Count Distinct with Partitions

Count Distinct with Partitions is an advanced property that is hidden by default. For information on how to display this property, see Viewing and Changing Advanced VLDB Properties.

This property can help improve the performance of queries performed on multiple partitioned tables which return a distinct count of values. A distinct count of values allows you to return information such as how many distinct types of items were sold on a given day. You have the following options:

• Do not select distinct elements for each partition (default): To return a distinct count of values from multiple partition tables, the tables are first combined together as one large result table, and then the count distinct calculation is performed. While this returns the proper results, combining multiple tables into one table to perform the count distinct calculation can be a resource-intensive query.
• Select distinct elements for each partition: To return a distinct count of values from multiple partitioned tables, the size of each partition table is first reduced by returning only distinct values. These smaller tables are then combined and a count distinct calculation is performed. This can improve performance by reducing the size of the partition tables before they are combined for the final count distinct calculation.

Levels at Which You Can Set This

Metric, report, template, and database instance