Release Notes

22.21 Working with Large Query Results

It is easy for a user to produce a query that returns a large number of rows. It is not so easy for a user to predict how many rows might actually be returned. With a query that could potentially return thousands (or millions) of rows, there are two problems:

1. It can take a long time to retrieve the result.
2. A large amount of client memory can be required to hold the result.

To facilitate this process, DB2 breaks up large result sets into chunks. It will retrieve and display the results of a query one chunk at a time.

As a result:

1. Display time will be reduced as the first chunk of a query is available for viewing while the remaining chunks are being retrieved.
2. Memory requirements on the client will be reduced as only one chunk of a query result will be stored on the client at any given time.

To control the number of query result rows in memory::

1. Open the General page of the Tool Settings notebook.
2. In the Maximum size section, select:
   • Sample Contents to limit the number of result rows displayed in the Sample Contents window. Specify the chunk size of the result set (number of rows) in the entry field.
   • Command Center to limit the number of result rows displayed on the Query Results page of the Command Center. Specify the chunk size of the result set (number of rows) in the entry field.

When working with the results of a query in the Sample Contents window or on the Query Results page of the Command Center, the Rows in memory field indicates the number of rows being held in memory for the query. This number will never be greater than the Maximum size set. Click on Next to retrieve to the next chunk of the result set. When Next is inactive, you have reached the end of the result set.