See Also full-text search, FULLTEXT index.  Index condition pushdown (ICP) is an optimization that pushes part of a  WHERE  condition down to the storage engine if parts of the condition can be evaluated using fields from the  index . ICP can reduce the number of times the  storage engine  must access the base table and the number of times the MySQL server must access the storage engine. For more information, see Section 8.2.1.6, “Index Condition Pushdown Optimization” . See Also index, storage engine.  Extended SQL syntax for overriding the  indexes  recommended by the optimizer. For example, the  FORCE INDEX ,  USE INDEX , and  IGNORE INDEX  clauses. Typically used when indexed columns have unevenly distributed values, resulting in inaccurate  cardinality  estimates. See Also cardinality, index.  In an  index  that applies to multiple columns (known as a  composite index ), the initial or leading columns of the index. A query that references the first 1, 2, 3, and so on columns of a composite index can use the index, even if the query does not reference all the columns in the index. See Also composite index, index. See statistics.  A  pseudo-record  in an  index , representing the  gap  below the smallest value in that index. If a transaction has a statement such as  SELECT ... FROM ... WHERE col < 10 FOR UPDATE; , and the smallest value in the column is 5, it is a lock on the infimum record that prevents other transactions from inserting even smaller values such as 0, -10, and so on. See Also gap, index, pseudo-record, supremum record.  The name of the  database  that provides a query interface to the MySQL  data dictionary . (This name is defined by the ANSI SQL standard.) To examine information (metadata) about the database, you can query tables such as  INFORMATION_SCHEMA.TABLES  and  INFORMATION_SCHEMA.COLUMNS , rather than using  SHOW  commands that produce unstructured output. The  INFORMATION_SCHEMA  database also contains tables specific to  InnoDB  that provide a query interface to the  InnoDB  data dictionary. You use these tables not to see how the database is structured, but to get real-time information about the workings of  InnoDB  tables to help with performance monitoring, tuning, and troubleshooting. See Also data dictionary, database, InnoDB.  A MySQL component that combines high performance with  transactional  capability for reliability, robustness, and concurrent access. It embodies the  ACID  design philosophy. Represented as a  storage engine ; it handles tables created or altered with the  ENGINE=INNODB  clause. See Chapter 15,  The InnoDB Storage Engine for architectural details and administration procedures, and Section 8.5, “Optimizing for InnoDB Tables”  for performance advice. In MySQL 5.5 and higher,  InnoDB  is the default storage engine for new tables and the  ENGINE=INNODB  clause is not required. InnoDB  tables are ideally suited for  hot backups . See Section 30.2, “MySQL Enterprise Backup Overview”  for information about the  MySQL Enterprise Backup  product for backing up MySQL servers without interrupting normal processing. 6159 InnoDB INFORMATION_SCHEMA infimum record index statistics index prefix index hint index condition pushdown