#include "Common/quoteString.h" #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 ILLEGAL_TYPE_OF_ARGUMENT; extern const int UNKNOWN_IDENTIFIER; extern const int NOT_AN_AGGREGATE; extern const int UNEXPECTED_EXPRESSION; extern const int TYPE_MISMATCH; extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH; extern const int INCORRECT_ELEMENT_OF_SET; } static NamesAndTypesList::iterator findColumn(const String & name, NamesAndTypesList & cols) { return std::find_if(cols.begin(), cols.end(), [&](const NamesAndTypesList::value_type & val) { return val.name == name; }); } static size_t getTypeDepth(const DataTypePtr & type) { if (const auto * array_type = typeid_cast(type.get())) return 1 + getTypeDepth(array_type->getNestedType()); else if (const auto * tuple_type = typeid_cast(type.get())) return 1 + (tuple_type->getElements().empty() ? 0 : getTypeDepth(tuple_type->getElements().at(0))); return 0; } template static Block createBlockFromCollection(const Collection & collection, const DataTypes & types, const Context & context) { size_t columns_num = types.size(); MutableColumns columns(columns_num); for (size_t i = 0; i < columns_num; ++i) columns[i] = types[i]->createColumn(); Row tuple_values; for (const auto & value : collection) { if (columns_num == 1) { auto field = convertFieldToType(value, *types[0]); if (!field.isNull() || context.getSettingsRef().transform_null_in) columns[0]->insert(std::move(field)); } else { if (value.getType() != Field::Types::Tuple) throw Exception("Invalid type in set. Expected tuple, got " + String(value.getTypeName()), ErrorCodes::INCORRECT_ELEMENT_OF_SET); const auto & tuple = DB::get(value); size_t tuple_size = tuple.size(); if (tuple_size != columns_num) throw Exception("Incorrect size of tuple in set: " + toString(tuple_size) + " instead of " + toString(columns_num), ErrorCodes::INCORRECT_ELEMENT_OF_SET); if (tuple_values.empty()) tuple_values.resize(tuple_size); size_t i = 0; for (; i < tuple_size; ++i) { tuple_values[i] = convertFieldToType(tuple[i], *types[i]); if (tuple_values[i].isNull() && !context.getSettingsRef().transform_null_in) break; } if (i == tuple_size) for (i = 0; i < tuple_size; ++i) columns[i]->insert(std::move(tuple_values[i])); } } Block res; for (size_t i = 0; i < columns_num; ++i) res.insert(ColumnWithTypeAndName{std::move(columns[i]), types[i], "_" + toString(i)}); return res; } static Field extractValueFromNode(const ASTPtr & node, const IDataType & type, const Context & context) { if (const auto * lit = node->as()) { return convertFieldToType(lit->value, type); } else if (node->as()) { std::pair value_raw = evaluateConstantExpression(node, context); return convertFieldToType(value_raw.first, type, value_raw.second.get()); } else throw Exception("Incorrect element of set. Must be literal or constant expression.", ErrorCodes::INCORRECT_ELEMENT_OF_SET); } static Block createBlockFromAST(const ASTPtr & node, const DataTypes & types, const Context & context) { /// Will form a block with values from the set. Block header; size_t num_columns = types.size(); for (size_t i = 0; i < num_columns; ++i) header.insert(ColumnWithTypeAndName(types[i]->createColumn(), types[i], "_" + toString(i))); MutableColumns columns = header.cloneEmptyColumns(); DataTypePtr tuple_type; Row tuple_values; const auto & list = node->as(); for (const auto & elem : list.children) { if (num_columns == 1) { Field value = extractValueFromNode(elem, *types[0], context); if (!value.isNull() || context.getSettingsRef().transform_null_in) columns[0]->insert(value); } else if (elem->as() || elem->as()) { Field function_result; const Tuple * tuple = nullptr; auto * func = elem->as(); if (func && func->name != "tuple") { if (!tuple_type) tuple_type = std::make_shared(types); function_result = extractValueFromNode(elem, *tuple_type, context); if (function_result.getType() != Field::Types::Tuple) throw Exception("Invalid type of set. Expected tuple, got " + String(function_result.getTypeName()), ErrorCodes::INCORRECT_ELEMENT_OF_SET); tuple = &function_result.get(); } auto * literal = elem->as(); if (literal) { if (literal->value.getType() != Field::Types::Tuple) throw Exception("Invalid type in set. Expected tuple, got " + String(literal->value.getTypeName()), ErrorCodes::INCORRECT_ELEMENT_OF_SET); tuple = &literal->value.get(); } size_t tuple_size = tuple ? tuple->size() : func->arguments->children.size(); if (tuple_size != num_columns) throw Exception("Incorrect size of tuple in set: " + toString(tuple_size) + " instead of " + toString(num_columns), ErrorCodes::INCORRECT_ELEMENT_OF_SET); if (tuple_values.empty()) tuple_values.resize(tuple_size); size_t i = 0; for (; i < tuple_size; ++i) { Field value = tuple ? (*tuple)[i] : extractValueFromNode(func->arguments->children[i], *types[i], context); /// If at least one of the elements of the tuple has an impossible (outside the range of the type) value, then the entire tuple too. if (value.isNull() && !context.getSettings().transform_null_in) break; tuple_values[i] = value; } if (i == tuple_size) for (i = 0; i < tuple_size; ++i) columns[i]->insert(tuple_values[i]); } else throw Exception("Incorrect element of set", ErrorCodes::INCORRECT_ELEMENT_OF_SET); } return header.cloneWithColumns(std::move(columns)); } /** Create a block for set from literal. * 'set_element_types' - types of what are on the left hand side of IN. * 'right_arg' - Literal - Tuple or Array. */ static Block createBlockForSet( const DataTypePtr & left_arg_type, const std::shared_ptr & right_arg, const DataTypes & set_element_types, const Context & context) { auto [right_arg_value, right_arg_type] = evaluateConstantExpression(right_arg, context); const size_t left_type_depth = getTypeDepth(left_arg_type); const size_t right_type_depth = getTypeDepth(right_arg_type); auto throw_unsupported_type = [](const auto & type) { throw Exception("Unsupported value type at the right-side of IN: " + type->getName() + ".", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT); }; Block block; /// 1 in 1; (1, 2) in (1, 2); identity(tuple(tuple(tuple(1)))) in tuple(tuple(tuple(1))); etc. if (left_type_depth == right_type_depth) { Array array{right_arg_value}; block = createBlockFromCollection(array, set_element_types, context); } /// 1 in (1, 2); (1, 2) in ((1, 2), (3, 4)); etc. else if (left_type_depth + 1 == right_type_depth) { auto type_index = right_arg_type->getTypeId(); if (type_index == TypeIndex::Tuple) block = createBlockFromCollection(DB::get(right_arg_value), set_element_types, context); else if (type_index == TypeIndex::Array) block = createBlockFromCollection(DB::get(right_arg_value), set_element_types, context); else throw_unsupported_type(right_arg_type); } else throw_unsupported_type(right_arg_type); return block; } /** Create a block for set from expression. * 'set_element_types' - types of what are on the left hand side of IN. * 'right_arg' - list of values: 1, 2, 3 or list of tuples: (1, 2), (3, 4), (5, 6). * * We need special implementation for common AST, because in case, when we interpret tuple or array * as function, `evaluateConstantExpression` works extremely slow. */ static Block createBlockForSet( const DataTypePtr & left_arg_type, const ASTPtr & right_arg, const DataTypes & set_element_types, const Context & context) { auto get_tuple_type_from_ast = [&context](const ASTPtr & tuple_ast) -> DataTypePtr { const auto * func = tuple_ast->as(); if (func && (func->name == "tuple" || func->name == "array") && !func->arguments->children.empty()) { /// Won't parse all values of outer tuple. auto element = func->arguments->children.at(0); std::pair value_raw = evaluateConstantExpression(element, context); return std::make_shared(DataTypes({value_raw.second})); } return evaluateConstantExpression(tuple_ast, context).second; }; const DataTypePtr & right_arg_type = get_tuple_type_from_ast(right_arg); size_t left_tuple_depth = getTypeDepth(left_arg_type); size_t right_tuple_depth = getTypeDepth(right_arg_type); ASTPtr elements_ast; /// 1 in 1; (1, 2) in (1, 2); identity(tuple(tuple(tuple(1)))) in tuple(tuple(tuple(1))); etc. if (left_tuple_depth == right_tuple_depth) { ASTPtr exp_list = std::make_shared(); exp_list->children.push_back(right_arg); elements_ast = exp_list; } /// 1 in (1, 2); (1, 2) in ((1, 2), (3, 4)); etc. else if (left_tuple_depth + 1 == right_tuple_depth) { const auto * set_func = right_arg->as(); if (!set_func || (set_func->name != "tuple" && set_func->name != "array")) throw Exception("Incorrect type of 2nd argument for function 'in'" ". Must be subquery or set of elements with type " + left_arg_type->getName() + ".", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT); elements_ast = set_func->arguments; } else throw Exception("Invalid types for IN function: " + left_arg_type->getName() + " and " + right_arg_type->getName() + ".", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT); return createBlockFromAST(elements_ast, set_element_types, context); } SetPtr makeExplicitSet( const ASTFunction * node, const Block & sample_block, bool create_ordered_set, const Context & context, const SizeLimits & size_limits, PreparedSets & prepared_sets) { const IAST & args = *node->arguments; if (args.children.size() != 2) throw Exception("Wrong number of arguments passed to function in", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH); const ASTPtr & left_arg = args.children.at(0); const ASTPtr & right_arg = args.children.at(1); const DataTypePtr & left_arg_type = sample_block.getByName(left_arg->getColumnName()).type; DataTypes set_element_types = {left_arg_type}; const auto * left_tuple_type = typeid_cast(left_arg_type.get()); if (left_tuple_type && left_tuple_type->getElements().size() != 1) set_element_types = left_tuple_type->getElements(); for (auto & element_type : set_element_types) if (const auto * low_cardinality_type = typeid_cast(element_type.get())) element_type = low_cardinality_type->getDictionaryType(); auto set_key = PreparedSetKey::forLiteral(*right_arg, set_element_types); if (prepared_sets.count(set_key)) return prepared_sets.at(set_key); /// Already prepared. Block block; if (const auto & right_arg_literal = std::dynamic_pointer_cast(right_arg)) block = createBlockForSet(left_arg_type, right_arg_literal, set_element_types, context); else block = createBlockForSet(left_arg_type, right_arg, set_element_types, context); SetPtr set = std::make_shared(size_limits, create_ordered_set, context.getSettingsRef().transform_null_in); set->setHeader(block.cloneEmpty()); set->insertFromBlock(block); set->finishInsert(); prepared_sets[set_key] = set; return set; } ScopeStack::ScopeStack(const ExpressionActionsPtr & actions, const Context & context_) : context(context_) { stack.emplace_back(); stack.back().actions = actions; const Block & sample_block = actions->getSampleBlock(); for (size_t i = 0, size = sample_block.columns(); i < size; ++i) stack.back().new_columns.insert(sample_block.getByPosition(i).name); } void ScopeStack::pushLevel(const NamesAndTypesList & input_columns) { stack.emplace_back(); Level & prev = stack[stack.size() - 2]; ColumnsWithTypeAndName all_columns; NameSet new_names; for (const auto & input_column : input_columns) { all_columns.emplace_back(nullptr, input_column.type, input_column.name); new_names.insert(input_column.name); stack.back().new_columns.insert(input_column.name); } const Block & prev_sample_block = prev.actions->getSampleBlock(); for (size_t i = 0, size = prev_sample_block.columns(); i < size; ++i) { const ColumnWithTypeAndName & col = prev_sample_block.getByPosition(i); if (!new_names.count(col.name)) all_columns.push_back(col); } stack.back().actions = std::make_shared(all_columns, context); } size_t ScopeStack::getColumnLevel(const std::string & name) { for (int i = static_cast(stack.size()) - 1; i >= 0; --i) if (stack[i].new_columns.count(name)) return i; throw Exception("Unknown identifier: " + name, ErrorCodes::UNKNOWN_IDENTIFIER); } void ScopeStack::addAction(const ExpressionAction & action) { size_t level = 0; Names required = action.getNeededColumns(); for (const auto & elem : required) level = std::max(level, getColumnLevel(elem)); Names