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From "Mehant Baid (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (DRILL-2309) Selecting count(), avg() of nullable columns causes wrong results
Date Thu, 19 Mar 2015 02:44:39 GMT

     [ https://issues.apache.org/jira/browse/DRILL-2309?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Mehant Baid resolved DRILL-2309.
--------------------------------
    Resolution: Fixed

Fixed in 12a7d01791bb9ad0126f2dccf2100f09668861d1

> Selecting count(), avg() of nullable columns causes wrong results
> -----------------------------------------------------------------
>
>                 Key: DRILL-2309
>                 URL: https://issues.apache.org/jira/browse/DRILL-2309
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Execution - Data Types
>    Affects Versions: 0.8.0
>            Reporter: Chun Chang
>            Assignee: Mehant Baid
>            Priority: Critical
>             Fix For: 0.9.0
>
>         Attachments: DRILL-2309.patch
>
>
> #Thu Feb 19 18:40:10 EST 2015
> git.commit.id.abbrev=1ceddff
> The following query returns correct count involving columns that contains null value.
> {code}
> 0: jdbc:drill:schema=dfs.drillTestDirComplexJ> select tt.gbyi, count(tt.nul) from
(select t.id, t.gbyi, t.fl, t.nul from `complex.json` t) tt group by tt.gbyi order by tt.gbyi;
> +------------+------------+
> |    gbyi    |   EXPR$1   |
> +------------+------------+
> | 0          | 33580      |
> | 1          | 33317      |
> | 2          | 33438      |
> | 3          | 33535      |
> | 4          | 33369      |
> | 5          | 32990      |
> | 6          | 33661      |
> | 7          | 33130      |
> | 8          | 33362      |
> | 9          | 33364      |
> | 10         | 33229      |
> | 11         | 33567      |
> | 12         | 33379      |
> | 13         | 33045      |
> | 14         | 33305      |
> +------------+------------+
> {code}
> But if you add more aggregation to the query, the returned count is wrong (pay attention
to the last column). 
> {code}
> 0: jdbc:drill:schema=dfs.drillTestDirComplexJ> select tt.gbyi, sum(tt.id), avg(tt.fl),
count(tt.nul) from (select t.id, t.gbyi, t.fl, t.nul from `complex.json` t) tt group by tt.gbyi
order by tt.gbyi;
> +------------+------------+------------+------------+
> |    gbyi    |   EXPR$1   |   EXPR$2   |   EXPR$3   |
> +------------+------------+------------+------------+
> | 0          | 33445554017 | 499613.0956877819 | 66943      |
> | 1          | 33209358334 | 500760.0252919893 | 66318      |
> | 2          | 33369118041 | 498091.82200273 | 66994      |
> | 3          | 33254533860 | 498696.5063226428 | 66683      |
> | 4          | 33393965595 | 501125.64656145993 | 66638      |
> | 5          | 33216885506 | 499961.32710397616 | 66439      |
> | 6          | 33380205950 | 498875.3923256599 | 66911      |
> | 7          | 33405849390 | 501093.43067788356 | 66666      |
> | 8          | 33136951190 | 498458.1044031481 | 66479      |
> | 9          | 33319291474 | 499967.5392457864 | 66643      |
> | 10         | 33339388887 | 499190.47462408233 | 66787      |
> | 11         | 33571590550 | 502095.86682194035 | 66863      |
> | 12         | 33437342090 | 501708.8141502653 | 66647      |
> | 13         | 33071800925 | 498896.453904129 | 66290      |
> | 14         | 33448664191 | 501487.4206955959 | 66699      |
> +------------+------------+------------+------------+
> [code}
> plan for the query returned the wrong result:
> {code}
> 0: jdbc:drill:schema=dfs.drillTestDirComplexJ> explain plan for select tt.gbyi, sum(tt.id),
avg(tt.fl), count(tt.nul) from (select t.id, t.gbyi, t.fl, t.nul from `complex.json` t) tt
group by tt.gbyi order by tt.gbyi;
> +------------+------------+
> |    text    |    json    |
> +------------+------------+
> | 00-00    Screen
> 00-01      Project(gbyi=[$0], EXPR$1=[$1], EXPR$2=[$2], EXPR$3=[$3])
> 00-02        SingleMergeExchange(sort0=[0 ASC])
> 01-01          SelectionVectorRemover
> 01-02            Sort(sort0=[$0], dir0=[ASC])
> 01-03              Project(gbyi=[$0], EXPR$1=[CASE(=($2, 0), null, $1)], EXPR$2=[CAST(/(CastHigh(CASE(=($4,
0), null, $3)), $4)):ANY], EXPR$3=[$5])
> 01-04                HashAgg(group=[{0}], agg#0=[$SUM0($1)], agg#1=[$SUM0($2)], agg#2=[$SUM0($3)],
agg#3=[$SUM0($4)], EXPR$3=[$SUM0($5)])
> 01-05                  HashToRandomExchange(dist0=[[$0]])
> 02-01                    HashAgg(group=[{0}], agg#0=[$SUM0($1)], agg#1=[COUNT($1)], agg#2=[$SUM0($2)],
agg#3=[COUNT($2)], EXPR$3=[COUNT()])
> 02-02                      Project(gbyi=[$3], id=[$2], fl=[$1], nul=[$0])
> 02-03                        Scan(groupscan=[EasyGroupScan [selectionRoot=/drill/testdata/complex_type/json/complex.json,
numFiles=1, columns=[`gbyi`, `id`, `fl`, `nul`], files=[maprfs:/drill/testdata/complex_type/json/complex.json]]])
> {code}



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