See Also full-text search, FULLTEXT index. 

## index condition pushdown 

 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. 

## index hint 

 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. 

## index prefix 

 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. 

## index statistics 

See statistics. 

## infimum record 

 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. 

## INFORMATION_SCHEMA 

 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. 

## 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. 

