[jira] [Created] (DRILL-6318) Push down limit into flatten is incorrect

["Oleg Zinoviev (JIRA)" <ji...@apache.org>]

Oleg Zinoviev created DRILL-6318:
------------------------------------

             Summary: Push down limit into flatten is incorrect
                 Key: DRILL-6318
                 URL: https://issues.apache.org/jira/browse/DRILL-6318
             Project: Apache Drill
          Issue Type: Bug
         Environment: Ubuntu Mate 18.04

Apache Drill 1.14.0-SNAPSHOT
            Reporter: Oleg Zinoviev
             Fix For: 1.14.0, 1.13.0
         Attachments: sample.json

Sample data: [^sample.json]

Result of
{code:sql}
select flatten(data) as d from dfs.root.`sample.json`
{code}
is
||d||
|Honored Boy Scout|
|Yawning Wolf|
|Closed Queen|
|Innocent Volunteer|
|Junior Wing|
|Lame Mantis|
|Old Master|
|Numb Pawn|
|Hollow Guardian|
|Twin Hurricane|
|Helpless Avalange|

Let's try to get first 3 rows:
{code:sql}
select flatten(data) as d from dfs.root.`sample.json` limit 3
{code}
Result has only 2 rows:
||d||
|Honored Boy Scout|
|Yawning Wolf|

*Reason:* Limit was pushed down below flatten and only 3 top rows from json was selected. In this 3 rows only 2nd has items in "data" field.

Let's try to get 3 rows from the middle:
{code:sql}
select flatten(data) as d from dfs.root.`sample.json` limit 3 offset 5
{code}
Result is empty.

*Reason:* Limit and offset was pushed down below flatten and only 6, 7 and 8 row from json was selected. This 3 rows contains only 3 items in "data" field. After flatten limit and offset applies second time and reject all select items.

Error in org/apache/drill/exec/planner/logical/DrillPushLimitToScanRule.java




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