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https://issues.apache.org/jira/browse/DRILL-4349?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Khurram Faraaz closed DRILL-4349.
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> 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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