Thomas Tauber-Marshall a306096e56 IMPALA-4622: Add ALTER COLUMN statement. ...

Kudu recently added the ability to alter a column's default value
and storage attributes (KUDU-861). This patch adds the ability to
modify these from Impala using ALTER.

It also supports altering a column's comment for non-Kudu tables.

It does not support setting a column to be a primary key or
changing a column's nullability, because those are not supported on
the Kudu side yet.

Syntax:
ALTER TABLE <table> ALTER [COLUMN] <column>
  SET <attr> <value> [<attr> <value> [<attr> <value>...]]
where <attr> is one of:
  - DEFAULT, BLOCK_SIZE, ENCODING, COMPRESSION (Kudu tables)
  - COMMENT (non-Kudu tables)
ALTER TABLE <table> ALTER [COLUMN] <column> DROP DEFAULT

This is similar to the existing CHANGE statement:
ALTER TABLE <table> CHANGE <column> <new_col_name> <type>
  [COMMENT <comment>]
but the new syntax is more natural for setting column properties
when the column name and type are not being changed. Both ALTER
COLUMN and CHANGE COLUMN operations use AlterTableAlterColStmt and
are sent to the catalog as ALTER_COLUMN operations.

Testing:
- Added FE tests to ParserTest and AnalyzeDDLTest
- Added EE tests to test_kudu.py

Change-Id: Id2e8bd65342b79644a0fdcd925e6f17797e89ad6
Reviewed-on: http://gerrit.cloudera.org:8080/6955
Reviewed-by: Thomas Tauber-Marshall <tmarshall@cloudera.com>
Tested-by: Impala Public Jenkins

2017-06-22 19:08:59 +00:00

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