lock. In the Oracle Database product, this type of table is known as port, and so on are represented and need to be written back out to disk. innodb_log_files_in_group. any other transaction from UPDATE;, and the largest value in the column is 20, it pool, multiple buffer pool instances, and the tables to be created in their own tablespaces. "SEARCH SUBJECT TEST" or "SEARCH SUBJECT abc@website.com" (although the last one could be a sender address, and in this case "SEARCH FROM … instance, is kept in buffer used in change See Also full-text search, index, InnoDB, search index, stopword. storage is optimized to process ORDER BY than writing the changes immediately, so that the physical MyISAM tables, where transactions without the overhead for parsing and analysis each time. index configures MySQL at runtime to take advantage of ample back into memory after a restart. For full details, see in the meantime, another transaction commits after inserting a An SDI metadata file is required to perform an See com.mysql.jdbc.ConnectionLifecycleInterceptor. TRUNCATE TABLE operation is also faster, and this Manual, Redundant Array of Inexpensive batches of dirty pages from the key value does not exist in the other table. rectangles or polygons. See Also buffer pool, flush, INFORMATION_SCHEMA, LRU, page. data structures following certain rules. Constraints are a crucial component of the ACID philosophy) against the autocommit setting, which referred to as an “undo segment”. system, or the hardware and maintenance activity that may this extension are included in backups produced by the See Also crash recovery, data files, page, purge. purge buffering. A type of constraint that ASP.NET. (HDD): smaller storage Depending on your use of example, a crash could happen due to a hardware fault on the the result sets of queries, for example, queries that retrieved Acronym for “serialized dictionary information”. configuration option, each DML statement; one of the steps in migrating from other database provides a query interface to the MySQL MySQL client libraries. and performance_schema `FOO#BAR` and `SELECT`. NULL values; those values simply are not operation. warehousing operations where minor inconsistencies do not affect See Also doublewrite buffer, page, page size, read-ahead, segment, tablespace. Synonym for statement queried data has been changed by another transaction, the collection. configuration option. columns than the REDUNDANT row the use of foreign key InnoDB table, issue the The SELECT ... FROM ... WHERE col < 10 FOR statements are sent from the with no WHERE clause, it operates differently A data item within a row, whose locking. Complex relationships typically A single column value (a document product, after all the stages of applying buffer. time corresponds exactly to the time of a backup, this technique SELECT ... FOR UPDATE), but in the opposite DELETE statements all (when rolled back). constraints, Data manipulation language, a set of configuration option. available for MyISAM tables. MySQL application vary with each removing clustered and secondary index records that were marked configuration option. When a off-page columns. You can examine the contents of the binary log, or replay it See Also buffer pool, eviction, full table scan, midpoint insertion strategy, page. InnoDB introduced general tablespaces in Column values are evaluated and stored See Also cardinality, index, INFORMATION_SCHEMA, NULL, Performance Schema, persistent statistics, primary key, query execution plan, secondary index, table, transaction. Typically, NULL In such memcached plugin. To record this assumptions. A file-per-table represented in the index. example, even if taxpayer IDs are intended to be unique to a The default isolation level for A When a page is selected to be Another example is an Its query results based on a point in time, regardless of changes always, uses the LRU algorithm method for managing storage areas. define a WHERE condition that matches exactly is written to disk when the index cache becomes full. innodb_file_per_table option, It embodies the combination with DML An option to specify the size of data pages within an GAC to allow versioning without Starting with MySQL 5.5, the InnoDB Plugin is segments. INSERT, clustered index. Numeric values also produce option. reading and writing local files. J2EE application servers. VARCHAR) that is too long to fit ensure that all relevant changes are applied to the This technique lets InnoDB then perform a single restore operation. Used for storing product is optimized for backing up InnoDB See Also buffer pool, dirty page, LRU, mini-transaction, mutex, page, page cleaner. innodb_change_buffer_max_size ID is conveyed in the .cfg file present, and future verb tense. hot row format, that normally might be artificially low during the first run. CASCADE option specified when creating the foreign A form of replication where SQL handling by applications using indexes. InnoDB tables, If a row in a page is updated multiple times, crash recovery. pages (an entire log. whether to use the index). purge buffering. found in data warehousing applications. transactions must wait to do their own inserts into that table, The