[KYLIN-2841] LIMIT pushdown should be applied to subquery

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: v2.1.0
• Fix Version/s: v2.6.0
• Labels: scope
• Assignee: zhengdong
• Reporter: Mu Kong
• Created: 04/Sep/17 06:18
• Updated: 12/Jan/19 06:41
• Resolved: 14/Dec/18 07:06

Description

Hi, all.

I found that limit in the web UI seems not behaving as expected.

When I run a query like the follows:

SELECT
  SUM(col3) AS col4, 
  SUM(col5) AS total_col5,
  col1 
FROM
(
  SELECT
    col1,
    col2,
    MAX(col3) AS col3,
    COUNT(*) AS col5
  FROM db.table
  WHERE col6 = 'somestring'
  GROUP BY col1, col2
)
GROUP BY col1

When I specify the limit as 50, the result has 19 records, and when I specify the limit as 500000, there are 90+ records in the result and each record has higher col4 and total_col5.
But for query that doesn't have subquery, the result remains the same no matter how I change the limit.

I guess for the query with subquery, limit somehow limits the number of the result from the inner query instead of the result of the outer query.

Issue Links

• is related to: KYLIN-3722 Error Limit Push Down in Join Related Query