < source_header.columns()) { ASTPtr subquery = extractTableExpression(query, 0); if (!subquery) throw Exception("Subquery expected", ErrorCodes::LOGICAL_ERROR); interpreter_subquery = std::make_unique( subquery, getSubqueryContext(*context), options.copy().subquery().noModify(), required_columns); if (query_analyzer->hasAggregation()) interpreter_subquery->ignoreWithTotals(); } interpreter_subquery->buildQueryPlan(query_plan); query_plan.addInterpreterContext(context); } else if (storage) { /// Table. if (max_streams == 0) throw Exception("Logical error: zero number of streams requested", ErrorCodes::LOGICAL_ERROR); /// If necessary, we request more sources than the number of threads - to distribute the work evenly over the threads. if (max_streams > 1 && !is_remote) max_streams *= settings.max_streams_to_max_threads_ratio; query_info.syntax_analyzer_result = syntax_analyzer_result; query_info.sets = query_analyzer->getPreparedSets(); if (prewhere_info) { query_info.prewhere_info = std::make_shared( std::make_shared(prewhere_info->prewhere_actions), prewhere_info->prewhere_column_name); if (prewhere_info->alias_actions) query_info.prewhere_info->alias_actions = std::make_shared(prewhere_info->alias_actions); if (prewhere_info->remove_columns_actions) query_info.prewhere_info->remove_columns_actions = std::make_shared(prewhere_info->remove_columns_actions); query_info.prewhere_info->remove_prewhere_column = prewhere_info->remove_prewhere_column; query_info.prewhere_info->need_filter = prewhere_info->need_filter; } /// Create optimizer with prepared actions. /// Maybe we will need to calc input_order_info later, e.g. while reading from StorageMerge. if (analysis_result.optimize_read_in_order || analysis_result.optimize_aggregation_in_order) { if (analysis_result.optimize_read_in_order) query_info.order_optimizer = std::make_shared( analysis_result.order_by_elements_actions, getSortDescription(query, *context), query_info.syntax_analyzer_result); else query_info.order_optimizer = std::make_shared( analysis_result.group_by_elements_actions, getSortDescriptionFromGroupBy(query), query_info.syntax_analyzer_result); query_info.input_order_info = query_info.order_optimizer->getInputOrder(metadata_snapshot, *context); } StreamLocalLimits limits; SizeLimits leaf_limits; std::shared_ptr quota; /// Set the limits and quota for reading data, the speed and time of the query. if (!options.ignore_limits) { limits = getLimitsForStorage(settings, options); leaf_limits = SizeLimits(settings.max_rows_to_read_leaf, settings.max_bytes_to_read_leaf, settings.read_overflow_mode_leaf); } if (!options.ignore_quota && (options.to_stage == QueryProcessingStage::Complete)) quota = context->getQuota(); storage->read(query_plan, required_columns, metadata_snapshot, query_info, *context, processing_stage, max_block_size, max_streams); if (context->hasQueryContext() && !options.is_internal) { auto local_storage_id = storage->getStorageID(); context->getQueryContext().addQueryAccessInfo( backQuoteIfNeed(local_storage_id.getDatabaseName()), local_storage_id.getFullTableName(), required_columns); } /// Create step which reads from empty source if storage has no data. if (!query_plan.isInitialized()) { auto header = metadata_snapshot->getSampleBlockForColumns( required_columns, storage->getVirtuals(), storage->getStorageID()); addEmptySourceToQueryPlan(query_plan, header, query_info); } /// Extend lifetime of context, table lock, storage. Set limits and quota. auto adding_limits_and_quota = std::make_unique( query_plan.getCurrentDataStream(), storage, std::move(table_lock), limits, leaf_limits, std::move(quota), context); adding_limits_and_quota->setStepDescription("Set limits and quota after reading from storage"); query_plan.addStep(std::move(adding_limits_and_quota)); } else throw Exception("Logical error in InterpreterSelectQuery: nowhere to read", ErrorCodes::LOGICAL_ERROR); /// Specify the number of threads only if it wasn't specified in storage. /// /// But in case of remote query and prefer_localhost_replica=1 (default) /// The inner local query (that is done in the same process, without /// network interaction), it will setMaxThreads earlier and distributed /// query will not update it. if (!query_plan.getMaxThreads() || is_remote) query_plan.setMaxThreads(max_threads_execute_query); /// Aliases