/*+ FORCE_SPLIT_COLUMN */
SELECT column_name /*+FORCE_SPLIT_COLUMN */, col2, col3, ... FROM fromClause;
Choose a split column with a high cardinality; choose a column wherein the values in the rows of that column contain a very high percentage of unique values. High cardinality columns will assist in efficiently splitting the data and parallelizing the work processing.
For this hint to be considered by the optimizer, there must be a movement between two federated systems involved in query processing. If the query only queries a single system, then the hint may be ignored by the optimizer.
This query combines a force runmode hint with force split column.
The movement from MYSQL to HIVE will be parallelized in the Sqoop import step, splitting the data on the “double_value + 1” column.
SELECT /*+FORCE_RUNMODE('HIVE_CDH') */ join1_id, double_value + 1 /*+FORCE_SPLIT_COLUMN */, upper_letters FROM ( SELECT join1_id, double_value + 123 double_value, upper_letters FROM MYSQL.inventory.dbo.TSTMSTR_JOIN1 ) a;