added; stack[level].actions->add(action, added); stack[level].new_columns.insert(added.begin(), added.end()); for (const auto & elem : added) { const ColumnWithTypeAndName & col = stack[level].actions->getSampleBlock().getByName(elem); for (size_t j = level + 1; j < stack.size(); ++j) stack[j].actions->addInput(col); } } ExpressionActionsPtr ScopeStack::popLevel() { ExpressionActionsPtr res = stack.back().actions; stack.pop_back(); return res; } const Block & ScopeStack::getSampleBlock() const { return stack.back().actions->getSampleBlock(); } struct CachedColumnName { String cached; const String & get(const ASTPtr & ast) { if (cached.empty()) cached = ast->getColumnName(); return cached; } }; bool ActionsMatcher::needChildVisit(const ASTPtr & node, const ASTPtr & child) { /// Visit children themself if (node->as() || node->as() || node->as()) return false; /// Do not go to FROM, JOIN, UNION. if (child->as() || child->as()) return false; return true; } void ActionsMatcher::visit(const ASTPtr & ast, Data & data) { if (const auto * identifier = ast->as()) visit(*identifier, ast, data); else if (const auto * node = ast->as()) visit(*node, ast, data); else if (const auto * literal = ast->as()) visit(*literal, ast, data); } void ActionsMatcher::visit(const ASTIdentifier & identifier, const ASTPtr & ast, Data & data) { CachedColumnName column_name; if (data.hasColumn(column_name.get(ast))) return; if (!data.only_consts) { /// The requested column is not in the block. /// If such a column exists in the table, then the user probably forgot to surround it with an aggregate function or add it to GROUP BY. bool found = false; for (const auto & column_name_type : data.source_columns) if (column_name_type.name == column_name.get(ast)) found = true; if (found) throw Exception("Column " + backQuote(column_name.get(ast)) + " is not under aggregate function and not in GROUP BY", ErrorCodes::NOT_AN_AGGREGATE); /// Special check for WITH statement alias. Add alias action to be able to use this alias. if (identifier.prefer_alias_to_column_name && !identifier.alias.empty()) data.addAction(ExpressionAction::addAliases({{identifier.name, identifier.alias}})); } } void ActionsMatcher::visit(const ASTFunction & node, const ASTPtr & ast, Data & data) { CachedColumnName column_name; if (data.hasColumn(column_name.get(ast))) return; if (node.name == "lambda") throw Exception("Unexpected lambda expression", ErrorCodes::UNEXPECTED_EXPRESSION); /// Function arrayJoin. if (node.name == "arrayJoin") { if (node.arguments->children.size() != 1) throw Exception("arrayJoin requires exactly 1 argument", ErrorCodes::TYPE_MISMATCH); ASTPtr arg = node.arguments->children.at(0); visit(arg, data); if (!data.only_consts) { String result_name = column_name.get(ast); data.addAction(ExpressionAction::copyColumn(arg->getColumnName(), result_name)); NameSet joined_columns; joined_columns.insert(result_name); data.addAction(ExpressionAction::arrayJoin(joined_columns, false, data.context)); } return; } SetPtr prepared_set; if (checkFunctionIsInOrGlobalInOperator(node)) { /// Let's find the type of the first argument (then getActionsImpl will be called again and will not affect anything). visit(node.arguments->children.at(0), data); if (!data.no_makeset && (prepared_set = makeSet(node, data, data.no_subqueries))) { /// Transform tuple or subquery into a set. } else { if (!data.only_consts) { /// We are in the part of the tree that we are not going to compute. You just need to define types. /// Do not subquery and create sets. We replace "in*" function to "in*IgnoreSet". auto argument_name = node.arguments->children.at(0)->getColumnName(); data.addAction(ExpressionAction::applyFunction( FunctionFactory::instance().get(node.name + "IgnoreSet", data.context), { argument_name, argument_name }, column_name.get(ast))); } return; } } if (AggregateFunctionFactory::instance().isAggregateFunctionName(node.name)) return; /// Context object that we pass to function should live during query. const Context & function_context = data.context.hasQueryContext() ? data.context.getQueryContext() : data.context; FunctionOverloadResolverPtr function_builder; try { function_builder = FunctionFactory::instance().get(node.name, function_context); } catch (DB::Exception & e) { auto hints = AggregateFunctionFactory::instance().getHints(node.name); if (!hints.empty()) e.addMessage("Or unknown aggregate function " + node.name + ". Maybe you meant: " + toString(hints)); e.rethrow(); } Names argument_names; DataTypes argument_types; bool arguments_present = true; /// If the function has an argument-lambda expression, you need to determine its type before the recursive call. bool has_lambda_arguments = false; for (size_t arg = 0; arg < node.arguments->children.size(); ++arg) { auto & child = node.arguments->children[arg]; const auto * lambda = child->as(); const auto * identifier = child->as(); if (lambda && lambda->name == "lambda") { /// If the argument is a lambda expression, just remember its approximate type. if (lambda->arguments->children.size() != 2) throw Exception("lambda requires two arguments", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH); const auto * lambda_args_tuple = lambda->arguments->children.at(0)->as(); if (!lambda_args_tuple || lambda_args_tuple->name != "tuple") throw Exception("First argument of lambda must be a tuple", ErrorCodes::TYPE_MISMATCH); has_lambda_arguments = true; argument_types.emplace_back(std::make_shared(DataTypes(lambda_args_tuple->arguments->children.size()))); /// Select the name in the next cycle. argument_names.emplace_back(); } else if (checkFunctionIsInOrGlobalInOperator(node) && arg == 1 && prepared_set) { ColumnWithTypeAndName column; column.type = std::make_shared(); /// If the argument is a set given by an enumeration of values (so, the set was already built), give it a unique name, /// so that sets with the same literal representation do not fuse together (they can have different types). if (!prepared_set->empty()) column.name = data.getUniqueName("__set"); else column.name = child->getColumnName(); if (!data.hasColumn(column.name)) { auto column_set = ColumnSet::create(1, prepared_set); /// If prepared_set is not empty, we have a set made with literals. /// Create a const ColumnSet to make constant folding work if (!prepared_set->empty()) column.column = ColumnConst::create(std::move(column_set), 1); else column.column = std::move(column_set); data.addAction(ExpressionAction::addColumn(column)); } argument_types.push_back(column.type); argument_names.push_back(column.name); } else if (identifier && (functionIsJoinGet(node.name) || functionIsDictGet(node.name)) && arg == 0) { auto table_id = IdentifierSemantic::extractDatabaseAndTable(*identifier); table_id = data.context.resolveStorageID(table_id, Context::ResolveOrdinary); auto column_string = ColumnString::create(); column_string->insert(table_id.getDatabaseName() + "." + table_id.getTableName()); ColumnWithTypeAndName column( ColumnConst::create(std::move(column_string), 1), std::make_shared(), data.getUniqueName("__" + node.name)); data.addAction(ExpressionAction::addColumn(column)); argument_types.push_back(column.type); argument_names.push_back(column.name); } else { /// If the argument is not a lambda expression, call it recursively and find out its type. visit(child, data); // In the above visit() call, if the argument is a literal, we // generated a unique column name for it. Use it instead of a generic // display name. auto child_column_name = child->getColumnName(); const auto * as_literal = child->as(); if (as_literal) { assert(!as_literal->unique_column_name.empty()); child_column_name = as_literal->unique_column_name; } if (data.hasColumn(child_column_name)) { argument_types.push_back(data.getSampleBlock().getByName(child_column_name).type); argument_names.push_back(child_column_name); } else { if (data.only_consts) arguments_present = false; else throw Exception("Unknown identifier: " + child_column_name + " there are columns: " + data.getSampleBlock().dumpNames(), ErrorCodes::UNKNOWN_IDENTIFIER); } } } if (data.only_consts && !arguments_present) return; if (has_lambda_arguments && !data.only_consts) { function_builder->getLambdaArgumentTypes(argument_types); /// Call recursively for lambda expressions. for (size_t i = 0; i < node.arguments->children.size(); ++i) { ASTPtr child = node.arguments->children[i]; const auto * lambda = child->as(); if (lambda && lambda->name == "lambda") { const DataTypeFunction * lambda_type = typeid_cast(argument_types[i].get()); const auto * lambda_args_tuple = lambda->arguments->children.at(0)->as(); const ASTs & lambda_arg_asts = lambda_args_tuple->arguments->children; NamesAndTypesList lambda_arguments; for (size_t j = 0; j < lambda_arg_asts.size(); ++j) { auto opt_arg_name = tryGetIdentifierName(lambda_arg_asts[j]); if (!opt_arg_name) throw Exception("lambda argument declarations must be identifiers", ErrorCodes::TYPE_MISMATCH); lambda_arguments.emplace_back(*opt_arg_name, lambda_type->getArgumentTypes()[j]); } data.actions_stack.pushLevel(lambda_arguments); visit(lambda->arguments->children.at(1), data); ExpressionActionsPtr lambda_actions = data.actions_stack.popLevel(); String result_name = lambda->arguments->children.at(1)->getColumnName(); lambda_actions->finalize(Names(1, result_name)); DataTypePtr result_type = lambda_actions->getSampleBlock().getByName(result_name).type; Names captured; Names required = lambda_actions->getRequiredColumns(); for (const auto & required_arg : required) if (findColumn(required_arg, lambda_arguments) == lambda_arguments.end()) captured.push_back(required_arg); /// We can not name `getColumnName()`, /// because it does not uniquely define the expression (the types of arguments can be different). String lambda_name = data.getUniqueName("__lambda"); auto function_capture = std::make_unique( lambda_actions, captured, lambda_arguments, result_type, result_name); auto function_capture_adapter = std::make_shared(std::move(function_capture)); data.addAction(ExpressionAction::applyFunction(function_capture_adapter, captured, lambda_name)); argument_types[i] = std::make_shared(lambda_type->getArgumentTypes(), result_type); argument_names[i] = lambda_name; } } } if (data.only_consts) { for (const auto & argument_name : argument_names) { if (!data.hasColumn(argument_name)) { arguments_present = false; break; } } } if (arguments_present) { data.addAction(ExpressionAction::applyFunction(function_builder, argument_names, column_name.get(ast))); } } void ActionsMatcher::visit(const ASTLiteral & literal, const ASTPtr & /* ast */, Data & data) { DataTypePtr type = applyVisitor(FieldToDataType(), literal.value); const auto value = convertFieldToType(literal.value, *type); // FIXME why do we have a second pass with a clean sample block over the same // AST here? Anyway, do not modify the column name if it is set already. if (literal.unique_column_name.empty()) { const auto default_name = literal.getColumnName(); const auto & block = data.getSampleBlock(); const auto * existing_column = block.findByName(default_name); /* * To approximate CSE, bind all identical literals to a single temporary * columns. We try to find the column by its default name, but after that * we have to check that it contains the correct data. This might not be * the case if it is a user-supplied column, or it is from under a join, * etc. * Overall, this is a hack around a generally poor name-based notion of * column identity we currently use. */ if (existing_column && existing_column->column && isColumnConst(*existing_column->column) && existing_column->column->size() == 1 && existing_column->column->operator[](0) == value) { const_cast(literal).unique_column_name = default_name; } else { const_cast(literal).unique_column_name = data.getUniqueName(default_name); } } if (data.hasColumn(literal.unique_column_name)) { return; } ColumnWithTypeAndName column; column.name = literal.unique_column_name; column.column = type->createColumnConst(1, value); column.type = type; data.addAction(ExpressionAction::addColumn(column)); } SetPtr ActionsMatcher::makeSet(const