in table declaration. if (processing_stage == QueryProcessingStage::FetchColumns && alias_actions) { auto table_aliases = std::make_unique(query_plan.getCurrentDataStream(), alias_actions); table_aliases->setStepDescription("Add table aliases"); query_plan.addStep(std::move(table_aliases)); } } void InterpreterSelectQuery::executeWhere(QueryPlan & query_plan, const ActionsDAGPtr & expression, bool remove_filter) { auto where_step = std::make_unique( query_plan.getCurrentDataStream(), expression, getSelectQuery().where()->getColumnName(), remove_filter); where_step->setStepDescription("WHERE"); query_plan.addStep(std::move(where_step)); } void InterpreterSelectQuery::executeAggregation(QueryPlan & query_plan, const ActionsDAGPtr & expression, bool overflow_row, bool final, InputOrderInfoPtr group_by_info) { auto expression_before_aggregation = std::make_unique(query_plan.getCurrentDataStream(), expression); expression_before_aggregation->setStepDescription("Before GROUP BY"); query_plan.addStep(std::move(expression_before_aggregation)); const auto & header_before_aggregation = query_plan.getCurrentDataStream().header; ColumnNumbers keys; for (const auto & key : query_analyzer->aggregationKeys()) keys.push_back(header_before_aggregation.getPositionByName(key.name)); AggregateDescriptions aggregates = query_analyzer->aggregates(); for (auto & descr : aggregates) if (descr.arguments.empty()) for (const auto & name : descr.argument_names) descr.arguments.push_back(header_before_aggregation.getPositionByName(name)); const Settings & settings = context->getSettingsRef(); Aggregator::Params params(header_before_aggregation, keys, aggregates, overflow_row, settings.max_rows_to_group_by, settings.group_by_overflow_mode, settings.group_by_two_level_threshold, settings.group_by_two_level_threshold_bytes, settings.max_bytes_before_external_group_by, settings.empty_result_for_aggregation_by_empty_set, context->getTemporaryVolume(), settings.max_threads, settings.min_free_disk_space_for_temporary_data); SortDescription group_by_sort_description; if (group_by_info && settings.optimize_aggregation_in_order) group_by_sort_description = getSortDescriptionFromGroupBy(getSelectQuery()); else group_by_info = nullptr; auto merge_threads = max_streams; auto temporary_data_merge_threads = settings.aggregation_memory_efficient_merge_threads ? static_cast(settings.aggregation_memory_efficient_merge_threads) : static_cast(settings.max_threads); bool storage_has_evenly_distributed_read = storage && storage->hasEvenlyDistributedRead(); auto aggregating_step = std::make_unique( query_plan.getCurrentDataStream(), params, final, settings.max_block_size, merge_threads, temporary_data_merge_threads, storage_has_evenly_distributed_read, std::move(group_by_info), std::move(group_by_sort_description)); query_plan.addStep(std::move(aggregating_step)); } void InterpreterSelectQuery::executeMergeAggregated(QueryPlan & query_plan, bool overflow_row, bool final) { const auto & header_before_merge = query_plan.getCurrentDataStream().header; ColumnNumbers keys; for (const auto & key : query_analyzer->aggregationKeys()) keys.push_back(header_before_merge.getPositionByName(key.name)); /** There are two modes of distributed aggregation. * * 1. In different threads read from the remote servers blocks. * Save all the blocks in the RAM. Merge blocks. * If the aggregation is two-level - parallelize to the number of buckets. * * 2. In one thread, read blocks from different servers in order. * RAM stores only one block from each server. * If the aggregation is a two-level aggregation, we consistently merge the blocks of each next level. * * The second option consumes less memory (up to 256 times less) * in the case of two-level aggregation, which is used for large results after GROUP BY, * but it can work more slowly. */ const Settings & settings = context->getSettingsRef(); Aggregator::Params params(header_before_merge, keys, query_analyzer->aggregates(), overflow_row, settings.max_threads); auto transform_params = std::make_shared(params, final); auto merging_aggregated = std::make_unique( query_plan.getCurrentDataStream(), std::move(transform_params), settings.distributed_aggregation_memory_efficient, settings.max_threads, settings.aggregation_memory_efficient_merge_threads); query_plan.addStep(std::move(merging_aggregated)); } void