When merging partitions that were created by specifying data slices in the Partition wizard, the merged partition can contain unexpected incorrect data after it is processed. To prevent this, you can create a filter that specifies the data in the resultant partition.
For example, a cube containing information about three soft drink products has three partitions that use the same fact table. These partitions are based on slicing by product. Partition 1 contains data about [ColaFull], Partition 2 contains data about [ColaDecaf], and Partition 3 contains data about [ColaDiet]. If Partition 3 is merged into Partition 2, the data in the merged partition (Partition 2) will be correct and the cube data will be accurate. However, when Partition 2 is processed, its content will be specified by the parent of the product level, which is [SoftDrinks]. This parent level also includes [ColaFull], the product in Partition 1. Processing Partition 2 loads the partition with data for all soft drinks, including [ColaFull]. The cube then contains duplicate data for [ColaFull] and will return incorrect data to users.
In this example, after merging Partition 3 into Partition 2, you can provide a filter such as (“Product” = ‘ColaDecaf’ OR “Product” = ‘ColaDiet’) to specify the data in the combined Partition 2 to extract only data about [ColaDecaf] and [ColaDiet] from the fact table, excluding data pertaining to [ColaFull]. When the partition is processed, the cube will not contain duplicate data.