#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 EMPTY_NESTED_TABLE; extern const int LOGICAL_ERROR; extern const int INVALID_JOIN_ON_EXPRESSION; } NameSet removeDuplicateColumns(NamesAndTypesList & columns) { NameSet names; for (auto it = columns.begin(); it != columns.end();) { if (names.emplace(it->name).second) ++it; else columns.erase(it++); } return names; } namespace { using LogAST = DebugASTLog; /// set to true to enable logs /// Add columns from storage to source_columns list. void collectSourceColumns(const ASTSelectQuery * select_query, StoragePtr storage, NamesAndTypesList & source_columns) { if (storage) { auto physical_columns = storage->getColumns().getAllPhysical(); if (source_columns.empty()) source_columns.swap(physical_columns); else source_columns.insert(source_columns.end(), physical_columns.begin(), physical_columns.end()); if (select_query) { const auto & storage_aliases = storage->getColumns().aliases; source_columns.insert(source_columns.end(), storage_aliases.begin(), storage_aliases.end()); } } } /// Translate qualified names such as db.table.column, table.column, table_alias.column to names' normal form. /// Expand asterisks and qualified asterisks with column names. /// There would be columns in normal form & column aliases after translation. Column & column alias would be normalized in QueryNormalizer. void translateQualifiedNames(ASTPtr & query, const ASTSelectQuery & select_query, const Context & context, const Names & source_columns_list, const NameSet & source_columns_set, const JoinedColumnsList & columns_from_joined_table) { std::vector tables_with_columns = getDatabaseAndTablesWithColumnNames(select_query, context); if (tables_with_columns.empty()) { Names all_columns_name = source_columns_list; /// TODO: asterisk_left_columns_only probably does not work in some cases if (!context.getSettingsRef().asterisk_left_columns_only) { for (auto & column : columns_from_joined_table) all_columns_name.emplace_back(column.name_and_type.name); } tables_with_columns.emplace_back(DatabaseAndTableWithAlias{}, std::move(all_columns_name)); } LogAST log; TranslateQualifiedNamesVisitor::Data visitor_data(source_columns_set, tables_with_columns); TranslateQualifiedNamesVisitor visitor(visitor_data, log.stream()); visitor.visit(query); } bool hasArrayJoin(const ASTPtr & ast) { if (const ASTFunction * function = ast->as()) if (function->name == "arrayJoin") return true; for (const auto & child : ast->children) if (!child->as() && hasArrayJoin(child)) return true; return false; } /// Sometimes we have to calculate more columns in SELECT clause than will be returned from query. /// This is the case when we have DISTINCT or arrayJoin: we require more columns in SELECT even if we need less columns in result. void removeUnneededColumnsFromSelectClause(const ASTSelectQuery * select_query, const Names & required_result_columns) { if (required_result_columns.empty()) return; ASTs & elements = select_query->select_expression_list->children; ASTs new_elements; new_elements.reserve(elements.size()); /// Some columns may be queried multiple times, like SELECT x, y, y FROM table. /// In that case we keep them exactly same number of times. std::map required_columns_with_duplicate_count; for (const auto & name : required_result_columns) ++required_columns_with_duplicate_count[name]; for (const auto & elem : elements) { String name = elem->getAliasOrColumnName(); auto it = required_columns_with_duplicate_count.find(name); if (required_columns_with_duplicate_count.end() != it && it->second) { new_elements.push_back(elem); --it->second; } else if (select_query->distinct || hasArrayJoin(elem)) { new_elements.push_back(elem); } } elements = std::move(new_elements); } /// Replacing scalar subqueries with constant values. void executeScalarSubqueries(ASTPtr & query, const Context & context, size_t subquery_depth) { LogAST log; ExecuteScalarSubqueriesVisitor::Data visitor_data{context, subquery_depth}; ExecuteScalarSubqueriesVisitor(visitor_data, log.stream()).visit(query); } /** Calls to these functions in the GROUP BY statement would be * replaced by their immediate argument. */ const std::unordered_set injective_function_names { "negate", "bitNot", "reverse", "reverseUTF8", "toString", "toFixedString", "IPv4NumToString", "IPv4StringToNum", "hex", "unhex", "bitmaskToList", "bitmaskToArray", "tuple", "regionToName", "concatAssumeInjective", }; const