ASTFunction & node, Data & data, bool no_subqueries) { /** You need to convert the right argument to a set. * This can be a table name, a value, a value enumeration, or a subquery. * The enumeration of values is parsed as a function `tuple`. */ const IAST & args = *node.arguments; const ASTPtr & left_in_operand = args.children.at(0); const ASTPtr & right_in_operand = args.children.at(1); const Block & sample_block = data.getSampleBlock(); /// If the subquery or table name for SELECT. const auto * identifier = right_in_operand->as(); if (right_in_operand->as() || identifier) { if (no_subqueries) return {}; auto set_key = PreparedSetKey::forSubquery(*right_in_operand); if (data.prepared_sets.count(set_key)) return data.prepared_sets.at(set_key); /// A special case is if the name of the table is specified on the right side of the IN statement, /// and the table has the type Set (a previously prepared set). if (identifier) { auto table_id = data.context.resolveStorageID(right_in_operand); StoragePtr table = DatabaseCatalog::instance().tryGetTable(table_id, data.context); if (table) { StorageSet * storage_set = dynamic_cast(table.get()); if (storage_set) { data.prepared_sets[set_key] = storage_set->getSet(); return storage_set->getSet(); } } } /// We get the stream of blocks for the subquery. Create Set and put it in place of the subquery. String set_id = right_in_operand->getColumnName(); SubqueryForSet & subquery_for_set = data.subqueries_for_sets[set_id]; /// If you already created a Set with the same subquery / table. if (subquery_for_set.set) { data.prepared_sets[set_key] = subquery_for_set.set; return subquery_for_set.set; } SetPtr set = std::make_shared(data.set_size_limit, false, data.context.getSettingsRef().transform_null_in); /** The following happens for GLOBAL INs: * - in the addExternalStorage function, the IN (SELECT ...) subquery is replaced with IN _data1, * in the subquery_for_set object, this subquery is set as source and the temporary table _data1 as the table. * - this function shows the expression IN_data1. */ if (!subquery_for_set.source && data.no_storage_or_local) { auto interpreter = interpretSubquery(right_in_operand, data.context, data.subquery_depth, {}); subquery_for_set.source = std::make_shared( interpreter->getSampleBlock(), [interpreter]() mutable { return interpreter->execute().getInputStream(); }); /** Why is LazyBlockInputStream used? * * The fact is that when processing a query of the form * SELECT ... FROM remote_test WHERE column GLOBAL IN (subquery), * if the distributed remote_test table contains localhost as one of the servers, * the query will be interpreted locally again (and not sent over TCP, as in the case of a remote server). * * The query execution pipeline will be: * CreatingSets * subquery execution, filling the temporary table with _data1 (1) * CreatingSets * reading from the table _data1, creating the set (2) * read from the table subordinate to remote_test. * * (The second part of the pipeline under CreateSets is a reinterpretation of the query inside StorageDistributed, * the query differs in that the database name and tables are replaced with subordinates, and the subquery is replaced with _data1.) * * But when creating the pipeline, when creating the source (2), it will be found that the _data1 table is empty * (because the query has not started yet), and empty source will be returned as the source. * And then, when the query is executed, an empty set will be created in step (2). * * Therefore, we make the initialization of step (2) lazy * - so that it does not occur until step (1) is completed, on which the table will be populated. * * Note: this solution is not very good, you need to think better. */ } subquery_for_set.set = set; data.prepared_sets[set_key] = set; return set; } else { if (sample_block.has(left_in_operand->getColumnName())) /// An explicit enumeration of values in parentheses. return makeExplicitSet(&node, sample_block, false, data.context, data.set_size_limit, data.prepared_sets); else return {}; } } }