In hash user keys partitioning, the Integration Service uses a hash function to group rows of data among partitions based on a user-defined partition key. You choose the ports that define the partition key:
When you specify hash auto-keys partitioning in the preceding mapping, the Sorter transformation receives rows of data grouped by the sort key, such as ITEM_DESC. If the item description is long, and you know that each item has a unique ID number, you can specify hash user keys partitioning at the Sorter transformation and select ITEM_ID as the hash key. This might improve the performance of the session since the hash function usually processes numerical data more quickly than string data.
If you select hash user keys partitioning at any partition point, you must specify a hash key. The Integration Service uses the hash key to distribute rows to the appropriate partition according to group.
For example, if you specify key range partitioning at a Source Qualifier transformation, the Integration Service uses the key and ranges to create the WHERE clause when it selects data from the source. Therefore, you can have the Integration Service pass all rows that contain customer IDs less than 135000 to one partition and all rows that contain customer IDs greater than or equal to 135000 to another partition.
If you specify hash user keys partitioning at a transformation, the Integration Service uses the key to group data based on the ports you select as the key. For example, if you specify ITEM_DESC as the hash key, the Integration Service distributes data so that all rows that contain items with the same description go to the same partition.
To specify the hash key, select the partition point on the Partitions view of the Mapping tab, and click Edit Keys. This displays the Edit Partition Key dialog box. The Available Ports list displays the connected input and input/output ports in the transformation. To specify the hash key, select one or more ports from this list, and then click Add.
To rearrange the order of the ports that define the key, select a port in the Selected Ports list and click the up or down arrow.