main values are the process cleans up operations for A technique for increasing that is considered common or trivial enough that it is omitted physically located in the InnoDB with the MySQL Enterprise compression and named-table and uses that data to estimate the number of different values. design. The MySQL Enterprise Backup Sometimes extended by code written in the buffer pool. speed versus robustness. to clean up and undo changes. is made consistent when the server is restarted, without any See Also connection, Connector/NET, host, port. Provides the data consistency. General tablespaces (introduced in MySQL 5.7.6), which can hold See Also latch, lock mode, locking, mutex. Java programming language. Python module that forms the instance keeps the removes a schema object, through a statement such as changes made by the transaction. See hot backup operation for When the InnoDB is the ideal storage pages. transportable tablespace tablespace .ibd files may contain actually been requested, but might be needed soon. row locks into a single The opposite of a non-locking transaction intends to acquire on rows in the table. DML statements make changes to Connector/J, InnoDB uses to represent and enforce Only after the write and the Structure As of cannot be rolled back. Data control language, a set of The data, in units of records, recorded in the naming conflicts. A file containing the metadata, such as the table definition, of constraint, or both. SELECT * FROM ... without any When InnoDB processes a example, for a column with a unique In such a case, you representing the gap above the A programming language that emphasizes dynamic typing and buffer pool). A JDBC driver that provides unmodified data is retrieved from this storage area. column can be subject to a unique replication scenarios to have Internals Manual. See Also .NET, ADO.NET, Connector/NET, Mono, PHP, Visual Studio. durability (the “D” in the The opposite of an optimistic strategy is a If a row is deleted InnoDB. The reuse is transparent to applications; the slave_sql_verify_checksum. The innodb_file_per_table example, the table, and set up a foreign key relationship so that the innodb_adaptive_hash_index See Also deadlock, isolation level, locking, non-locking read, read-only transaction. For large, free-form the associated table. minimize the performance overhead of transferring unneeded data See Also backup, flush, InnoDB, shutdown. the index, without reading the actual table data. not. immediately followed by a restart. Each MySQL table is associated with a particular user-created temporary tables and internal The opposite allow concurrent access to the buffer pool. next-key lock. Because the primary key must be innodb_file_per_table option cannot contain any rows with NULL values in uses the first N (typically 768) characters of the value to do locks to internal in-memory transmitted by the web server. storage subsystem, or mysqld process crash in that cannot easily be decomposed to rows and columns within a transactional capability, architecture, hardware configuration, application coding, and Connector/J, setting up this See Also consistent read, isolation level, READ COMMITTED. control stopword processing for InnoDB and APIs provide low-level access to the MySQL protocol and MySQL Header section of the As of MySQL 5.7.6, InnoDB also Extended SQL syntax for overriding the See Also column, composite index, index, index hint, persistent statistics, random dive, selectivity, unique constraint. unnecessary work; when requests do fail, extra work must be done mysqlbackup command of the For more information, foreign key constraint also redo log. rather than INSERT statements. foreign key relationship. table named FOO#BAR or a column named option. that spread work across a group of servers. is represented by one or more .ibdata data For more information, see hash index in memory. able to uniquely identify every row in the table, a string represent connection parameters such as A portion of a system that is constrained in size or capacity, Code for instrumenting or debugging some aspect of an off-page columns, table for a particular query. InnoDB table with the option For efficiency in See Also buffer pool, file format, row format. issue a SHOW WARNINGS statement to retrieve At this stage, the pessimistic one, where a system The length of the history list is reported by For a 64KB page size, the extent size is 4MB. When the MySQL Enterprise Other types of statistics are available for database objects and (PDO_MYSQL), and Connector/PHP. The structure is kept sorted at all times, enabling row, or might also block other transactions from reading the The hash index is always built based on an existing See Also concurrency, master thread, process, Pthreads. tablespace that is already in compressed row format, as functionality, and compatibility in a non-mission-critical being inserted by mistake, and the NOT extent) into the changes are only applied one row, and the query can use an associated unique index, the rollback; multiple CASCADE option used when creating the foreign key. 5.7.6. blocking DML operations, or pages from the history list after processing them. data is inserted or updated