Example of Pushdown Optimization for Session with Multiple Partitions
Example of Pushdown Optimization for Session with Multiple Partitions
The following figure shows a mapping that contains a Sorter transformation with hash auto-keys partitioning:
The first key range is 1313 - 3340, and the second key range is 3340 - 9354. The SQL statement merges all the data into the first partition:
SELECT ITEMS.ITEM_ID, ITEMS.ITEM_NAME, ITEMS.ITEM_DESC FROM ITEMS1 ITEMS WHERE (ITEMS.ITEM_ID >= 1313) AND (ITEMS.ITEM_ID < 9354) ORDER BY ITEMS.ITEM_ID
The SQL statement selects items 1313 through 9354, which includes all values in the key range, and merges the data from both partitions into the first partition.
The SQL statement for the second partition passes empty data:
SELECT ITEMS.ITEM_ID, ITEMS.ITEM_NAME, ITEMS.ITEM_DESC FROM ITEMS1 ITEMS WHERE (1 = 0) ORDER BY ITEMS.ITEM_ID