2.6 Cursors

The RWDBCursor class of the DB Interface Module is implemented for Client-Library using Client-Library ct_cursor() routines. These routines are subject to many restrictions:

• Client-Library cursors are not scrollable; the only type of fetch supported is RWDBCursor::Next. Other types of fetch result in an "Unsupported" error.

• There must be a unique index on every table involved in every cursor operation. An error results if any table does not have a unique index.

• Since Client-Library supports server side cursors, updating a primary key column may result in problems such as multiple updates to the same row. In general, applications should only update nonprimary key columns. Neither this Access Module nor Client-Library prevents the application from updating a primary key column.

• The application can control the number of rows fetched from the server to improve network performance. (See Section 2.16, "Contents of RWDBSystemHandle.") Regardless of the number of rows fetched from the server, calling RWDBCursor::fetchRow() always returns a single row and the rest of the rows are internally buffered within Client-Library.

• In the case of multiple row fetches, the current row as perceived by the server is not the same as the current row as perceived by the application. Client-Library implements updates for the current row as perceived by the application.

© Copyright Rogue Wave Software, Inc. All Rights Reserved.
Rogue Wave and SourcePro are registered trademarks of Rogue Wave Software, Inc. in the United States and other countries. All other trademarks are the property of their respective owners.
Contact Rogue Wave about documentation or support issues.