Github user amansinha100 commented on a diff in the pull request:
https://github.com/apache/drill/pull/519#discussion_r68678168
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/store/dfs/FileSelection.java
---
@@ -47,16 +47,25 @@
private List<FileStatus> statuses;
public List<String> files;
+ /**
+ * root path for the selections
+ */
public final String selectionRoot;
+ /**
+ * root path for the metadata cache file (if any)
+ */
+ public final String cacheFileRoot;
--- End diff --
That was my initial approach (updating the selectionRoot without keeping a
separate cacheFileRoot). However, I ran into a few issues. The main one
that I recall is that the dir0, dir1 etc columns are associated with the
selectionRoot, so suppose I run the following query:
SELECT dir0, dir1 FROM dfs.tmp.t2 WHERE dir0=2015 AND dir1='Q1'
and if the selectionRoot gets modified to point to '2015/Q1' then we have
lost the context of the original dir0, dir1 because everything will become
relative to the new selectionRoot. This produces wrong results. The same
problem occurred with a SELECT * query where the directory columns where not
showing up correctly.
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