std::unordered_set possibly_injective_function_names { "dictGetString", "dictGetUInt8", "dictGetUInt16", "dictGetUInt32", "dictGetUInt64", "dictGetInt8", "dictGetInt16", "dictGetInt32", "dictGetInt64", "dictGetFloat32", "dictGetFloat64", "dictGetDate", "dictGetDateTime" }; /// Eliminates injective function calls and constant expressions from group by statement. void optimizeGroupBy(ASTSelectQuery * select_query, const NameSet & source_columns, const Context & context) { if (!select_query->group_expression_list) return; const auto is_literal = [] (const ASTPtr & ast) -> bool { return ast->as(); }; auto & group_exprs = select_query->group_expression_list->children; /// removes expression at index idx by making it last one and calling .pop_back() const auto remove_expr_at_index = [&group_exprs] (const size_t idx) { if (idx < group_exprs.size() - 1) std::swap(group_exprs[idx], group_exprs.back()); group_exprs.pop_back(); }; /// iterate over each GROUP BY expression, eliminate injective function calls and literals for (size_t i = 0; i < group_exprs.size();) { if (const auto * function = group_exprs[i]->as()) { /// assert function is injective if (possibly_injective_function_names.count(function->name)) { /// do not handle semantic errors here if (function->arguments->children.size() < 2) { ++i; continue; } const auto & dict_name = function->arguments->children[0]->as()->value.safeGet(); const auto & dict_ptr = context.getExternalDictionaries().getDictionary(dict_name); const auto & attr_name = function->arguments->children[1]->as()->value.safeGet(); if (!dict_ptr->isInjective(attr_name)) { ++i; continue; } } else if (!injective_function_names.count(function->name)) { ++i; continue; } /// copy shared pointer to args in order to ensure lifetime auto args_ast = function->arguments; /** remove function call and take a step back to ensure * next iteration does not skip not yet processed data */ remove_expr_at_index(i); /// copy non-literal arguments std::remove_copy_if( std::begin(args_ast->children), std::end(args_ast->children), std::back_inserter(group_exprs), is_literal ); } else if (is_literal(group_exprs[i])) { remove_expr_at_index(i); } else { /// if neither a function nor literal - advance to next expression ++i; } } if (group_exprs.empty()) { /** You can not completely remove GROUP BY. Because if there were no aggregate functions, then it turns out that there will be no aggregation. * Instead, leave `GROUP BY const`. * Next, see deleting the constants in the analyzeAggregation method. */ /// You must insert a constant that is not the name of the column in the table. Such a case is rare, but it happens. UInt64 unused_column = 0; String unused_column_name = toString(unused_column); while (source_columns.count(unused_column_name)) { ++unused_column; unused_column_name = toString(unused_column); } select_query->group_expression_list = std::make_shared(); select_query->group_expression_list->children.emplace_back(std::make_shared(UInt64(unused_column))); } } /// Remove duplicate items from ORDER BY. void optimizeOrderBy(const ASTSelectQuery * select_query) { if (!select_query->order_expression_list) return; /// Make unique sorting conditions. using NameAndLocale = std::pair; std::set elems_set; ASTs & elems = select_query->order_expression_list->children; ASTs unique_elems; unique_elems.reserve(elems.size()); for (const auto & elem : elems) { String name = elem->children.front()->getColumnName(); const auto * order_by_elem = elem->as(); if (elems_set.emplace(name, order_by_elem->collation ? order_by_elem->collation->getColumnName() : "").second) unique_elems.emplace_back(elem); } if (unique_elems.size() < elems.size()) elems = unique_elems; } /// Remove duplicate items from LIMIT BY. void optimizeLimitBy(const ASTSelectQuery * select_query) { if (!select_query->limit_by_expression_list) return; std::set elems_set; ASTs & elems = select_query->limit_by_expression_list->children; ASTs unique_elems; unique_elems.reserve(elems.size()); for (const auto & elem : elems) { if (elems_set.emplace(elem->getColumnName()).second) unique_elems.emplace_back(elem); } if (unique_elems.size() < elems.size()) elems = unique_elems; } /// Remove duplicated columns from USING(...). void optimizeUsing(const ASTSelectQuery * select_query) { const auto * node = select_query->join()->as(); if (!node) return; const auto * table_join = node->table_join->as(); if (!