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From "Khurram Faraaz (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (DRILL-5549) SELECT * against a CSV file with empty headers produces error
Date Thu, 06 Jul 2017 06:44:00 GMT

     [ https://issues.apache.org/jira/browse/DRILL-5549?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Khurram Faraaz updated DRILL-5549:
    Component/s: Storage - Text & CSV

> SELECT * against a CSV file with empty headers produces error
> -------------------------------------------------------------
>                 Key: DRILL-5549
>                 URL: https://issues.apache.org/jira/browse/DRILL-5549
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Storage - Text & CSV
>    Affects Versions: 1.10.0
>            Reporter: Paul Rogers
>            Priority: Minor
> See DRILL-5548 for background. This test is very similar except that the input file has
a single blank line. Since the CSV plugin is set up to read headers, this represents a non-empty
file, with no headers and no data.
> Again use a star query:
> {code}
> SELECT * FROM `dfs.data.emptyHeader.csv`
> {code}
> The result this time is somewhat different:
> {code}
> org.apache.drill.common.exceptions.UserRemoteException: 
> SYSTEM ERROR: HeaderError: The file must define at least one header.
> {code}
> If we fix the issue in DRILL-5548 (empty file), we should use the same solution for a
file with an empty header.
> Suppose the file was not entirely empty, suppose it was:
> {code}
> 1:
> 2: fred
> 3: barney
> {code}
> (Note: line numbers shown to force display of blank line...)
> Here, we have an empty header, but we have data. We can't know that we have data while
reading the header. While this is a pathological case, and an invalid CSV file, this second
case does suggest that the right solution to the two empty cases is to use the special {{columns}}
array when the header is empty. This will allow Drill to gracefully handle the case above
for a file with no header but with data.

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