Matthew Jacobs has posted comments on this change.

Change subject: IMPALA-4622: Add ALTER COLUMN statement.
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Patch Set 1:

(2 comments)

http://gerrit.cloudera.org:8080/#/c/6955/1//COMMIT_MSG
Commit Message:

Line 8: 
Need to explain why this diverges from ALTER TABLE CHANGE, since that syntax 
exists and appears to overlap.

>From the doc, it says:
ALTER TABLE name CHANGE column_name new_name new_type

However, this change led me to look at the code, and according to the parser it 
looks the syntax is actually:

ALTER TABLE name CHANGE column_name new_name column_def

column_def ::=
  ident_or_default:col_name type_def:type column_options_map:options
  {: RESULT = new ColumnDef(col_name, type, options); :}
  | ident_or_default:col_name type_def:type
  {: RESULT = new ColumnDef(col_name, type); :}
  ;


So then the column def options would already be possible to set with that 
syntax.

While I much much prefer this syntax you've added here, we need to re-evaluate 
if it makes sense to add it given this new information.


http://gerrit.cloudera.org:8080/#/c/6955/1/common/thrift/JniCatalog.thrift
File common/thrift/JniCatalog.thrift:

Line 74:   ALTER_COLUMN,
internally can we re-use change_column?


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Gerrit-MessageType: comment
Gerrit-Change-Id: Id2e8bd65342b79644a0fdcd925e6f17797e89ad6
Gerrit-PatchSet: 1
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Thomas Tauber-Marshall <[email protected]>
Gerrit-Reviewer: Matthew Jacobs <[email protected]>
Gerrit-HasComments: Yes

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