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From "Deneche A. Hakim (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (DRILL-4349) parquet reader returns wrong results when reading a nullable column that starts with a large number of nulls (>30k)
Date Fri, 05 Feb 2016 01:33:39 GMT

     [ https://issues.apache.org/jira/browse/DRILL-4349?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Deneche A. Hakim resolved DRILL-4349.
-------------------------------------
    Resolution: Fixed

Fixed in ca53c2440fb33e31220d11aee297fee67fc6bd6a

> parquet reader returns wrong results when reading a nullable column that starts with
a large number of nulls (>30k)
> -------------------------------------------------------------------------------------------------------------------
>
>                 Key: DRILL-4349
>                 URL: https://issues.apache.org/jira/browse/DRILL-4349
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Storage - Parquet
>    Affects Versions: 1.4.0
>            Reporter: Deneche A. Hakim
>            Assignee: Deneche A. Hakim
>            Priority: Critical
>             Fix For: 1.6.0
>
>         Attachments: drill4349.tar.gz
>
>
> While reading a nullable column, if in a single pass we only read null values, the parquet
reader resets the value of pageReader.readPosInBytes which will lead to wrong data read from
the file.
> To reproduce the issue, create a csv file (repro.csv) with 2 columns (id, val) with 50100
rows, where id equals to the row number and val is empty for the first 50k rows, and equal
to id for the remaining rows.
> create a parquet table from the csv file:
> {noformat}
> CREATE TABLE `repro_parquet` AS SELECT CAST(columns[0] AS INT) AS id, CAST(NULLIF(columns[1],
'') AS DOUBLE) AS val from `repro.csv`;
> {noformat}
> Now if you query any of the non null values you will get wrong results:
> {noformat}
> 0: jdbc:drill:zk=local> select * from `repro_parquet` where id>=50000 limit 10;
> +--------+---------------------------+
> |   id   |            val            |
> +--------+---------------------------+
> | 50000  | 9.11337776337441E-309     |
> | 50001  | 3.26044E-319              |
> | 50002  | 1.4916681476489723E-154   |
> | 50003  | 2.0000000018890676        |
> | 50004  | 2.681561588521345E154     |
> | 50005  | -2.1016574E-317           |
> | 50006  | -1.4916681476489723E-154  |
> | 50007  | -2.0000000018890676       |
> | 50008  | -2.681561588521345E154    |
> | 50009  | 2.1016574E-317            |
> +--------+---------------------------+
> 10 rows selected (0.238 seconds)
> {noformat}
> and here are the expected values:
> {noformat}
> 0: jdbc:drill:zk=local> select * from `repro.csv` where cast(columns[0] as int)>=50000
limit 10;
> +--------------------+
> |      columns       |
> +--------------------+
> | ["50000","50000"]  |
> | ["50001","50001"]  |
> | ["50002","50002"]  |
> | ["50003","50003"]  |
> | ["50004","50004"]  |
> | ["50005","50005"]  |
> | ["50006","50006"]  |
> | ["50007","50007"]  |
> | ["50008","50008"]  |
> | ["50009","50009"]  |
> +--------------------+
> {noformat}
> I confirmed that the file is written correctly and the issue is in the parquet reader
(already have a fix for it)



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