(table_join && table_join->using_expression_list)) return; ASTs & expression_list = table_join->using_expression_list->children; ASTs uniq_expressions_list; std::set expressions_names; for (const auto & expression : expression_list) { auto expression_name = expression->getAliasOrColumnName(); if (expressions_names.find(expression_name) == expressions_names.end()) { uniq_expressions_list.push_back(expression); expressions_names.insert(expression_name); } } if (uniq_expressions_list.size() < expression_list.size()) expression_list = uniq_expressions_list; } void getArrayJoinedColumns(ASTPtr & query, SyntaxAnalyzerResult & result, const ASTSelectQuery * select_query, const Names & source_columns, const NameSet & source_columns_set) { if (ASTPtr array_join_expression_list = select_query->array_join_expression_list()) { ArrayJoinedColumnsVisitor::Data visitor_data{result.aliases, result.array_join_name_to_alias, result.array_join_alias_to_name, result.array_join_result_to_source}; ArrayJoinedColumnsVisitor(visitor_data).visit(query); /// If the result of ARRAY JOIN is not used, it is necessary to ARRAY-JOIN any column, /// to get the correct number of rows. if (result.array_join_result_to_source.empty()) { ASTPtr expr = select_query->array_join_expression_list()->children.at(0); String source_name = expr->getColumnName(); String result_name = expr->getAliasOrColumnName(); /// This is an array. if (!expr->as() || source_columns_set.count(source_name)) { result.array_join_result_to_source[result_name] = source_name; } else /// This is a nested table. { bool found = false; for (const auto & column_name : source_columns) { auto splitted = Nested::splitName(column_name); if (splitted.first == source_name && !splitted.second.empty()) { result.array_join_result_to_source[Nested::concatenateName(result_name, splitted.second)] = column_name; found = true; break; } } if (!found) throw Exception("No columns in nested table " + source_name, ErrorCodes::EMPTY_NESTED_TABLE); } } } } /// Parse JOIN ON expression and collect ASTs for joined columns. void collectJoinedColumnsFromJoinOnExpr(AnalyzedJoin & analyzed_join, const ASTTableJoin & table_join) { if (!table_join.on_expression) return; /// Stores examples of columns which are only from one table. struct TableBelonging { const ASTIdentifier * example_only_from_left = nullptr; const ASTIdentifier * example_only_from_right = nullptr; }; /// Check all identifiers in ast and decide their possible table belonging. /// Throws if there are two identifiers definitely from different tables. std::function get_table_belonging; get_table_belonging = [&](const ASTPtr & ast) -> TableBelonging { if (IdentifierSemantic::getColumnName(ast)) { const auto * identifier = ast->as(); /// It's set in TranslateQualifiedNamesVisitor size_t membership = IdentifierSemantic::getMembership(*identifier); switch (membership) { case 1: return {identifier, nullptr}; case 2: return {nullptr, identifier}; default: break; } return {}; } TableBelonging table_belonging; for (const auto & child : ast->children) { auto children_belonging = get_table_belonging(child); if (!table_belonging.example_only_from_left) table_belonging.example_only_from_left = children_belonging.example_only_from_left; if (!table_belonging.example_only_from_right) table_belonging.example_only_from_right = children_belonging.example_only_from_right; } if (table_belonging.example_only_from_left && table_belonging.example_only_from_right) throw Exception("Invalid columns in JOIN ON section. Columns " + table_belonging.example_only_from_left->getAliasOrColumnName() + " and " + table_belonging.example_only_from_right->getAliasOrColumnName() + " are from different tables.", ErrorCodes::INVALID_JOIN_ON_EXPRESSION); return table_belonging; }; const auto supported_syntax = " Supported syntax: JOIN ON Expr([table.]column, ...) = Expr([table.]column, ...) " "[AND Expr([table.]column, ...) = Expr([table.]column, ...) ...]"; auto throwSyntaxException = [&](const String & msg) { throw Exception("Invalid expression for JOIN ON. " + msg + supported_syntax, ErrorCodes::INVALID_JOIN_ON_EXPRESSION); }; /// For