Victoria Markman created DRILL-3420:
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Summary: Final sort can be dropped in some cases when result of
window operator is already sorted on the same columns
Key: DRILL-3420
URL: https://issues.apache.org/jira/browse/DRILL-3420
Project: Apache Drill
Issue Type: Bug
Components: Query Planning & Optimization
Affects Versions: 1.0.0
Reporter: Victoria Markman
Assignee: Jinfeng Ni
Fix For: 1.2.0
In the example query, output of the window operator is already sorted on the
same columns that are specified in "order by clause" Last sort is redundant.
{code}
0: jdbc:drill:schema=dfs> explain plan for select b1, c1, a1, sum(a1)
over(partition by b1 order by c1, a1) from t1 order by 1,2,3;
+------+------+
| text | json |
+------+------+
| 00-00 Screen
00-01 Project(b1=[$0], c1=[$1], a1=[$2], EXPR$3=[$3])
00-02 SelectionVectorRemover
00-03 Sort(sort0=[$0], sort1=[$1], sort2=[$2], dir0=[ASC], dir1=[ASC],
dir2=[ASC])
00-04 Project(b1=[$0], c1=[$1], a1=[$2], EXPR$3=[CASE(>($3, 0), $4,
null)])
00-05 Window(window#0=[window(partition {0} order by [1, 2] range
between UNBOUNDED PRECEDING and CURRENT ROW aggs [COUNT($2), $SUM0($2)])])
00-06 SelectionVectorRemover
00-07 Sort(sort0=[$0], sort1=[$1], sort2=[$2], dir0=[ASC],
dir1=[ASC], dir2=[ASC])
00-08 Scan(groupscan=[ParquetGroupScan
[entries=[ReadEntryWithPath [path=maprfs:///drill/testdata/subqueries/t1]],
selectionRoot=/drill/testdata/subqueries/t1, numFiles=1, columns=[`b1`, `c1`,
`a1`]]])
{code}
Note to QA: when this enhancement is implemented, we need to make sure that we
have cases where sort order is destroyed by subsequent operation on top of
window. In these cases "sort should still be planned.
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