#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 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 = std::make_shared(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(); auto column_name = expr_list->children.at(0)->getColumnName(); actions->removeUnusedActions(NameSet{column_name}); actions->projectInput(false); for (const auto * node : actions->getInputs()) actions->getIndex().push_back(node); return column_name; } InterpreterSelectQuery::InterpreterSelectQuery( const ASTPtr & query_ptr_, ContextPtr context_, const SelectQueryOptions & options_, const Names & required_result_column_names_) : InterpreterSelectQuery(query_ptr_, context_, std::nullopt, nullptr, options_, required_result_column_names_) { } InterpreterSelectQuery::InterpreterSelectQuery( const ASTPtr & query_ptr_, ContextPtr context_, const SelectQueryOptions & options_, PreparedSets prepared_sets_) : InterpreterSelectQuery(query_ptr_, context_, std::nullopt, nullptr, options_, {}, {}, std::move(prepared_sets_)) { } InterpreterSelectQuery::InterpreterSelectQuery( const ASTPtr & query_ptr_, ContextPtr context_, Pipe input_pipe_, const SelectQueryOptions & options_) : InterpreterSelectQuery(query_ptr_, context_, std::move(input_pipe_), nullptr, options_.copy().noSubquery()) {} InterpreterSelectQuery::InterpreterSelectQuery( const ASTPtr & query_ptr_, ContextPtr context_, const StoragePtr & storage_, const StorageMetadataPtr & metadata_snapshot_, const SelectQueryOptions & options_) : InterpreterSelectQuery(query_ptr_, context_, 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 ContextPtr getSubqueryContext(ContextPtr context) { auto subquery_context = Context::createCopy(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, const Settings & settings) { 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}; cross_to_inner.cross_to_inner_join_rewrite = settings.cross_to_inner_join_rewrite; 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( ContextPtr context, const StorageID & table_id, const StorageMetadataPtr & table_metadata, 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( ErrorCodes::ACCESS_DENIED, "{}: Not enough privileges. To execute this query it's necessary to have grant SELECT for at least one column on {}", context->getUserName(), table_id.getFullTableName()); } /// General check. context->checkAccess(AccessType::SELECT, table_id, syntax_analyzer_result.requiredSourceColumnsForAccessCheck()); } /// 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_, ContextPtr context_, std::optional input_pipe_, const StoragePtr & storage_, const SelectQueryOptions & options_, const Names & required_result_column_names, const StorageMetadataPtr & metadata_snapshot_, PreparedSets prepared_sets_) /// 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_pipe(std::move(input_pipe_)) , log(&Poco::Logger::get("InterpreterSelectQuery")) , metadata_snapshot(metadata_snapshot_) , prepared_sets(std::move(prepared_sets_)) { checkStackSize(); query_info.ignore_projections = options.ignore_projections; query_info.is_projection_query = options.is_projection_query; query_info.original_query = query_ptr->clone(); 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_pipe != std::nullopt; 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.is_subquery) { if (context->getSettingsRef().enable_global_with_statement) ApplyWithAliasVisitor().visit(query_ptr); ApplyWithSubqueryVisitor().visit(query_ptr); } JoinedTables joined_tables(getSubqueryContext(context), getSelectQuery(), options.with_all_cols); 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(), context->getSettingsRef()); 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); if (storage) row_policy_filter = context->getRowPolicyFilter(table_id.getDatabaseName(), table_id.getTableName(), RowPolicyFilterType::SELECT_FILTER); StorageView * view = nullptr; if (storage) view = dynamic_cast(storage.get()); /// Reuse already built sets for multiple passes of analysis 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); query_info.syntax_analyzer_result = syntax_analyzer_result; context->setDistributed(syntax_analyzer_result->is_remote_storage); if (storage && !query.final() && storage->needRewriteQueryWithFinal(syntax_analyzer_result->requiredSourceColumns())) query.setFinal(); /// 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 && storage->supportsPrewhere() && query.where() && !query.prewhere()) { /// PREWHERE optimization: transfer some condition from WHERE to PREWHERE if enabled and viable if (const auto & column_sizes = storage->getColumnSizes(); !column_sizes.empty()) { /// Extract column compressed sizes. std::unordered_map column_compressed_sizes; for (const auto & [name, sizes] : column_sizes) column_compressed_sizes[name] = sizes.data_compressed; SelectQueryInfo current_info; current_info.query = query_ptr; current_info.syntax_analyzer_result = syntax_analyzer_result; MergeTreeWhereOptimizer{ current_info, context, std::move(column_compressed_sizes), metadata_snapshot, syntax_analyzer_result->requiredSourceColumns(), log}; } } 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())); } 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), std::move(prepared_sets)); if (!options.only_analyze) { if (query.sampleSize() && (input_pipe || !storage || !storage->supportsSampling())) throw Exception("Illegal SAMPLE: table doesn't support sampling", ErrorCodes::SAMPLING_NOT_SUPPORTED); if (query.final() && (input_pipe || !storage || !storage->supportsFinal())) throw Exception( (!input_pipe && storage) ? "Storage " + storage->getName() + " doesn't support FINAL" : "Illegal FINAL", ErrorCodes::ILLEGAL_FINAL); if (query.prewhere() && (input_pipe || !storage || !storage->supportsPrewhere())) throw Exception( (!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) { /// Fix source_header for filter actions. if (row_policy_filter) { filter_info = std::make_shared(); filter_info->column_name = generateFilterActions(filter_info->actions, required_columns); auto required_columns_from_filter = filter_info->actions->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); } } source_header = metadata_snapshot->getSampleBlockForColumns(required_columns, storage->getVirtuals(), storage->getStorageID()); } /// Calculate structure of the result. result_header = getSampleBlockImpl(); }; analyze(shouldMoveToPrewhere()); 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 (need_analyze_again) { LOG_TRACE(log, "Running 'analyze' second time"); /// Reuse already built sets for multiple passes of analysis subquery_for_sets = std::move(query_analyzer->getSubqueriesForSets()); prepared_sets = query_info.sets.empty() ? std::move(query_analyzer->getPreparedSets()) : std::move(query_info.sets); /// 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, *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; } } /// Add prewhere actions with alias columns and record needed columns from storage. if (storage) { addPrewhereAliasActions(); analysis_result.required_columns = required_columns; } /// 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, 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(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 = QueryPipelineBuilder::getPipeline(std::move(*query_plan.buildQueryPipeline( QueryPlanOptimizationSettings::fromContext(context), BuildQueryPipelineSettings::fromContext(context)))); return res; } Block InterpreterSelectQuery::getSampleBlockImpl() { OpenTelemetrySpanHolder span(__PRETTY_FUNCTION__); query_info.query = query_ptr; query_info.has_window = query_analyzer->hasWindow(); if (storage && !options.only_analyze) { auto & query = getSelectQuery(); query_analyzer->makeSetsForIndex(query.where()); query_analyzer->makeSetsForIndex(query.prewhere()); query_info.sets = query_analyzer->getPreparedSets(); } if (storage && !options.only_analyze) from_stage = storage->getQueryProcessingStage(context, options.to_stage, metadata_snapshot, query_info); /// Do I need to perform the first part of the pipeline? /// Running on remote servers during distributed processing or if query is not distributed. /// /// Also note that with distributed_group_by_no_merge=1 or when there is /// only one remote server, it is equal to local query in terms of query /// stages (or when due to optimize_distributed_group_by_sharding_key the query was processed up to Complete stage). 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 or if query is not distributed. /// /// Also note that with distributed_group_by_no_merge=2 (i.e. when optimize_distributed_group_by_sharding_key takes place) /// the query on the remote server will be processed up to WithMergeableStateAfterAggregationAndLimit, /// So it will do partial second stage (second_stage=true), and initiator will do the final part. 