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From "Thomas Tauber-Marshall (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-4622: Add ALTER COLUMN statement.
Date Tue, 23 May 2017 16:41:26 GMT
Thomas Tauber-Marshall has posted comments on this change.

Change subject: IMPALA-4622: Add ALTER COLUMN statement.
......................................................................


Patch Set 2:

> To be a bit more prescriptive than my last comment:
 > 
 > Can you see how much of this new functionality you can actually
 > accomplish using the change syntax given it's already there?
 > 
 > I think we'll have a harder time justifying this new syntax to
 > accomplish something you can technically already do, even if it is
 > superior. It'll require a bit more discussion.

Its certainly possible to do this just with the CHANGE syntax, you would just have to specify
the column name twice and the type even if those aren't changing, as we discussed with Greg.
Given that, I still think its the right choice to add the new syntax.

It doesn't work right now - for Kudu, CHANGE only supports renaming columns, so specifying
a different type gives you an AnalysisException, specifying both column names as the same
gets a 'column already exists' error back from Kudu, specifying a comment gets dropped silently,
and specifying the Kudu-specific options gets an 'Unsupported option' analysis error, but
all of those things are easily fixable.

At the very least, you're right that this can be implemented using the existing code for CHANGE,
so I should be able to simplify what I've got here.

-- 
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Gerrit-MessageType: comment
Gerrit-Change-Id: Id2e8bd65342b79644a0fdcd925e6f17797e89ad6
Gerrit-PatchSet: 2
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Thomas Tauber-Marshall <tmarshall@cloudera.com>
Gerrit-Reviewer: Matthew Jacobs <mj@cloudera.com>
Gerrit-Reviewer: Thomas Tauber-Marshall <tmarshall@cloudera.com>
Gerrit-HasComments: No

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