2011-08-28 05:13:24 +00:00
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#include <DB/DataStreams/ExpressionBlockInputStream.h>
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#include <DB/DataStreams/ProjectionBlockInputStream.h>
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#include <DB/DataStreams/FilterBlockInputStream.h>
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#include <DB/DataStreams/LimitBlockInputStream.h>
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2011-09-04 05:14:52 +00:00
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#include <DB/DataStreams/PartialSortingBlockInputStream.h>
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#include <DB/DataStreams/MergeSortingBlockInputStream.h>
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2011-08-28 05:13:24 +00:00
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#include <DB/Parsers/ASTSelectQuery.h>
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#include <DB/Parsers/ASTIdentifier.h>
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2011-09-04 05:14:52 +00:00
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#include <DB/Parsers/ASTFunction.h>
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2011-08-28 08:02:11 +00:00
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#include <DB/Parsers/ASTLiteral.h>
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2011-09-04 05:14:52 +00:00
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#include <DB/Parsers/ASTOrderByElement.h>
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2011-08-28 05:13:24 +00:00
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#include <DB/Interpreters/Expression.h>
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#include <DB/Interpreters/InterpreterSelectQuery.h>
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namespace DB
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{
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InterpreterSelectQuery::InterpreterSelectQuery(ASTPtr query_ptr_, Context & context_, size_t max_block_size_)
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: query_ptr(query_ptr_), context(context_), max_block_size(max_block_size_)
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{
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}
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StoragePtr InterpreterSelectQuery::getTable()
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{
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ASTSelectQuery & query = dynamic_cast<ASTSelectQuery &>(*query_ptr);
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/// Из какой таблицы читать данные. JOIN-ы не поддерживаются.
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String database_name;
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String table_name;
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/** Если таблица не указана - используем таблицу system.one.
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* Если база данных не указана - используем текущую базу данных.
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*/
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if (!query.table)
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{
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database_name = "system";
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table_name = "one";
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}
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else if (!query.database)
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database_name = context.current_database;
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if (query.database)
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database_name = dynamic_cast<ASTIdentifier &>(*query.database).name;
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if (query.table)
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table_name = dynamic_cast<ASTIdentifier &>(*query.table).name;
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if (context.databases->end() == context.databases->find(database_name)
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|| (*context.databases)[database_name].end() == (*context.databases)[database_name].find(table_name))
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throw Exception("Unknown table '" + table_name + "' in database '" + database_name + "'", ErrorCodes::UNKNOWN_TABLE);
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2011-08-28 05:13:24 +00:00
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return (*context.databases)[database_name][table_name];
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}
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DataTypes InterpreterSelectQuery::getReturnTypes()
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{
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context.columns = getTable()->getColumns();
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Expression expression(dynamic_cast<ASTSelectQuery &>(*query_ptr).select_expression_list, context);
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return expression.getReturnTypes();
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}
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BlockInputStreamPtr InterpreterSelectQuery::execute()
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{
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ASTSelectQuery & query = dynamic_cast<ASTSelectQuery &>(*query_ptr);
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StoragePtr table = getTable();
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2011-09-04 05:14:52 +00:00
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2011-08-28 05:13:24 +00:00
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/// Какие столбцы читать из этой таблицы
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context.columns = table->getColumns();
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Poco::SharedPtr<Expression> expression = new Expression(query_ptr, context);
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2011-08-28 08:02:11 +00:00
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Names required_columns = expression->getRequiredColumns();
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/// Если не указан ни один столбец из таблицы, то будем читать первый попавшийся (чтобы хотя бы знать число строк).
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if (required_columns.empty())
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required_columns.push_back(table->getColumns().begin()->first);
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2011-09-04 05:14:52 +00:00
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size_t limit_length = 0;
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size_t limit_offset = 0;
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if (query.limit_length)
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{
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limit_length = boost::get<UInt64>(dynamic_cast<ASTLiteral &>(*query.limit_length).value);
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if (query.limit_offset)
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limit_offset = boost::get<UInt64>(dynamic_cast<ASTLiteral &>(*query.limit_offset).value);
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}
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/** Оптимизация - если не указаны WHERE, GROUP, HAVING, ORDER, но указан LIMIT, и limit + offset < max_block_size,
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* то в качестве размера блока будем использовать limit + offset (чтобы не читать из таблицы больше, чем запрошено).
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*/
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size_t block_size = max_block_size;
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if (!query.where_expression && !query.group_expression_list && !query.having_expression && !query.order_expression_list
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&& query.limit_length && limit_length + limit_offset < block_size)
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{
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block_size = limit_length + limit_offset;
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}
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BlockInputStreamPtr stream = table->read(required_columns, query_ptr, block_size);
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2011-08-28 05:13:24 +00:00
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/// Если есть условие WHERE - сначала выполним часть выражения, необходимую для его вычисления
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if (query.where_expression)
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{
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setPartID(query.where_expression, PART_WHERE);
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stream = new ExpressionBlockInputStream(stream, expression, PART_WHERE);
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stream = new FilterBlockInputStream(stream);
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}
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/// Выполним оставшуюся часть выражения
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setPartID(query.select_expression_list, PART_SELECT);
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if (query.order_expression_list)
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setPartID(query.order_expression_list, PART_ORDER);
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stream = new ExpressionBlockInputStream(stream, expression, PART_SELECT | PART_ORDER);
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stream = new ProjectionBlockInputStream(stream, expression, true, PART_SELECT | PART_ORDER);
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/// Если есть ORDER BY
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if (query.order_expression_list)
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{
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SortDescription order_descr;
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order_descr.reserve(query.order_expression_list->children.size());
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for (ASTs::iterator it = query.order_expression_list->children.begin();
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it != query.order_expression_list->children.end();
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++it)
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{
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ASTPtr elem = (*it)->children.front();
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ASTIdentifier * id_elem = dynamic_cast<ASTIdentifier *>(&*elem);
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ASTFunction * id_func = dynamic_cast<ASTFunction *>(&*elem);
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String name = id_elem ? id_elem->name : elem->getTreeID();
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if (id_func)
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name += "_0";
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order_descr.push_back(SortColumnDescription(name, dynamic_cast<ASTOrderByElement &>(**it).direction));
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}
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stream = new PartialSortingBlockInputStream(stream, order_descr);
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stream = new MergeSortingBlockInputStream(stream, order_descr);
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}
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/// Удалим ненужные больше столбцы
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stream = new ProjectionBlockInputStream(stream, expression, false, PART_SELECT);
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2011-08-28 05:13:24 +00:00
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2011-08-28 08:02:11 +00:00
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/// Если есть LIMIT
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if (query.limit_length)
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{
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stream = new LimitBlockInputStream(stream, limit_length, limit_offset);
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}
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2011-08-28 05:13:24 +00:00
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return stream;
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}
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void InterpreterSelectQuery::setPartID(ASTPtr ast, unsigned part_id)
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{
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ast->part_id |= part_id;
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2011-08-28 05:13:24 +00:00
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for (ASTs::iterator it = ast->children.begin(); it != ast->children.end(); ++it)
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setPartID(*it, part_id);
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}
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}
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