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) { header = analysis_result.prewhere_info->prewhere_actions->updateHeader(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? // Here we calculate the header we want from remote server after it // executes query up to WithMergeableState. When there is an ORDER BY, // it is executed on remote server firstly, then we execute merge // sort on initiator. To execute ORDER BY, we need to calculate the // ORDER BY keys. These keys might be not present among the final // SELECT columns given by the `selected_column`. This is why we have // to use proper keys given by the result columns of the // `before_order_by` expression actions. // Another complication is window functions -- if we have them, they // are calculated on initiator, before ORDER BY columns. In this case, // the shard has to return columns required for window function // calculation and further steps, given by the `before_window` // expression actions. // As of 21.6 this is broken: the actions in `before_window` might // not contain everything required for the ORDER BY step, but this // is a responsibility of ExpressionAnalyzer and is not a problem // with this code. See // https://github.com/ClickHouse/ClickHouse/issues/19857 for details. if (analysis_result.before_window) return analysis_result.before_window->getResultColumns(); 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) { // It's different from selected_columns, see the comment above for // WithMergeableState stage. if (analysis_result.before_window) return analysis_result.before_window->getResultColumns(); return analysis_result.before_order_by->getResultColumns(); } return analysis_result.final_projection->getResultColumns(); } static Field getWithFillFieldValue(const ASTPtr & node, ContextPtr context) { 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 std::pair> getWithFillStep(const ASTPtr & node, ContextPtr context) { auto [field, type] = evaluateConstantExpression(node, context); if (const auto * type_interval = typeid_cast(type.get())) return std::make_pair(std::move(field), type_interval->getKind()); if (isColumnedAsNumber(type)) return std::make_pair(std::move(field), std::nullopt); throw Exception("Illegal type " + type->getName() + " of WITH FILL expression, must be numeric type", ErrorCodes::INVALID_WITH_FILL_EXPRESSION); } static FillColumnDescription getWithFillDescription(const ASTOrderByElement & order_by_elem, ContextPtr 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) std::tie(descr.fill_step, descr.step_kind) = getWithFillStep(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, ContextPtr 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, ContextPtr 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, ContextPtr 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, ContextPtr 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().first && 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()) { /** NOTE * 1. For ASTSelectWithUnionQuery after normalization for union child node the height of the AST tree is at most 2. * 2. For ASTSelectIntersectExceptQuery after normalization in case there are intersect or except nodes, * the height of the AST tree can have any depth (each intersect/except adds a level), but the * number of children in those nodes is always 2. */ std::function traverse_recursively = [&](ASTPtr child_ast) -> bool { if (const auto * select_child = child_ast->as ()) { if (hasWithTotalsInAnySubqueryInFromClause(select_child->as())) return true; } else if (const auto * union_child = child_ast->as()) { for (const auto & subchild : union_child->list_of_selects->children) if (traverse_recursively(subchild)) return true; } else if (const auto * intersect_child = child_ast->as()) { auto selects = intersect_child->getListOfSelects(); for (const auto & subchild : selects) if (traverse_recursively(subchild)) return true; } return false; }; for (const auto & elem : ast_union->list_of_selects->children) if (traverse_recursively(elem)) return true; } } return false; } void InterpreterSelectQuery::executeImpl(QueryPlan & query_plan, 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; /// 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; if (query_info.projection && query_info.projection->desc->type == ProjectionDescription::Type::Aggregate) { query_info.projection->aggregate_overflow_row = aggregate_overflow_row; query_info.projection->aggregate_final = aggregate_final; } if (options.only_analyze) { auto read_nothing = std::make_unique(source_header); query_plan.addStep(std::move(read_nothing)); if (expressions.filter_info) { auto row_level_security_step = std::make_unique( query_plan.getCurrentDataStream(), expressions.filter_info->actions, 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.prewhere_info) { if (expressions.prewhere_info->row_level_filter) { auto row_level_filter_step = std::make_unique( query_plan.getCurrentDataStream(), expressions.prewhere_info->row_level_filter, expressions.prewhere_info->row_level_column_name, false); row_level_filter_step->setStepDescription("Row-level security filter (PREWHERE)"); query_plan.addStep(std::move(row_level_filter_step)); } 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)); } } 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; /// Read the data from Storage. from_stage - to what stage the request was completed in Storage. executeFetchColumns(from_stage, query_plan); LOG_TRACE(log, "{} -> {}", QueryProcessingStage::toString(from_stage), QueryProcessingStage::toString(options.to_stage)); } if (options.to_stage > QueryProcessingStage::FetchColumns) { 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() && !expressions.has_window) { if (expressions.has_order_by) executeOrder( query_plan, query_info.input_order_info ? query_info.input_order_info : (query_info.projection ? query_info.projection->input_order_info : nullptr)); 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 there is a storage that supports prewhere, this will always be nullptr // Thus, we don't actually need to check if projection is active. if (!query_info.projection && expressions.filter_info) { auto row_level_security_step = std::make_unique( query_plan.getCurrentDataStream(), expressions.filter_info->actions, 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)); } /// Optional step to convert key columns to common supertype. if (expressions.converting_join_columns) { QueryPlanStepPtr convert_join_step = std::make_unique( query_plan.getCurrentDataStream(), expressions.converting_join_columns); convert_join_step->setStepDescription("Convert JOIN columns"); query_plan.addStep(std::move(convert_join_step)); } if (expressions.hasJoin()) { if (expressions.join->isFilled()) { QueryPlanStepPtr filled_join_step = std::make_unique( query_plan.getCurrentDataStream(), expressions.join, settings.max_block_size); filled_join_step->setStepDescription("JOIN"); query_plan.addStep(std::move(filled_join_step)); } else { auto joined_plan = query_analyzer->getJoinedPlan(); if (!joined_plan) throw Exception(ErrorCodes::LOGICAL_ERROR, "There is no joined plan for query"); QueryPlanStepPtr join_step = std::make_unique( query_plan.getCurrentDataStream(), joined_plan->getCurrentDataStream(), expressions.join, settings.max_block_size); join_step->setStepDescription("JOIN"); std::vector plans; plans.emplace_back(std::make_unique(std::move(query_plan))); plans.emplace_back(std::move(joined_plan)); query_plan = QueryPlan(); query_plan.unitePlans(std::move(join_step), {std::move(plans)}); } } if (!query_info.projection && 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(); } // Now we must execute: // 1) expressions before window functions, // 2) window functions, // 3) expressions after window functions, // 4) preliminary distinct. // This code decides which part we execute on shard (first_stage) // and which part on initiator (second_stage). See also the counterpart // code for "second_stage" that has to execute the rest. if (expressions.need_aggregate) { // We have aggregation, so we can't execute any later-stage // expressions on shards, neither "before window functions" nor // "before ORDER BY". } else { // We don't have aggregation. // Window functions must be executed on initiator (second_stage). // ORDER BY and DISTINCT might depend on them, so if we have // window functions, we can't execute ORDER BY and DISTINCT // now, on shard (first_stage). if (query_analyzer->hasWindow()) { executeExpression(query_plan, expressions.before_window, "Before window functions"); } else { // We don't have window functions, so we can execute the // expressions before ORDER BY and the preliminary DISTINCT // now, on shards (first_stage). assert(!expressions.before_window); 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, expressions.remove_having_filter, 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, expressions.remove_having_filter); } } else if (expressions.hasHaving()) executeHaving(query_plan, expressions.before_having, expressions.remove_having_filter); } 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); // Now we must execute: // 1) expressions before window functions, // 2) window functions, // 3) expressions after window functions, // 4) preliminary distinct. // Some of these were already executed at the shards (first_stage), // see the counterpart code and comments