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https://issues.apache.org/jira/browse/DRILL-3652?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Bridget Bevens resolved DRILL-3652.
-----------------------------------
Resolution: Fixed
Fix Version/s: (was: Future)
1.2.0
Updated the Usage Notes section in Introduction to Window Functions with a note
about this.
> Need to document order of operations with window functions and flatten
> ----------------------------------------------------------------------
>
> Key: DRILL-3652
> URL: https://issues.apache.org/jira/browse/DRILL-3652
> Project: Apache Drill
> Issue Type: Improvement
> Components: Documentation
> Affects Versions: 1.2.0
> Reporter: Victoria Markman
> Labels: window_function
> Fix For: 1.2.0
>
>
> In standard SQL, window functions are the last set of operations performed in
> a query except for the final order by clause.
> Using window function with flatten is a bit confusing, because it appears as
> an operator in the query plan and I expected flatten to run first followed by
> a window function.
> This is not what is happening:
> {code}
> 0: jdbc:drill:schema=dfs> select * from `complex.json`;
> +----+-----------+----------+
> | x | y | z |
> +----+-----------+----------+
> | 5 | a string | [1,2,3] |
> +----+-----------+----------+
> 1 row selected (0.128 seconds)
> 0: jdbc:drill:schema=dfs> select sum(x) over(), x , y, flatten(z) from
> `complex.json`;
> +---------+----+-----------+---------+
> | EXPR$0 | x | y | EXPR$3 |
> +---------+----+-----------+---------+
> | 5 | 5 | a string | 1 |
> | 5 | 5 | a string | 2 |
> | 5 | 5 | a string | 3 |
> +---------+----+-----------+---------+
> 3 rows selected (0.152 seconds)
> 0: jdbc:drill:schema=dfs> explain plan for select sum(x) over(), x , y,
> flatten(z) from `complex.json`;
> +------+------+
> | text | json |
> +------+------+
> | 00-00 Screen
> 00-01 ProjectAllowDup(EXPR$0=[$0], x=[$1], y=[$2], EXPR$3=[$3])
> 00-02 Project(w0$o0=[$3], x=[$0], y=[$1], EXPR$3=[$4])
> 00-03 Flatten(flattenField=[$4])
> 00-04 Project(EXPR$0=[$0], EXPR$1=[$1], EXPR$2=[$2], EXPR$3=[$3],
> EXPR$5=[$2])
> 00-05 Project(x=[$1], y=[$2], z=[$3], w0$o0=[$4])
> 00-06 Window(window#0=[window(partition {} order by [] range
> between UNBOUNDED PRECEDING and UNBOUNDED FOLLOWING aggs [SUM($1)])])
> 00-07 Project(T38¦¦*=[$0], x=[$1], y=[$2], z=[$3])
> 00-08 Scan(groupscan=[EasyGroupScan
> [selectionRoot=maprfs:/drill/testdata/subqueries/complex.json, numFiles=1,
> columns=[`*`], files=[maprfs:///drill/testdata/subqueries/complex.json]]]
> {code}
> We should suggest to users to put flatten in a subquery if they want to run
> window function on top of the result set returned by flatten.
> {code}
> 0: jdbc:drill:schema=dfs> select x, y, a, sum(x) over() from ( select x , y,
> flatten(z) as a from `complex.json`);
> +----+-----------+----+---------+
> | x | y | a | EXPR$3 |
> +----+-----------+----+---------+
> | 5 | a string | 1 | 15 |
> | 5 | a string | 2 | 15 |
> | 5 | a string | 3 | 15 |
> +----+-----------+----+---------+
> 3 rows selected (0.145 seconds)
> {code}
> I suggest we document this issue in the window function section, perhaps in
> "Usage notes".
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