InterpreterSelectQuery::executeHaving(QueryPlan & query_plan, const ActionsDAGPtr & expression) { auto having_step = std::make_unique( query_plan.getCurrentDataStream(), expression, getSelectQuery().having()->getColumnName(), false); having_step->setStepDescription("HAVING"); query_plan.addStep(std::move(having_step)); } void InterpreterSelectQuery::executeTotalsAndHaving(QueryPlan & query_plan, bool has_having, const ActionsDAGPtr & expression, bool overflow_row, bool final) { const Settings & settings = context->getSettingsRef(); auto totals_having_step = std::make_unique( query_plan.getCurrentDataStream(), overflow_row, expression, has_having ? getSelectQuery().having()->getColumnName() : "", settings.totals_mode, settings.totals_auto_threshold, final); query_plan.addStep(std::move(totals_having_step)); } void InterpreterSelectQuery::executeRollupOrCube(QueryPlan & query_plan, Modificator modificator) { const auto & header_before_transform = query_plan.getCurrentDataStream().header; ColumnNumbers keys; for (const auto & key : query_analyzer->aggregationKeys()) keys.push_back(header_before_transform.getPositionByName(key.name)); const Settings & settings = context->getSettingsRef(); Aggregator::Params params(header_before_transform, keys, query_analyzer->aggregates(), false, settings.max_rows_to_group_by, settings.group_by_overflow_mode, 0, 0, settings.max_bytes_before_external_group_by, settings.empty_result_for_aggregation_by_empty_set, context->getTemporaryVolume(), settings.max_threads, settings.min_free_disk_space_for_temporary_data); auto transform_params = std::make_shared(params, true); QueryPlanStepPtr step; if (modificator == Modificator::ROLLUP) step = std::make_unique(query_plan.getCurrentDataStream(), std::move(transform_params)); else step = std::make_unique(query_plan.getCurrentDataStream(), std::move(transform_params)); query_plan.addStep(std::move(step)); } void InterpreterSelectQuery::executeExpression(QueryPlan & query_plan, const ActionsDAGPtr & expression, const std::string & description) { if (!expression) { return; } auto expression_step = std::make_unique(query_plan.getCurrentDataStream(), expression); expression_step->setStepDescription(description); query_plan.addStep(std::move(expression_step)); } void InterpreterSelectQuery::executeWindow(QueryPlan & query_plan) { for (const auto & [_, w] : query_analyzer->windowDescriptions()) { const Settings & settings = context->getSettingsRef(); auto partial_sorting = std::make_unique( query_plan.getCurrentDataStream(), w.full_sort_description, 0 /* LIMIT */, SizeLimits(settings.max_rows_to_sort, settings.max_bytes_to_sort, settings.sort_overflow_mode)); partial_sorting->setStepDescription("Sort each block for window '" + w.window_name + "'"); query_plan.addStep(std::move(partial_sorting)); auto merge_sorting_step = std::make_unique( query_plan.getCurrentDataStream(), w.full_sort_description, settings.max_block_size, 0 /* LIMIT */, settings.max_bytes_before_remerge_sort, settings.remerge_sort_lowered_memory_bytes_ratio, settings.max_bytes_before_external_sort, context->getTemporaryVolume(), settings.min_free_disk_space_for_temporary_data); merge_sorting_step->setStepDescription("Merge sorted blocks for window '" + w.window_name + "'"); query_plan.addStep(std::move(merge_sorting_step)); // First MergeSorted, now MergingSorted. auto merging_sorted = std::make_unique( query_plan.getCurrentDataStream(), w.full_sort_description, settings.max_block_size, 0 /* LIMIT */); merging_sorted->setStepDescription("Merge sorted streams for window '" + w.window_name + "'"); query_plan.addStep(std::move(merging_sorted)); auto window_step = std::make_unique( query_plan.getCurrentDataStream(), w, w.window_functions); window_step->setStepDescription("Window step for window '" + w.window_name + "'"); query_plan.addStep(std::move(window_step)); } } void InterpreterSelectQuery::executeOrderOptimized(QueryPlan & query_plan, InputOrderInfoPtr input_sorting_info, UInt64 limit, SortDescription & output_order_descr) { const Settings & settings = context->getSettingsRef(); auto finish_sorting_step = std::make_unique( query_plan.getCurrentDataStream(), input_sorting_info->order_key_prefix_descr, output_order_descr, settings.max_block_size, limit); query_plan.addStep(std::move(finish_sorting_step)); } void