[jira] [Commented] (DRILL-7279) Support provided schema for CSV without headers

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-7279?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16854786#comment-16854786 ] 

ASF GitHub Bot commented on DRILL-7279:
---------------------------------------

arina-ielchiieva commented on pull request #1798: DRILL-7279: Enable provided schema for text files without headers
URL: https://github.com/apache/drill/pull/1798#discussion_r289925557
 
 

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 File path: exec/java-exec/src/main/java/org/apache/drill/exec/store/easy/text/compliant/v3/CompliantTextBatchReader.java
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 @@ -122,10 +122,12 @@ public boolean open(ColumnsSchemaNegotiator schemaNegotiator) {
 
   /**
    * Extract header and use that to define the reader schema.
+   * @param strings
 
 Review comment:
   Same here.
 
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> Support provided schema for CSV without headers
> -----------------------------------------------
>
>                 Key: DRILL-7279
>                 URL: https://issues.apache.org/jira/browse/DRILL-7279
>             Project: Apache Drill
>          Issue Type: Improvement
>    Affects Versions: 1.16.0
>            Reporter: Paul Rogers
>            Assignee: Paul Rogers
>            Priority: Major
>             Fix For: 1.17.0
>
>
> Extend the Drill 1.16 provided schema support for the text reader to allow a provided schema for files without headers. Behavior:
> * If the file is configured to not extract headers, and a schema is provided, and the schema has at least one column, then use the provided schema to create individual columns. Otherwise, continue to use {{columns}} as in previous versions.
> * The columns in the schema are assumed to match left-to-right with those in the file.
> * If the schema contains more columns than the file, the extra columns take their default values. (This occurs in schema evolution when a column is added to newer files.)
> * If the file contains more columns than the schema, then the extra columns, at the end of the line, are ignored. This is the same behavior as occurs if the file contains headers.
> h4. Table Properties
> Also adds four table properties for text files. These properties, if present, override those defined in the format plugin configuration. The properties allow the user to have a single "csv" config, but to have many tables with the "csv" suffix, each with different properties. That is, the user need not define a new plugin config, and define a new extension, just to change a file format property. With this system, the user can have a ".csv" file with headers; the user need not define a different suffix (usually ".csvh" in Drill) for this case.
> || Table Property || Equivalent Plugin Config Property ||
> | {{drill.headers}} | {{extractHeader}} |
> | {{drill.skipFirstLine}} |  {{skipFirstLine}} | 
> | {{drill.delimiter}} |  {{fieldDelimiter}} | 
> |  {{drill.commentChar}} |  {{comment}}| 
> For each, the rules are:
> * If the table property is not set, then the plugin property is used.
> * If the table property is set, then the property value replaces the plugin property value for that one specific table.
> * For the delimiter, if the property value is an empty string, then this is the same as an unset property.
> * For the comment, if the property value is an empty string, then the comment is set to the ASCII NULL, which will never match. This effectively turns off the comment feature for this one table.
> * If the delimiter or comment value is longer than a single character, only the first character is used.
> It is possible to use the table properties without specifying a "provided" schema. Just omit any columns from the schema:
> {noformat}
> create schema () for table `dfs.data`.`example`
> PROPERTIES ('drill.headers'='false', 'drill.skipFirstLine'='false', 'drill.delimiter'='|')
> {noformat}



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