[KYLIN-1278] Query engine optimization: skip the condition checking on partition column if a segment's time is totaly included in the query range

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: Backlog
• Component/s: Query Engine
• Assignee: liyang
• Reporter: Shao Feng Shi
• Created: 04/Jan/16 03:21
• Updated: 29/Nov/17 07:13
• Resolved: 29/Nov/17 07:13

Description

See an example: a cube (which is partitioned by date column "CAL_DT") has three segments:

S1, S2, S3;

Now a query like "select .... from fact_table where CAL_DT > 'yyyy-mm-dd' group by dimA, dimB..." comes, and the "CAL_DT" is only used for filtering, not in group by;

By checking the startTime/endTime, Kylin found S2 and S3 need be scanned, and S3 is totally match the condition "CAL_DT > yyyy-mm-dd". Then when scan S3, Kylin can ignore the condition on "CAL_DT", selecting a smaller cuboid, this should gain better performance.

Further more, this can be generalized to all filtering condition columns: if all values of a dimension matches with user's filtering condition, and it isn't in "group by", Kylin can ignore that column when selecting the cuboid.