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SQL Anywhere 12.0.0 » UltraLite - Database Management and Reference » Using UltraLite databases » UltraLite performance and optimization


Choosing an optimal hash size

The UltraLite default maximum hash size of 4 bytes was chosen to suit most deployments. You can increase the size to include more data with the row ID. However, this change could increase the size of the index and fragment it among multiple pages. This change can possibly increase the size of the database as a result. The impact of an increased maximum hash size depends on the number of rows in the table: for example, if you only have a few rows, a large index hash key would still fit on the index page. No index fragmentation occurs in this case.

When choosing an optimal hash size, consider the data type, the row data, and the database size (especially if a table contains many rows).

The only way to determine if you have chosen an optimal hash size is to run benchmark tests against your UltraLite client application on the target device. You need to observe how various hash sizes affect the application and query performance, in addition to the changes in database size itself.

 The data type
 The row data
 The database size
 See also