there. if (from_aggregation_stage) { if (query_analyzer->hasWindow()) throw Exception( "Window functions does not support processing from WithMergeableStateAfterAggregation", ErrorCodes::NOT_IMPLEMENTED); } else if (expressions.need_aggregate) { 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_analyzer->hasWindow()) { executeWindow(query_plan); executeExpression(query_plan, expressions.before_order_by, "Before ORDER BY"); executeDistinct(query_plan, true, expressions.selected_columns, true); } else { // Neither aggregation nor windows, all expressions before // ORDER BY executed on shards. } } 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. * * Also in case of remote servers was process the query up to WithMergeableStateAfterAggregationAndLimit * (distributed_group_by_no_merge=2 or optimize_distributed_group_by_sharding_key=1 takes place), * then merge the sorted streams is enough, since remote servers already did full ORDER BY. */ if (from_aggregation_stage) executeMergeSorted(query_plan, "after aggregation stage for ORDER BY"); else if (!expressions.first_stage && !expressions.need_aggregate && !expressions.has_window && !(query.group_by_with_totals && !aggregate_final)) executeMergeSorted(query_plan, "for ORDER BY, without aggregation"); else /// Otherwise, just sort. executeOrder( query_plan, query_info.input_order_info ? query_info.input_order_info : (query_info.projection ? query_info.projection->input_order_info : nullptr)); } /** 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 apply_limit = options.to_stage != QueryProcessingStage::WithMergeableStateAfterAggregation; bool apply_prelimit = apply_limit && query.limitLength() && !query.limit_with_ties && !hasWithTotalsInAnySubqueryInFromClause(query) && !query.arrayJoinExpressionList().first && !query.distinct && !expressions.hasLimitBy() && !settings.extremes && !has_withfill; bool apply_offset = options.to_stage != QueryProcessingStage::WithMergeableStateAfterAggregationAndLimit; if (apply_prelimit) { executePreLimit(query_plan, /* do_not_skip_offset= */!apply_offset); } /** If there was more than one stream, * then DISTINCT needs to be performed once again after merging all streams. */ if (!from_aggregation_stage && query.distinct) executeDistinct(query_plan, false, expressions.selected_columns, false); if (!from_aggregation_stage && 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 && apply_offset) { executeLimit(query_plan); } /// Projection not be done on the shards, since then initiator will not find column in blocks. /// (significant only for WithMergeableStateAfterAggregation/WithMergeableStateAfterAggregationAndLimit). 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); bool limit_applied = apply_prelimit || (query.limit_with_ties && apply_offset); /// Limit is no longer needed if there is prelimit. /// /// NOTE: that LIMIT cannot be applied if OFFSET should not be applied, /// since LIMIT will apply OFFSET too. /// This is the case for various optimizations for distributed queries, /// and when LIMIT cannot be applied it will be applied on the initiator anyway. if (apply_limit && !limit_applied && apply_offset) executeLimit(query_plan); if (apply_offset) 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; } static void executeMergeAggregatedImpl( QueryPlan & query_plan, bool overflow_row, bool final, bool is_remote_storage, const Settings & settings, const NamesAndTypesList & aggregation_keys, const AggregateDescriptions & aggregates) { const auto & header_before_merge = query_plan.getCurrentDataStream().header; ColumnNumbers keys; for (const auto & key : aggregation_keys) 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. */ Aggregator::Params params(header_before_merge, keys, 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 && is_remote_storage, settings.max_threads, settings.aggregation_memory_efficient_merge_threads); query_plan.addStep(std::move(merging_aggregated)); } void InterpreterSelectQuery::addEmptySourceToQueryPlan( QueryPlan & query_plan, const Block & source_header, const SelectQueryInfo & query_info, ContextPtr context_) { Pipe pipe(std::make_shared(source_header)); PrewhereInfoPtr prewhere_info_ptr = query_info.projection ? query_info.projection->prewhere_info : query_info.prewhere_info; if (prewhere_info_ptr) { auto & prewhere_info = *prewhere_info_ptr; if (prewhere_info.alias_actions) { pipe.addSimpleTransform([&](const Block & header) { return std::make_shared(header, std::make_shared(prewhere_info.alias_actions)); }); } if (prewhere_info.row_level_filter) { pipe.addSimpleTransform([&](const Block & header) { return std::make_shared(header, std::make_shared(prewhere_info.row_level_filter), prewhere_info.row_level_column_name, true); }); } pipe.addSimpleTransform([&](const Block & header) { return std::make_shared( header, std::make_shared(prewhere_info.prewhere_actions), prewhere_info.prewhere_column_name, prewhere_info.remove_prewhere_column); }); } 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)); if (query_info.projection) { if (query_info.projection->before_where) { auto where_step = std::make_unique( query_plan.getCurrentDataStream(), query_info.projection->before_where, query_info.projection->where_column_name, query_info.projection->remove_where_filter); where_step->setStepDescription("WHERE"); query_plan.addStep(std::move(where_step)); } if (query_info.projection->desc->type == ProjectionDescription::Type::Aggregate) { if (query_info.projection->before_aggregation) { auto expression_before_aggregation = std::make_unique(query_plan.getCurrentDataStream(), query_info.projection->before_aggregation); expression_before_aggregation->setStepDescription("Before GROUP BY"); query_plan.addStep(std::move(expression_before_aggregation)); } executeMergeAggregatedImpl( query_plan, query_info.projection->aggregate_overflow_row, query_info.projection->aggregate_final, false, context_->getSettingsRef(), query_info.projection->aggregation_keys, query_info.projection->aggregate_descriptions); } } } bool InterpreterSelectQuery::shouldMoveToPrewhere() { const Settings & settings = context->getSettingsRef(); const ASTSelectQuery & query = getSelectQuery(); return settings.optimize_move_to_prewhere && (!query.final() || settings.optimize_move_to_prewhere_if_final); } void InterpreterSelectQuery::addPrewhereAliasActions() { auto & expressions = analysis_result; if (expressions.filter_info) { if (!expressions.prewhere_info) { const bool does_storage_support_prewhere = !input_pipe && storage && storage->supportsPrewhere(); if (does_storage_support_prewhere && shouldMoveToPrewhere()) { /// Execute row level filter in prewhere as a part of "move to prewhere" optimization. expressions.prewhere_info = std::make_shared( std::move(expressions.filter_info->actions), std::move(expressions.filter_info->column_name)); expressions.prewhere_info->prewhere_actions->projectInput(false); expressions.prewhere_info->remove_prewhere_column = expressions.filter_info->do_remove_column; expressions.prewhere_info->need_filter = true; expressions.filter_info = nullptr; } } else { /// Add row level security actions to prewhere. expressions.prewhere_info->row_level_filter = std::move(expressions.filter_info->actions); expressions.prewhere_info->row_level_column_name = std::move(expressions.filter_info->column_name); expressions.prewhere_info->row_level_filter->projectInput(false); expressions.filter_info = nullptr; } } auto & prewhere_info = analysis_result.prewhere_info; auto & columns_to_remove_after_prewhere = analysis_result.columns_to_remove_after_prewhere; /// 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()); if (prewhere_info->row_level_filter) { auto row_level_required_columns = prewhere_info->row_level_filter->getRequiredColumns().getNames(); required_columns_from_prewhere.insert(row_level_required_columns.begin(), row_level_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->array_join_result_to_source, 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 = collections::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. std::erase_if(required_columns, [&](const String & name) { return required_columns_after_prewhere_set.count(name) != 0; }); 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); } } } void InterpreterSelectQuery::executeFetchColumns(QueryProcessingStage::Enum processing_stage, QueryPlan & query_plan) { 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() != "MaterializedMySQL" && !row_policy_filter && 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) { const 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_MEMORY_SAFE(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 source = std::make_shared(block_with_count); auto prepared_count = std::make_unique(Pipe(std::move(source)), context); prepared_count->setStepDescription("Optimized trivial count"); query_plan.addStep(std::move(prepared_count)); from_stage = QueryProcessingStage::WithMergeableState; analysis_result.first_stage = false; return; } } /// 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( ErrorCodes::TOO_MANY_COLUMNS, "Limit