vvysotskyi commented on pull request #2092:
URL: https://github.com/apache/drill/pull/2092#issuecomment-660886165


   @cgivre, there already was a similar functionality for Parquet: 
https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/columnreaders/ParquetRecordReader.java#L53.
   Please take a look at 
[`AbstractGroupScanWithMetadata.applyLimit()`](https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/physical/base/AbstractGroupScanWithMetadata.java#L453)
 method - it contains required logic for pruning files. With your changes, you 
are overriding it, so it breaks this functionality. To coexist with this 
feature, please take a look at the implementation of this method for the 
parquet group scan, move common logic to AbstractGroupScanWithMetadata and use 
it in the easy group scan.
   
   The behavior with the metastore usage is the following: if for example, we 
have 10 files with 100 records, and query with limit 5 is submitted, only the 
single file would be left in the group scan, since it contains all required 
records.


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