Managing the Retrieval of Database Meta-Information
Meta-information is information that describes the data stored in the database and can include information about the tables in the database, the columns in those tables, and the indexes that are defined for those tables. This data also is referred to as the database’s data dictionary or system catalog.
Typically, ODBC applications extract and use information from the database’s data dictionary using specific calls, such as the ODBC calls SQLTables, SQLColumns, and SQLPrimaryKeys. In large databases, the amount of meta-information that is retrieved can be considerable. Because some client applications cannot manage large amounts of information efficiently, system performance can be adversely affected.
Some ODBC calls have parameters that accept search patterns. You can use these parameters to limit the amount of meta-information that is retrieved; however, not every client application supports these parameters.
OpenAccess SDK allows you to use database data dictionary filters and database data dictionary views to limit the amount of meta-information that is retrieved.
Using Database Data Dictionary Filters
Database Data Dictionary filters limit the amount of meta-information that can be retrieved from the database’s native data dictionary. Specifically, they limit the number of result rows that can be returned for SQLTables. The data dictionary filters override any call parameters that are passed by the application when it accesses the database’s native data dictionary.
OpenAccess SDK provides the following types of database data dictionary filters, which must be defined on the server:
• Filter by catalog list
• Filter by schema list
• Filter by table type
For more information about setting the database data dictionary filters for an OpenAccess service, refer to "DataSourceSchemaFilterList" in the OpenAccess SDK Administrator’s Guide.