for number of columns to read exceeded. Requested: {}, maximum: {}", required_columns.size(), settings.max_columns_to_read); /// 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() && !query_analyzer->hasWindow() && 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) max_streams = 1; /// 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; auto & prewhere_info = analysis_result.prewhere_info; if (prewhere_info) query_info.prewhere_info = prewhere_info; /// 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) && (!query_info.projection || query_info.projection->complete)) { if (analysis_result.optimize_read_in_order) { if (query_info.projection) { query_info.projection->order_optimizer = std::make_shared( // TODO Do we need a projection variant for this field? analysis_result.order_by_elements_actions, getSortDescription(query, context), query_info.syntax_analyzer_result); } else { query_info.order_optimizer = std::make_shared( analysis_result.order_by_elements_actions, getSortDescription(query, context), query_info.syntax_analyzer_result); } } else { if (query_info.projection) { query_info.projection->order_optimizer = std::make_shared( query_info.projection->group_by_elements_actions, getSortDescriptionFromGroupBy(query), 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); } } /// If we don't have filtration, we can pushdown limit to reading stage for optimizations. UInt64 limit = (query.hasFiltration() || query.groupBy()) ? 0 : getLimitForSorting(query, context); if (query_info.projection) query_info.projection->input_order_info = query_info.projection->order_optimizer->getInputOrder(query_info.projection->desc->metadata, context, limit); else query_info.input_order_info = query_info.order_optimizer->getInputOrder(metadata_snapshot, context, limit); } 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) { const String view_name{}; auto local_storage_id = storage->getStorageID(); context->getQueryContext()->addQueryAccessInfo( backQuoteIfNeed(local_storage_id.getDatabaseName()), local_storage_id.getFullTableName(), required_columns, query_info.projection ? query_info.projection->desc->name : "", view_name); } /// Create step which reads from empty source if storage has no data. if (!query_plan.isInitialized()) { auto header = query_info.projection ? query_info.projection->desc->metadata->getSampleBlockForColumns( query_info.projection->required_columns, storage->getVirtuals(), storage->getStorageID()) : metadata_snapshot->getSampleBlockForColumns(required_columns, storage->getVirtuals(), storage->getStorageID()); addEmptySourceToQueryPlan(query_plan, header, query_info, context); } /// 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)); if (options.is_projection_query) return; 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 || (settings.empty_result_for_aggregation_by_constant_keys_on_empty_set && keys.empty() && query_analyzer->hasConstAggregationKeys()), context->getTemporaryVolume(), settings.max_threads, settings.min_free_disk_space_for_temporary_data, settings.compile_aggregate_expressions, settings.min_count_to_compile_aggregate_expression); 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, settings.aggregation_in_order_max_block_bytes, 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) { /// If aggregate projection was chosen for table, avoid adding MergeAggregated. /// It is already added by storage (because of performance issues). /// TODO: We should probably add another one processing stage for storage? /// WithMergeableStateAfterAggregation is not ok because, e.g., it skips sorting after aggregation. if (query_info.projection && query_info.projection->desc->type == ProjectionDescription::Type::Aggregate) return; executeMergeAggregatedImpl( query_plan, overflow_row, final, storage && storage->isRemote(), context->getSettingsRef(), query_analyzer->aggregationKeys(), query_analyzer->aggregates()); } void InterpreterSelectQuery::executeHaving(QueryPlan & query_plan, const ActionsDAGPtr & expression, bool remove_filter) { auto having_step = std::make_unique(query_plan.getCurrentDataStream(), expression, getSelectQuery().having()->getColumnName(), remove_filter); having_step->setStepDescription("HAVING"); query_plan.addStep(std::move(having_step)); } void InterpreterSelectQuery::executeTotalsAndHaving( QueryPlan & query_plan, bool has_having, const ActionsDAGPtr & expression, bool remove_filter, 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() : "", remove_filter, 