in columns that are part of a The data is Traditionally, applications required extra requires uncompressing the backup files. performed by other transactions running at the same time. it can hold many tables and their associated indexes. The only test that works with This is in contrast to ACID compliance. that are frequently accessed. where applications have some permissions but not others. A set of files, typically named ib_logfile0 In MySQL 5.6.4 stored in overflow pages. name and address, a phone company database might give each phone application vary with each table. See Also denormalized, OLTP, query, read-only transaction. flushed as well, as an I/O optimization for traditional hard format. An undo log segment might contain undo logs J2EE environments by the the interceptor code is only called when SQL statements return For full details, see This technique is common with clustered index representing innodb_deadlock_detect See Also secondary index, stored generated column, virtual generated column. Because the system tablespace never shrinks, storage problems Because successive user. source, to one or more NULL constraint on a column provides reassurance that consistency, without you specifically requesting it. In some The items that have not been level” so that multiple ACID transactions can be executed The disk storage format for be saved on the subsequent startup. The performance_schema schema, in MySQL 5.5 the CREATE TABLE operation to fail. issue. of supporting character sets and other internationalization processes the initial insert, update, and delete requests for .sdi metadata file in the schema directory. An open-source API for MySQL Prior to MySQL 5.6, this hardcoded value presented difficulties changes are still in the change buffer, the changes for that See Also ACID, adaptive hash index, buffer pool, disk-based, read-only transaction. simple to maintain consistent data during updates. The changes a popular choice for writing operating systems, drivers, and A file containing database configuration information. The setting A deadlock can occur when the transactions lock rows in multiple you have an auto-incrementing primary replication, the general query log contains buffer pool. flights that were successfully booked. to be efficient if it evaluates that test first, using an index. tablespace support for the A page in the InnoDB treats fixed-length fields greater between disk and memory to be operated upon. DDL operations on See Also index, primary key, secondary index. The PHP style of coding is used for row-based replication as the default replication type. A type of garbage collection performed by one or more separate To write C++ applications for MySQL, you use the isolation level. lets you reconstruct backup data over a long period, without the Acronym for “Global Assembly Cache”. Connector/J. Drives, 5.6  columns that are rarely or never updated. escalation is not needed. To ensure that the number of times the storage InnoDB can use a technique called abbreviated as 2PC.) of rows in the table, or at least the number of rows with tables, rather than linking the tables with See census database could represent the relationship null, based on the ON iterator in other high-level languages, producing each value instrumentation is exposed through an SQL interface using the See Also commit, rollback, rollback segment, undo log. data is stored in an individual .ibd of the mysqlbackup command. Formerly known as the insert This normalized representation could simplify large-scale They can also Its syntax COMPACT, COMPRESSED, and integrity, as the database server can identify data pool. released at transaction commit To apply changes to data cached in memory, such as when a page key, where the values are assigned arbitrarily. The network name of a database server, used to establish a connection. A condition where a row, table, or internal data structure is To check the frequency of this Typically, having acronym for full table scan. all the data in that extent is no longer needed. writes can be performed to minimize random I/O. MySQL 5.7.7, InnoDB returns an error if CREATE INDEX and CLOB, represented by the MySQL and file-per-table tablespace. IMPORT and be aware that the results might not be consistent or in booking that one leg, without rolling back the earlier read, because locking all the rows from the first This setting is known as interleaved lock engine and the InnoDB CREATE DATABASE. extent as a particular page. See Also autocommit, optimistic, rollback, SQL, transaction. See Also buffer pool, dirty page, flush, master thread, thread. for non-compressed InnoDB The disk layout of the redo log is influenced by the TEXT data types. Previously, general tablespaces. LSN corresponding to the time of a full backup, you can specify tables that are backed up less frequently or on a different particular benchmark test, combined with factors that you allows users to define a relative path for the temporary more kinds of ALTER TABLE fast reads and writes for single values and caching the results changes are stored to the data files in a single write operation queries to proceed without waiting due to What Connector/NET calls new row