Deneche A. Hakim created DRILL-4267:
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Summary: Multiple window function operators instead of one
Key: DRILL-4267
URL: https://issues.apache.org/jira/browse/DRILL-4267
Project: Apache Drill
Issue Type: Bug
Components: Query Planning & Optimization
Affects Versions: 1.5.0
Reporter: Deneche A. Hakim
Priority: Minor
Changing the order of window functions in a query changes the number of window
function operators in the plan.
The following query generates a plan with a single window function operator:
{noformat}
0: jdbc:drill:zk=local> EXPLAIN PLAN FOR SELECT ROW_NUMBER() OVER w, COUNT(*)
OVER w FROM cp.`employee.json` WINDOW w AS (PARTITION BY position_id ORDER BY
salary);
+------+------+
| text | json |
+------+------+
| 00-00 Screen
00-01 Project(EXPR$0=[$0], EXPR$1=[$1])
00-02 Project(EXPR$0=[$0], EXPR$1=[$1])
00-03 Project($0=[$2], $1=[$3])
00-04 Window(window#0=[window(partition {0} order by [1] rows
between UNBOUNDED PRECEDING and CURRENT ROW aggs [ROW_NUMBER(), COUNT()])])
00-05 SelectionVectorRemover
00-06 Sort(sort0=[$0], sort1=[$1], dir0=[ASC], dir1=[ASC])
00-07 Scan(groupscan=[EasyGroupScan
[selectionRoot=classpath:/employee.json, numFiles=1, columns=[`position_id`,
`salary`], files=[classpath:/employee.json]]])
{noformat}
But when we permute the window functions in the query we get 2 window function
operators in the plan:
{noformat}
0: jdbc:drill:zk=local> EXPLAIN PLAN FOR SELECT COUNT(*) OVER w, ROW_NUMBER()
OVER w FROM cp.`employee.json` WINDOW w AS (PARTITION BY position_id ORDER BY
salary);
+------+------+
| text | json |
+------+------+
| 00-00 Screen
00-01 Project(EXPR$0=[$0], EXPR$1=[$1])
00-02 Project(EXPR$0=[$0], EXPR$1=[$1])
00-03 Project($0=[$2], $1=[$3])
00-04 Window(window#0=[window(partition {0} order by [1] rows
between UNBOUNDED PRECEDING and CURRENT ROW aggs [ROW_NUMBER()])])
00-05 Window(window#0=[window(partition {0} order by [1] range
between UNBOUNDED PRECEDING and CURRENT ROW aggs [COUNT()])])
00-06 SelectionVectorRemover
00-07 Sort(sort0=[$0], sort1=[$1], dir0=[ASC], dir1=[ASC])
00-08 Scan(groupscan=[EasyGroupScan
[selectionRoot=classpath:/employee.json, numFiles=1, columns=[`position_id`,
`salary`], files=[classpath:/employee.json]]])
{noformat}
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