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https://issues.apache.org/jira/browse/DRILL-7330?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17059452#comment-17059452
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ASF GitHub Bot commented on DRILL-7330:
---------------------------------------

paul-rogers commented on pull request #2026: DRILL-7330: Implement metadata 
usage for all format plugins
URL: https://github.com/apache/drill/pull/2026#discussion_r392608220
 
 

 ##########
 File path: 
exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/scan/file/FileMetadataColumn.java
 ##########
 @@ -65,6 +82,11 @@ public FileMetadataColumn(String name, 
FileMetadataColumnDefn defn) {
 
   @Override
   public MetadataColumn resolve(FileMetadata fileInfo, VectorSource source, 
int sourceIndex) {
-    return new FileMetadataColumn(name(), defn, fileInfo, source, sourceIndex);
+    if (value() == null) {
+      return new FileMetadataColumn(name(), defn, fileInfo, source, 
sourceIndex);
+    } else {
+      // case of metadata column, which should have null value independently 
of its column definition
+      return new FileMetadataColumn(name(), defn, (String) null, source, 
sourceIndex);
 
 Review comment:
   Please explain this a bit more. In the original implementation, the reader 
is given a path to a file to read. The path and file name are broken apart and 
passed to these implicit column objects. (I should rename them.) In what case 
would the reader not know the name or path of the file it should read, and must 
look the data up in the metastore? Did we add new columns that require going 
out to the file system to gather a value? (I'm changing this area, so I want to 
make sure I know the intent here.)
   
   If this class will check the fs, then there is a chance the file has been 
deleted. It will now be this class, rather than the reader, that detects 
missing files. I would think we'd want to handle that further up the call 
stack, then pass the resolved info into this class.
 
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> Implement metadata usage for text format plugin
> -----------------------------------------------
>
>                 Key: DRILL-7330
>                 URL: https://issues.apache.org/jira/browse/DRILL-7330
>             Project: Apache Drill
>          Issue Type: Sub-task
>            Reporter: Arina Ielchiieva
>            Assignee: Vova Vysotskyi
>            Priority: Major
>             Fix For: 1.18.0
>
>
> 1. Change the current group scan to leverage Schema from Metastore;
> 2. Use stats for enabling additional logical planning rules for text format 
> plugin. It will enable such optimizations as limit, filter push and so on.
> + add possibility to pass schema through schema file (using path or table 
> root), inline.
> + check for other enhancements in analyze command



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