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From "Khurram Faraaz (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DRILL-2849) Difference in query results over CSV file created by CTAS, compared to results over original CSV file
Date Wed, 22 Apr 2015 22:26:58 GMT
Khurram Faraaz created DRILL-2849:
-------------------------------------

             Summary: Difference in query results over CSV file created by CTAS, compared
to results over original CSV file 
                 Key: DRILL-2849
                 URL: https://issues.apache.org/jira/browse/DRILL-2849
             Project: Apache Drill
          Issue Type: Bug
          Components: Storage - Text & CSV
    Affects Versions: 0.9.0
         Environment: 64e3ec52b93e9331aa5179e040eca19afece8317 | DRILL-2611: value vectors
should report valid value count | 16.04.2015 @ 13:53:34 EDT
            Reporter: Khurram Faraaz
            Assignee: Steven Phillips


Different results are seen for the same query over CSV data file and another CSV data file
created by CTAS using the same CSV file.
Tests were executed on 4 node cluster on CentOS.
I got rid of the header information that is written by CTAS into the new CSV file that CTAS
creates, and then ran my queries over CTAS' CSV file.

{code}
query over uncompressed CSV file, deletions/deletions-00000-of-00020.csv

select count(cast(columns[0] as double)),max(cast(columns[0] as double)),min(cast(columns[0]
as double)),avg(cast(columns[0] as double)), columns[7] from `deletions/deletions-00000-of-00020.csv`
group by columns[7];

88 rows selected (6.893 seconds)

=================================================

query over CSV file that was created by CTAS. (input to CTAS was deletions/deletions-00000-of-00020.csv)
Notice there is one more record returned.

select count(cast(columns[0] as double)),max(cast(columns[0] as double)),min(cast(columns[0]
as double)),avg(cast(columns[0] as double)), columns[7] from `csvToCSV_00000_of_00020/0_0_0.csv`
group by columns[7];
 
89 rows selected (6.623 seconds)

==================================================

query over compressed CSV file

select count(cast(columns[0] as double)),max(cast(columns[0] as double)),min(cast(columns[0]
as double)),avg(cast(columns[0] as double)), columns[7] from `deletions-00000-of-00020.csv.gz`
group by columns[7];

88 rows selected (10.526 seconds)

==================================================

In the below cases, the count and sum results are different when query is executed over CSV
file that was created by CTAS. ( this may explain why we see the difference in results in
the above queries ? )

0: jdbc:drill:> select count(cast(columns[0] as double)),max(cast(columns[0] as double)),min(cast(columns[0]
as double)),avg(cast(columns[0] as double)), columns[7] from `deletions/deletions-00000-of-00020.csv`
where columns[7] is null group by columns[7];
+------------+------------+------------+------------+------------+
|   EXPR$0   |   EXPR$1   |   EXPR$2   |   EXPR$3   |   EXPR$4   |
+------------+------------+------------+------------+------------+
| 252        | 1.362983396001E12 | 1.165768779027E12 | 1.293794515595635E12 | null       |
+------------+------------+------------+------------+------------+
1 row selected (6.013 seconds)

0: jdbc:drill:> select count(cast(columns[0] as double)),max(cast(columns[0] as double)),min(cast(columns[0]
as double)),avg(cast(columns[0] as double)), columns[7] from `deletions-00000-of-00020.csv.gz`
where columns[7] is null group by columns[7];
+------------+------------+------------+------------+------------+
|   EXPR$0   |   EXPR$1   |   EXPR$2   |   EXPR$3   |   EXPR$4   |
+------------+------------+------------+------------+------------+
| 252        | 1.362983396001E12 | 1.165768779027E12 | 1.293794515595635E12 | null       |
+------------+------------+------------+------------+------------+
1 row selected (8.899 seconds)

Notice that count and sum results are different (from those above) when query is executed
over the CSV file created by CTAS.

0: jdbc:drill:> select count(cast(columns[0] as double)),max(cast(columns[0] as double)),min(cast(columns[0]
as double)),avg(cast(columns[0] as double)), columns[7] from `csvToCSV_00000_of_00020/0_0_0.csv`
where columns[7] is null group by columns[7];
+------------+------------+------------+------------+------------+
|   EXPR$0   |   EXPR$1   |   EXPR$2   |   EXPR$3   |   EXPR$4   |
+------------+------------+------------+------------+------------+
| 245        | 1.349670663E12 | 1.165768779027E12 | 1.2930281335065144E12 | null       |
+------------+------------+------------+------------+------------+
1 row selected (5.736 seconds)

{code}



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