Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/644#discussion_r86388727
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/ParquetWriter.java
---
@@ -40,6 +40,8 @@
public class ParquetWriter extends AbstractWriter {
static final org.slf4j.Logger logger =
org.slf4j.LoggerFactory.getLogger(ParquetWriter.class);
+ public static final int WRITER_VERSION = 2;
--- End diff --
This deserves an explanation. Something like:
Version of Drill's Parquet writer. Increment this version (by 1) any time
we make any format change to the file. Format changes include 1) supporting new
data types, 2) changes to the format of data fields, 3) adding new metadata to
the file footer, etc.
Newer readers must be able to read old files. The Writer version tells the
Parquet reader how to interpret fields or metadata when that data changes
format from one writer version to another.
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