When you read data from Amazon Redshift, you can configure partitioning to optimize the mapping performance at run time. The partition type controls how the Secure Agent distributes data among partitions at partition points. You cannot configure source partitioning when you run an elastic mapping.
You can define the partition type as key range partitioning. Configure key range partitioning to partition Amazon Redshift data based on the value of a fields or set of fields. With key range partitioning, the Secure Agent distributes rows of source data based the fields that you define as partition keys. The Secure Agent compares the field value to the range values for each partition and sends rows to the appropriate partition.
Use key range partitioning for columns that have an even distribution of data values. Otherwise, the partitions might have unequal size. For example, a column might have 10 rows between key values 1 and 1000 and the column might have 999 rows between key values 1001 and 2000.
With key range partitioning, a query for one partition might return rows sooner than another partition. Or, one partition can return rows while the other partitions are not returning rows. This situation occurs when the rows in the table are in a similar order as the key range. One query might be reading and returning rows while the other queries are reading and filtering the same rows.
You can configure a partition key only of the Integer and String data types.
When you configure more than two partitions in a mapping, the Secure Agent ignore the values that you specify in the start range for the first partition and end range for the last partition. The Secure Agent uses the start range value for the first partition as less than 10 and the end range value for the last partition as greater than the value you specify for the last partition.
For example, if you configure three partitions in a mapping and specify the start range value for the first partition as 5 and the end range value for the last partition as 90, the mapping runs successfully. However, the Secure Agent ignores the values that you specify and uses the start range value for the first partition as less than 10 and the end range value for the last partition as greater than 90.
When you configure key range partitioning for the source and create a target, the mapping task fails.
You cannot configure filters when you use source partitioning.