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commit efd2478ed3c5f54ec5a1c486e7f4c657ca6addac
Author: Alex Rodoni <arod...@cloudera.com>
AuthorDate: Mon Feb 4 16:51:43 2019 -0800
IMPALA-8104: IF NOT EXISTS to ALTER TABLE ADD COLUMN(S)
Change-Id: Ieec5f99d868eee05dbf2cecff41dd57561360333
Reviewed-on: http://gerrit.cloudera.org:8080/12361
Reviewed-by: Fredy Wijaya <fwij...@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenk...@cloudera.com>
---
docs/topics/impala_alter_table.xml | 44 ++++++++++++++++----------------------
1 file changed, 19 insertions(+), 25 deletions(-)
diff --git a/docs/topics/impala_alter_table.xml
b/docs/topics/impala_alter_table.xml
index 412aff0..8529a9c 100644
--- a/docs/topics/impala_alter_table.xml
+++ b/docs/topics/impala_alter_table.xml
@@ -46,11 +46,8 @@ under the License.
<conbody>
- <p>
- <indexterm audience="hidden">ALTER TABLE statement</indexterm>
- The <codeph>ALTER TABLE</codeph> statement changes the structure or
properties of an
- existing Impala table.
- </p>
+ <p> The <codeph>ALTER TABLE</codeph> statement changes the structure or
+ properties of an existing Impala table. </p>
<p>
In Impala, this is primarily a logical operation that updates the table
metadata in the
@@ -66,12 +63,13 @@ under the License.
<codeblock>ALTER TABLE
[<varname>old_db_name</varname>.]<varname>old_table_name</varname> RENAME TO
[<varname>new_db_name</varname>.]<varname>new_table_name</varname>
-ALTER TABLE <varname>name</varname> ADD COLUMNS (<varname>col_spec</varname>[,
<varname>col_spec</varname> ...])
+ALTER TABLE <varname>name</varname> ADD [IF NOT EXISTS] COLUMNS
(<varname>col_spec</varname>[, <varname>col_spec</varname> ...])
+ALTER TABLE <varname>name</varname> REPLACE COLUMNS
(<varname>col_spec</varname>[, <varname>col_spec</varname> ...])
+
+ALTER TABLE <varname>name</varname> ADD COLUMN [IF NOT EXISTS]
<varname>col_spec</varname>
ALTER TABLE <varname>name</varname> DROP [COLUMN]
<varname>column_name</varname>
ALTER TABLE <varname>name</varname> CHANGE <varname>column_name</varname>
<varname>col_spec</varname>
-ALTER TABLE <varname>name</varname> REPLACE COLUMNS
(<varname>col_spec</varname>[, <varname>col_spec</varname> ...])
-
<ph rev="3.1 IMPALA-6988">ALTER TABLE <varname>name</varname> SET OWNER USER
<varname>user_name</varname>
ALTER TABLE <varname>name</varname> SET OWNER ROLE <varname>role_name</varname>
</ph>
@@ -546,23 +544,19 @@ ALTER TABLE <varname>table_name</varname> SET
SERDEPROPERTIES ('<varname>key1</v
<p>
<b>To reorganize columns for a table:</b>
</p>
-
-<codeblock>ALTER TABLE <varname>table_name</varname> ADD COLUMNS
(<varname>column_defs</varname>);
-ALTER TABLE <varname>table_name</varname> REPLACE COLUMNS
(<varname>column_defs</varname>);
-ALTER TABLE <varname>table_name</varname> CHANGE
<varname>column_name</varname> <varname>new_name</varname>
<varname>new_type</varname>;
-ALTER TABLE <varname>table_name</varname> DROP
<varname>column_name</varname>;</codeblock>
-
- <p>
- The <varname>column_spec</varname> is the same as in the <codeph>CREATE
TABLE</codeph>
- statement: the column name, then its data type, then an optional
comment. You can add
- multiple columns at a time. The parentheses are required whether you add
a single column
- or multiple columns. When you replace columns, all the original column
definitions are
- discarded. You might use this technique if you receive a new set of data
files with
- different data types or columns in a different order. (The data files
are retained, so if
- the new columns are incompatible with the old ones, use <codeph>INSERT
OVERWRITE</codeph>
- or <codeph>LOAD DATA OVERWRITE</codeph> to replace all the data before
issuing any further
- queries.)
- </p>
+ <p>You can add multiple columns at a time using the <codeph>ALTER
+ TABLE</codeph> statement. If you specify the <codeph>IF NOT
+ EXISTS</codeph> clause, Impala silently ignores the
<codeph>ADD</codeph>
+ request and does not return an error if a column with the same name
exists
+ in the table.</p>
+ <p>When you replace columns, all the original column definitions are
+ discarded. </p>
+ <p>You might use these statements if you receive a new set of data files
+ with different data types or columns in a different order. The data files
+ are retained, so if the new columns are incompatible with the old ones,
+ use <codeph>INSERT OVERWRITE</codeph> or <codeph>LOAD DATA
+ OVERWRITE</codeph> to replace all the data before issuing any further
+ queries.</p>
<p rev="">
For example, here is how you might add columns to an existing table. The
first