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, settings.compile_aggregate_expressions, settings.min_count_to_compile_aggregate_expression); 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)); } static bool windowDescriptionComparator(const WindowDescription * _left, const WindowDescription * _right) { const auto & left = _left->full_sort_description; const auto & right = _right->full_sort_description; for (size_t i = 0; i < std::min(left.size(), right.size()); ++i) { if (left[i].column_name < right[i].column_name) return true; else if (left[i].column_name > right[i].column_name) return false; else if (left[i].column_number < right[i].column_number) return true; else if (left[i].column_number > right[i].column_number) return false; else if (left[i].direction < right[i].direction) return true; else if (left[i].direction > right[i].direction) return false; else if (left[i].nulls_direction < right[i].nulls_direction) return true; else if (left[i].nulls_direction > right[i].nulls_direction) return false; assert(left[i] == right[i]); } // Note that we check the length last, because we want to put together the // sort orders that have common prefix but different length. return left.size() > right.size(); } static bool sortIsPrefix(const WindowDescription & _prefix, const WindowDescription & _full) { const auto & prefix = _prefix.full_sort_description; const auto & full = _full.full_sort_description; if (prefix.size() > full.size()) return false; for (size_t i = 0; i < prefix.size(); ++i) { if (full[i] != prefix[i]) return false; } return true; } void InterpreterSelectQuery::executeWindow(QueryPlan & query_plan) { // Try to sort windows in such an order that the window with the longest // sort description goes first, and all window that use its prefixes follow. std::vector windows_sorted; for (const auto & [_, w] : query_analyzer->windowDescriptions()) windows_sorted.push_back(&w); std::sort(windows_sorted.begin(), windows_sorted.end(), windowDescriptionComparator); const Settings & settings = context->getSettingsRef(); for (size_t i = 0; i < windows_sorted.size(); ++i) { const auto & w = *windows_sorted[i]; // We don't need to sort again if the input from previous window already // has suitable sorting. Also don't create sort steps when there are no // columns to sort by, because the sort nodes are confused by this. It // happens in case of `over ()`. if (!w.full_sort_description.empty() && (i == 0 || !sortIsPrefix(w, *windows_sorted[i - 1]))) { auto sorting_step = std::make_unique( query_plan.getCurrentDataStream(), w.full_sort_description, settings.max_block_size, 0 /* LIMIT */, SizeLimits(settings.max_rows_to_sort, settings.max_bytes_to_sort, settings.sort_overflow_mode), 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); sorting_step->setStepDescription("Sorting for window '" + w.window_name + "'"); query_plan.addStep(std::move(sorting_step)); } 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(); /// Merge the sorted blocks. auto sorting_step = std::make_unique( query_plan.getCurrentDataStream(), output_order_descr, settings.max_block_size, limit, SizeLimits(settings.max_rows_to_sort, settings.max_bytes_to_sort, settings.sort_overflow_mode), 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); sorting_step->setStepDescription("Sorting for ORDER BY"); query_plan.addStep(std::move(sorting_step)); } 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); if (do_not_skip_offset) limit->setStepDescription("preliminary LIMIT (with OFFSET)"); else limit->setStepDescription("preliminary LIMIT (without OFFSET)"); 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) { const auto & input_order_info = query_info.input_order_info ? query_info.input_order_info : (query_info.projection ? query_info.projection->input_order_info : nullptr); if (input_order_info) executeMergeSorted(query_plan, 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(); auto & client_info = context->getClientInfo(); auto min_major = DBMS_MIN_MAJOR_VERSION_WITH_CURRENT_AGGREGATION_VARIANT_SELECTION_METHOD; auto min_minor = DBMS_MIN_MINOR_VERSION_WITH_CURRENT_AGGREGATION_VARIANT_SELECTION_METHOD; if (client_info.query_kind == ClientInfo::QueryKind::SECONDARY_QUERY && std::forward_as_tuple(client_info.connection_client_version_major, client_info.connection_client_version_minor) < std::forward_as_tuple(min_major, min_minor)) { /// Disable two-level aggregation due to version incompatibility. context->setSetting("group_by_two_level_threshold", Field(0)); context->setSetting("group_by_two_level_threshold_bytes", Field(0)); } } }