equal expression find out corresponding table for each part, translate qualified names and add asts to join keys. auto add_columns_from_equals_expr = [&](const ASTPtr & expr) { const auto * func_equals = expr->as(); if (!func_equals || func_equals->name != "equals") throwSyntaxException("Expected equals expression, got " + queryToString(expr) + "."); ASTPtr left_ast = func_equals->arguments->children.at(0)->clone(); ASTPtr right_ast = func_equals->arguments->children.at(1)->clone(); auto left_table_belonging = get_table_belonging(left_ast); auto right_table_belonging = get_table_belonging(right_ast); bool can_be_left_part_from_left_table = left_table_belonging.example_only_from_right == nullptr; bool can_be_left_part_from_right_table = left_table_belonging.example_only_from_left == nullptr; bool can_be_right_part_from_left_table = right_table_belonging.example_only_from_right == nullptr; bool can_be_right_part_from_right_table = right_table_belonging.example_only_from_left == nullptr; /// Default variant when all identifiers may be from any table. if (can_be_left_part_from_left_table && can_be_right_part_from_right_table) analyzed_join.addOnKeys(left_ast, right_ast); else if (can_be_left_part_from_right_table && can_be_right_part_from_left_table) analyzed_join.addOnKeys(right_ast, left_ast); else { auto * left_example = left_table_belonging.example_only_from_left ? left_table_belonging.example_only_from_left : left_table_belonging.example_only_from_right; auto * right_example = right_table_belonging.example_only_from_left ? right_table_belonging.example_only_from_left : right_table_belonging.example_only_from_right; auto left_name = queryToString(*left_example); auto right_name = queryToString(*right_example); auto expr_name = queryToString(expr); throwSyntaxException("In expression " + expr_name + " columns " + left_name + " and " + right_name + " are from the same table but from different arguments of equal function."); } }; const auto * func = table_join.on_expression->as(); if (func && func->name == "and") { for (const auto & expr : func->arguments->children) add_columns_from_equals_expr(expr); } else add_columns_from_equals_expr(table_join.on_expression); } /// Find the columns that are obtained by JOIN. void collectJoinedColumns(AnalyzedJoin & analyzed_join, const ASTSelectQuery & select_query, const NameSet & source_columns, const String & current_database, bool join_use_nulls) { const ASTTablesInSelectQueryElement * node = select_query.join(); if (!node) return; const auto * table_join = node->table_join->as(); const auto * table_expression = node->table_expression->as(); DatabaseAndTableWithAlias joined_table_name(*table_expression, current_database); if (table_join->using_expression_list) { const auto * keys = table_join->using_expression_list->as(); for (const auto & key : keys->children) analyzed_join.addUsingKey(key); for (auto & name : analyzed_join.key_names_right) if (source_columns.count(name)) name = joined_table_name.getQualifiedNamePrefix() + name; } else if (table_join->on_expression) collectJoinedColumnsFromJoinOnExpr(analyzed_join, *table_join); bool make_nullable = join_use_nulls && (table_join->kind == ASTTableJoin::Kind::Left || table_join->kind == ASTTableJoin::Kind::Full); analyzed_join.calculateAvailableJoinedColumns(make_nullable); } Names qualifyOccupiedNames(NamesAndTypesList & columns, const NameSet & source_columns, const DatabaseAndTableWithAlias& table) { Names originals; originals.reserve(columns.size()); for (auto & column : columns) { originals.push_back(column.name); if (source_columns.count(column.name)) column.name = table.getQualifiedNamePrefix() + column.name; } return originals; } void replaceJoinedTable(const ASTTablesInSelectQueryElement* join) { if (!join || !join->table_expression) return; const auto * table_expr = join->table_expression->as(); if (table_expr->database_and_table_name) { const auto * table_id = table_expr->database_and_table_name->as(); String expr = "(select * from " + table_id->name + ") as " + table_id->shortName(); // FIXME: since the expression "a as b" exposes both "a" and "b" names, which is not equivalent to "(select * from a) as b", // we can't replace aliased tables. // FIXME: long table names include database name, which we can't save within alias. if (table_id->alias.empty() && table_id->isShort()) { ParserTableExpression parser; table_expr = parseQuery(parser, expr, 0)->as(); } } } } // namespace SyntaxAnalyzerResultPtr SyntaxAnalyzer::analyze( ASTPtr & query, const NamesAndTypesList & source_columns_, const Names & required_result_columns, StoragePtr storage) const { auto * select_query = query->as(); if (!storage && select_query) { if (auto db_and_table = getDatabaseAndTable(*select_query, 0)) storage = context.tryGetTable(db_and_table->database, db_and_table->table); } SyntaxAnalyzerResult result; result.storage = storage; result.source_columns = source_columns_; collectSourceColumns(select_query, result.storage, result.source_columns); NameSet source_columns_set = removeDuplicateColumns(result.source_columns); const auto & settings = context.getSettingsRef(); Names source_columns_list; source_columns_list.reserve(result.source_columns.size()); for (const auto & type_name : result.source_columns) source_columns_list.emplace_back(type_name.name); if (source_columns_set.size() != source_columns_list.size()) throw Exception("Unexpected duplicates in source columns list.", ErrorCodes::LOGICAL_ERROR); if (select_query) { if (const ASTTablesInSelectQueryElement * node = select_query->join()) { if (settings.enable_optimize_predicate_expression) replaceJoinedTable(node); const auto * joined_expression = node->table_expression->as(); DatabaseAndTableWithAlias table(*joined_expression, context.getCurrentDatabase()); NamesAndTypesList joined_columns = getNamesAndTypeListFromTableExpression(*joined_expression, context); Names original_names = qualifyOccupiedNames(joined_columns, source_columns_set, table); result.analyzed_join.calculateColumnsFromJoinedTable(joined_columns, original_names); } translateQualifiedNames(query, *select_query, context, (storage ? storage->getColumns().ordinary.getNames() : source_columns_list), source_columns_set, result.analyzed_join.columns_from_joined_table); /// Depending on the user's profile, check for the execution rights /// distributed subqueries inside the IN or JOIN sections and process these subqueries. InJoinSubqueriesPreprocessor(context).process(select_query); /// Optimizes logical expressions. LogicalExpressionsOptimizer(select_query, settings.optimize_min_equality_disjunction_chain_length.value).perform(); } /// Creates a dictionary `aliases`: alias -> ASTPtr { LogAST log; QueryAliasesVisitor::Data query_aliases_data{result.aliases}; QueryAliasesVisitor(query_aliases_data, log.stream()).visit(query); } /// Common subexpression elimination. Rewrite rules. { QueryNormalizer::Data normalizer_data(result.aliases, context.getSettingsRef()); QueryNormalizer(normalizer_data).visit(query); } /// Remove unneeded columns according to 'required_result_columns'. /// Leave all selected columns in case of DISTINCT; columns that contain arrayJoin function inside. /// Must be after 'normalizeTree' (after expanding aliases, for aliases not get lost) /// and before 'executeScalarSubqueries', 'analyzeAggregation', etc. to avoid excessive calculations. if (select_query) removeUnneededColumnsFromSelectClause(select_query, required_result_columns); /// Executing scalar subqueries - replacing them with constant values. executeScalarSubqueries(query, context, subquery_depth); /// Optimize if with constant condition after constants was substituted instead of scalar subqueries. OptimizeIfWithConstantConditionVisitor(result.aliases).visit(query); if (select_query) { /// GROUP BY injective function elimination. optimizeGroupBy(select_query, source_columns_set, context); /// Remove duplicate items from ORDER BY. optimizeOrderBy(select_query); /// Remove duplicated elements from LIMIT BY clause. optimizeLimitBy(select_query); /// Remove duplicated columns from USING(...). optimizeUsing(select_query); /// array_join_alias_to_name, array_join_result_to_source. getArrayJoinedColumns(query, result, select_query, source_columns_list, source_columns_set); /// Push the predicate expression down to the subqueries. result.rewrite_subqueries = PredicateExpressionsOptimizer(select_query, settings, context).optimize(); collectJoinedColumns(result.analyzed_join, *select_query, source_columns_set, context.getCurrentDatabase(), settings.join_use_nulls); } return std::make_shared(result); } }