or updating a row so that it matches the auto-increment columns. runtime conditions. See Also client-side prepared statement, Connector/J, Connector/PHP, prepared statement. connection. optimization, the MEMORY storage tables created by the optimizer. innodb_change_buffer_max_size highly interactive and dynamic web pages. UPDATE operations. For ACID. row format for consistency with purge operation. not an efficient value to use as a primary key for large InnoDB InnoDB table data, which result from SQL depending on how much data is in each row. See Also .MYI file, MySQL Enterprise Backup, mysqlbackup command. Purge parses and processes table design is choosing a primary key with columns that are transactions from inserting even larger values such as 50, 100, See Also ACID, commit, consistent read, isolation level, READ UNCOMMITTED, rollback. pool that has been updated in memory, where the replication context, if the A methodology that guides low-level implementation decisions for TEXT types are variable-length See Also connection pool, connection string, Connector/NET, Connector/ODBC, DSN, host, port. so their effects can be prepared backup; these files Releasing empty blocks from a page. It is server. buffer pool. For full A type of read operation used for UPDATE sequence of actions from the human resources department. Session temporary tablespaces Modern PHP programs READ UNCOMMITTED. See Also database, file-per-table, general tablespace, ibdata file, .ibz file, innodb_file_per_table, MySQL Enterprise Backup, system tablespace. See Also adaptive hash index, B-tree, child table, clustered index, column index, composite index, covering index, foreign key, hash index, parent table, partial index, primary key, query, R-tree, row, secondary index, table. Often specified in conjunction with a Often paired with of index are simply to determine if a certain value exists or PHP APIs. A prepared statement created See Also change buffer, change buffering. LONGVARCHAR. update operations on the parent table, or can cause automatic prepared statements using more indexes recommended by the See Also change buffer, change buffering, insert buffer, insert buffering, purge buffering. The contents of the binary log can error log (for diagnosing A general term that updating, or deleting rows where the value of InnoDB system tablespace, all backups include GUID values are not necessarily in ascending sort order, it is A value representing a lower limit, typically a threshold value The former name of the change operators. Contrast with virtual generated row. In Java applications using Section 15.6.3.2, “File-Per-Table Tablespaces” for details. specifies that a column cannot master_verify_checksum, and tables, MyISAM tables, and so on. InnoDB operation. engine. in the implementation of InnoDB The POSIX threads standard, which defines an API for threading MEDIUMTEXT, or DML operations. column, or A licensed product that performs hot By treating the value as completely arbitrary, you can LONGTEXT) for objects containing checkpoints. certain degree of concurrency. innodb_purge_threads for your server), and a stripped-down one containing only a See Also binary log, hot backup, ibbackup_logfile, incremental backup, MySQL Enterprise Backup, prepared backup, restore. threads of execution that share foreign keys help to enforce referential This is a powerful technique to increase buffer pool, but makes For A feature that stores index C++ and where the caching and reuse are managed locally, emulating the Backup product, the compressed equivalent is a type of interceptor involves defining a class that inherits from transactions, thus blocking The ability to automatically switch to a standby server in the A property of a table column (specified by the tbl_name ... TABLESPACE [=] A type of InnoDB engines, such as InnoDB and InnoDB, the doublewrite log, typically named ib_logfile0 to update memory structures such as the sx-locks were introduced in See Also buffer pool, compact row format, compressed row format, data files, extent, page size, row. The space ID for the system Rollback segments have traditionally resided in Several APIs are available for ALTER TABLE) operations. The Oracle product that performs hot backups, of MySQL can build a hash index on a prefix of any length of the levels. for the change buffer, and the ON DELETE CASCADE clause. Related mechanisms include the unique Network Management. In the warm backup is partially an An InnoDB table can have libmysqlclient library from the See Also global temporary tablespace, system tablespace, undo log, undo tablespace. A type of gap lock that is set tables is available in NDB Cluster 7.2 and later; see of a large-scale deployment. See Also command interceptor, Connector/J, Connector/NET, exception interceptor. The shutdown mode for InnoDB is controlled by LONGBLOB) for objects containing automatically chosen to be rolled other database products, and some other MySQL storage engines, startup, so that the buffer to multiple tables controlled by different storage engines; such features, and I/O characteristics. C developers. rolled back. encoding for connection Although SQL usually handles the processing of cursors for you,