You can limit the number of rows that are displayed in your report. You can also limit the number of seconds a query runs before a timeout occurs. Imposing row limits and timeouts on queries is important to avoid out-of-memory errors, or processes that consume too many resources on the database server.
Both options are available in the Query Setup dialog box. In the Data tab, click the small icon in the upper-right corner to open the Query Setup dialog box. Make changes as needed and close the dialog box when you are done.
Define Result Row Limit and Timeout has information about refining the row limits and timeouts further with Metadata Editor.