of main-memory databases. This feature is controlled by the  innodb_adaptive_hash_index  configuration option. Because this feature benefits some workloads and not others, and the memory used for the hash index is reserved in the  buffer pool , typically you should benchmark with this feature both enabled and disabled. The hash index is always built based on an existing  B-tree  index on the table. MySQL can build a hash index on a prefix of any length of the key defined for the B-tree, depending on the pattern of searches against the index. A hash index can be partial; the whole B-tree index does not need to be cached in the buffer pool. In MySQL 5.6 and higher, another way to take advantage of fast single-value lookups with  InnoDB  tables is to use the  InnoDB memcached  plugin. See Section 15.20, “InnoDB memcached Plugin”  for details. See Also B-tree, buffer pool, hash index, memcached, page, secondary index.  An object-relational mapping (ORM) framework for applications built using .NET technologies such as  ASP.NET . Such applications can interface with MySQL through the  Connector/NET  component. See Also .NET, ASP.net, Connector/NET, Mono, Visual Studio. See Also asynchronous I/O.  In  ODBC , an alternative method of supporting character sets and other internationalization aspects. Contrast with Unicode .  Connector/ODBC 3.51 is an ANSI driver, while Connector/ODBC 5.1 is a Unicode driver. See Also Connector/ODBC, ODBC, Unicode.  APIs provide low-level access to the MySQL protocol and MySQL resources from  client  programs. Contrast with the higher-level access provided by a  Connector . See Also C API, client, connector, native C API, Perl API, PHP API, Python API, Ruby API.  A set of functions or procedures. An API provides a stable set of names and types for functions, procedures, parameters, and return values.  When a backup produced by the  MySQL Enterprise Backup  product does not include the most recent changes that occurred while the backup was underway, the process of updating the backup files to include those changes is known as the  apply  step. It is specified by the  apply-log  option of the  mysqlbackup  command. Before the changes are applied, we refer to the files as a  raw backup . After the changes are applied, we refer to the files as a  prepared backup . The changes are recorded in the  ibbackup_logfile  file; once the apply step is finished, this file is no longer necessary. See Also hot backup, ibbackup_logfile, MySQL Enterprise Backup, prepared backup, raw backup.  A framework for developing web-based applications using  .NET  technologies and languages. Such applications can interface with MySQL through the  Connector/NET  component. Another technology for writing server-side web pages with MySQL is  PHP . See Also .NET, ADO.NET, Connector/NET, Mono, PHP, Visual Studio.  A library of compiled code in a  .NET  system, accessed through  Connector/NET . Stored in the  GAC  to allow versioning without naming conflicts. 6132 ADO.NET AIO ANSI  Acronym for  asynchronous I/O . You might see this acronym in  InnoDB  messages or keywords. API application programming interface (API) apply ASP.net assembly