TAJO-1067: INSERT OVERWRITE INTO should not remove all partitions.

[blrunner]

I added new session variable for avoiding remove existing partition directories. Its name is COLUMN_PARITION_REMOVE_ALL_PARTITIONS. Its default value is false. Thus, if you run INSERT OVERWRITE statement with column partitioned table, tajo doesn't remove existing partition directories. Tajo just remove partition directories which is equals to staging directories.

And this patch has a lack that is related to TAJO-744. You left the comment for the lack at TAJO-1067.

[hyunsik]

I think that this feature should not depend on session variable. Session variable works implicitly. Users can miss to check if the session variable is enabled.

As a result, inadvertently, a user can lost his or her entire table by INSERT OVERWRITE clause.

I think that we should force users to manually use TRUNCATE statement instead of using session variable.

[blrunner]

Hi @hyunsik

I agree with your opinion. I've just removed the variable.
If possible, could you check the patch again?

[hyunsik]

COLUMN_PARITION_REMOVE_ALL_PARTITIONS was already removed. So, you need to revise this comment line.

[blrunner]

Hi @hyunsik

Thank you for your detailed review.
I agree with your opinions and I've just updated it.
Could you check it again?

[hyunsik]

'a' is duplicated.

[hyunsik]

Thank you for your work. The patch looks good to me. After I hear your through about my final comments, I'll finish this review.