InterpreterSelectQuery::executeOrder(QueryPlan & query_plan, InputOrderInfoPtr input_sorting_info) { auto & query = getSelectQuery(); SortDescription output_order_descr = getSortDescription(query, *context); UInt64 limit = getLimitForSorting(query, *context); if (input_sorting_info) { /* Case of sorting with optimization using sorting key. * We have several threads, each of them reads batch of parts in direct * or reverse order of sorting key using one input stream per part * and then merge them into one sorted stream. * At this stage we merge per-thread streams into one. */ executeOrderOptimized(query_plan, input_sorting_info, limit, output_order_descr); return; } const Settings & settings = context->getSettingsRef(); auto partial_sorting = std::make_unique( query_plan.getCurrentDataStream(), output_order_descr, limit, SizeLimits(settings.max_rows_to_sort, settings.max_bytes_to_sort, settings.sort_overflow_mode)); partial_sorting->setStepDescription("Sort each block for ORDER BY"); query_plan.addStep(std::move(partial_sorting)); /// Merge the sorted blocks. auto merge_sorting_step = std::make_unique( query_plan.getCurrentDataStream(), output_order_descr, settings.max_block_size, limit, settings.max_bytes_before_remerge_sort, settings.remerge_sort_lowered_memory_bytes_ratio, settings.max_bytes_before_external_sort, context->getTemporaryVolume(), settings.min_free_disk_space_for_temporary_data); merge_sorting_step->setStepDescription("Merge sorted blocks for ORDER BY"); query_plan.addStep(std::move(merge_sorting_step)); /// If there are several streams, we merge them into one executeMergeSorted(query_plan, output_order_descr, limit, "for ORDER BY"); } void InterpreterSelectQuery::executeMergeSorted(QueryPlan & query_plan, const std::string & description) { auto & query = getSelectQuery(); SortDescription order_descr = getSortDescription(query, *context); UInt64 limit = getLimitForSorting(query, *context); executeMergeSorted(query_plan, order_descr, limit, description); } void InterpreterSelectQuery::executeMergeSorted(QueryPlan & query_plan, const SortDescription & sort_description, UInt64 limit, const std::string & description) { const Settings & settings = context->getSettingsRef(); auto merging_sorted = std::make_unique( query_plan.getCurrentDataStream(), sort_description, settings.max_block_size, limit); merging_sorted->setStepDescription("Merge sorted streams " + description); query_plan.addStep(std::move(merging_sorted)); } void InterpreterSelectQuery::executeProjection(QueryPlan & query_plan, const ActionsDAGPtr & expression) { auto projection_step = std::make_unique(query_plan.getCurrentDataStream(), expression); projection_step->setStepDescription("Projection"); query_plan.addStep(std::move(projection_step)); } void InterpreterSelectQuery::executeDistinct(QueryPlan & query_plan, bool before_order, Names columns, bool pre_distinct) { auto & query = getSelectQuery(); if (query.distinct) { const Settings & settings = context->getSettingsRef(); auto [limit_length, limit_offset] = getLimitLengthAndOffset(query, *context); UInt64 limit_for_distinct = 0; /// If after this stage of DISTINCT ORDER BY is not executed, /// then you can get no more than limit_length + limit_offset of different rows. if ((!query.orderBy() || !before_order) && limit_length <= std::numeric_limits::max() - limit_offset) limit_for_distinct = limit_length + limit_offset; SizeLimits limits(settings.max_rows_in_distinct, settings.max_bytes_in_distinct, settings.distinct_overflow_mode); auto distinct_step = std::make_unique( query_plan.getCurrentDataStream(), limits, limit_for_distinct, columns, pre_distinct); if (pre_distinct) distinct_step->setStepDescription("Preliminary DISTINCT"); query_plan.addStep(std::move(distinct_step)); } } /// Preliminary LIMIT - is used in every source, if there are several sources, before they are combined. void InterpreterSelectQuery::executePreLimit(QueryPlan & query_plan, bool do_not_skip_offset) { auto & query = getSelectQuery(); /// If there is LIMIT if (query.limitLength()) { auto [limit_length, limit_offset] = getLimitLengthAndOffset(query, *context); if (do_not_skip_offset) { if (limit_length > std::numeric_limits::max() - limit_offset) return; limit_length += limit_offset; limit_offset = 0; } auto limit = std::make_unique(query_plan.getCurrentDataStream(), limit_length, limit_offset); limit->setStepDescription("preliminary LIMIT"); query_plan.addStep(std::move(limit)); } } void InterpreterSelectQuery::executeLimitBy(QueryPlan & query_plan) { auto & query = getSelectQuery(); if (!query.limitByLength() || !query.limitBy()) return; Names columns; for (const auto & elem : query.limitBy()->children) columns.emplace_back(elem->getColumnName()); UInt64 length = getLimitUIntValue(query.limitByLength(), *context, "LIMIT"); UInt64 offset = (query.limitByOffset() ? getLimitUIntValue(query.limitByOffset(), *context, "OFFSET") : 0); auto limit_by = std::make_unique(query_plan.getCurrentDataStream(), length, offset, columns); query_plan.addStep(std::move(limit_by)); } void InterpreterSelectQuery::executeWithFill(QueryPlan & query_plan) { auto & query = getSelectQuery(); if (query.orderBy()) { SortDescription order_descr = getSortDescription(query, *context); SortDescription fill_descr; for (auto & desc : order_descr) { if (desc.with_fill) fill_descr.push_back(desc); } if (fill_descr.empty()) return; auto filling_step = std::make_unique(query_plan.getCurrentDataStream(), std::move(fill_descr)); query_plan.addStep(std::move(filling_step)); } } void InterpreterSelectQuery::executeLimit(QueryPlan & query_plan) { auto & query = getSelectQuery(); /// If there is LIMIT if (query.limitLength()) { /** Rare case: * if there is no WITH TOTALS and there is a subquery in FROM, and there is WITH TOTALS on one of the levels, * then when using LIMIT, you should read the data to the end, rather than cancel the query earlier, * because if you cancel the query, we will not get `totals` data from the remote server. * * Another case: * if there is WITH TOTALS and there is no ORDER BY, then read the data to the end, * otherwise TOTALS is counted according to incomplete data. */ bool always_read_till_end = false; if (query.group_by_with_totals && !query.orderBy()) always_read_till_end = true; if (!query.group_by_with_totals && hasWithTotalsInAnySubqueryInFromClause(query)) always_read_till_end = true; UInt64 limit_length; UInt64 limit_offset; std::tie(limit_length, limit_offset) = getLimitLengthAndOffset(query, *context); SortDescription order_descr; if (query.limit_with_ties) { if (!query.orderBy()) throw Exception("LIMIT WITH TIES without ORDER BY", ErrorCodes::LOGICAL_ERROR); order_descr = getSortDescription(query, *context); } auto limit = std::make_unique( query_plan.getCurrentDataStream(), limit_length, limit_offset, always_read_till_end, query.limit_with_ties, order_descr); if (query.limit_with_ties) limit->setStepDescription("LIMIT WITH TIES"); query_plan.addStep(std::move(limit)); } } void InterpreterSelectQuery::executeOffset(QueryPlan & query_plan) { auto & query = getSelectQuery(); /// If there is not a LIMIT but an offset if (!query.limitLength() && query.limitOffset()) { UInt64 limit_length; UInt64 limit_offset; std::tie(limit_length, limit_offset) = getLimitLengthAndOffset(query, *context); auto offsets_step = std::make_unique(query_plan.getCurrentDataStream(), limit_offset); query_plan.addStep(std::move(offsets_step)); } } void InterpreterSelectQuery::executeExtremes(QueryPlan & query_plan) { if (!context->getSettingsRef().extremes) return; auto extremes_step = std::make_unique(query_plan.getCurrentDataStream()); query_plan.addStep(std::move(extremes_step)); } void InterpreterSelectQuery::executeSubqueriesInSetsAndJoins(QueryPlan & query_plan, SubqueriesForSets & subqueries_for_sets) { if (query_info.input_order_info) executeMergeSorted(query_plan, query_info.input_order_info->order_key_prefix_descr, 0, "before creating sets for subqueries and joins"); const Settings & settings = context->getSettingsRef(); SizeLimits limits(settings.max_rows_to_transfer, settings.max_bytes_to_transfer, settings.transfer_overflow_mode); addCreatingSetsStep(query_plan, std::move(subqueries_for_sets), limits, *context); } void InterpreterSelectQuery::ignoreWithTotals() { getSelectQuery().group_by_with_totals = false; } void InterpreterSelectQuery::initSettings() { auto & query = getSelectQuery(); if (query.settings()) InterpreterSetQuery(query.settings(), *context).executeForCurrentContext(); } }