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Posted to issues@drill.apache.org by "Jason Altekruse (JIRA)" <ji...@apache.org> on 2014/12/12 22:46:14 UTC
[jira] [Created] (DRILL-1858) Parquet reader should only explicitly
fill in data for a column requested but not in the file if there are no
valid columns found
Jason Altekruse created DRILL-1858:
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Summary: Parquet reader should only explicitly fill in data for a column requested but not in the file if there are no valid columns found
Key: DRILL-1858
URL: https://issues.apache.org/jira/browse/DRILL-1858
Project: Apache Drill
Issue Type: Improvement
Reporter: Jason Altekruse
If columns are requested from a parquet file, that do not appear in the particular file (users may have a directory full of files that share some columns but not others) then we do not need to create a vector to represent these columns in most cases. These columns can be materialized (as a vector filled with nulls) later when they are referenced in other parts of the query, such as a filter or join condition. The current behavior of the reader is to always fill vectors for these types of columns, but this just creates extra payload to ship around until the vectors are actually referenced.
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