dianfu commented on a change in pull request #8057: [FLINK-12028][table] Add 
`addColumns`,`renameColumns`, `dropColumns` …
URL: https://github.com/apache/flink/pull/8057#discussion_r269882661
 
 

 ##########
 File path: 
flink-table/flink-table-api-java/src/main/java/org/apache/flink/table/api/Table.java
 ##########
 @@ -879,4 +879,118 @@
         * @return An OverWindowedTable to specify the aggregations.
         */
        OverWindowedTable window(OverWindow... overWindows);
+
+       /**
+        * Performs a field add operation. Similar to an SQL SELECT statement. 
The field expressions
+        * can contain complex expressions, but can not contain aggregations. 
It will throw an exception
+        * if the added fields already exist.
+        *
+        * <p>Example:
+        * <pre>
+        * {@code
+        *   tab.addColumns("a + 1 as a1, concat(b, 'sunny') as b1")
+        * }
+        * </pre>
+        */
+       Table addColumns(String fields);
+
+       /**
+        * Performs a field add operation. Similar to an SQL SELECT statement. 
The field expressions
+        * can contain complex expressions, but can not contain aggregations. 
It will throw an exception
+        * if the added fields already exist.
+        *
+        * <p>Scala Example:
+        *
+        * <pre>
+        * {@code
+        *   tab.addColumns('a + 1 as 'a1, concat('b, "sunny") as 'b1)
+        * }
+        * </pre>
+        */
+       Table addColumns(Expression... fields);
+
+       /**
+        * Performs a field add operation. Similar to an SQL SELECT statement. 
The field expressions
+        * can contain complex expressions, but can not contain aggregations. 
Existing fields will be
+        * replaced if {@code replaceIfExist} is true. If the added fields have 
duplicate field name,
+        * then the last one is valid.
+        *
+        * <p>Example:
+        * <pre>
+        * {@code
+        *   tab.addColumns(true, "a + 1 as a1, concat(b, 'sunny') as b1")
+        * }
+        * </pre>
+        */
+       Table addColumns(boolean replaceIfExist, String fields);
+
+       /**
+        * Performs a field add operation. Similar to an SQL SELECT statement. 
The field expressions
+        * can contain complex expressions, but can not contain aggregations. 
Existing fields will be
+        * replaced if {@code replaceIfExist} is true. If the added fields have 
duplicate field name,
+        * then the last one is valid.
+        *
+        * <p>Scala Example:
+        * <pre>
+        * {@code
+        *   tab.addColumns(true, 'a + 1 as 'a1, concat('b, "sunny") as 'b1)
+        * }
+        * </pre>
+        */
+       Table addColumns(boolean replaceIfExist, Expression... fields);
+
+       /**
+        * Performs a field rename operation. Similar to an field alias 
statement. The field expressions
+        * should be alias expressions, and only the existing fields can be 
renamed.
+        *
+        * <p>Example:
+        *
+        * <pre>
+        * {@code
+        *   tab.renameColumns("a as a1, b as b1")
+        * }
+        * </pre>
+        */
+       Table renameColumns(String fields);
+
+       /**
+        * Performs a field rename operation. Similar to an field alias 
statement. The field expressions
+        * should be alias expressions, and only the existing fields can be 
renamed.
+        *
+        * <p>Scala Example:
+        *
+        * <pre>
+        * {@code
+        *   tab.renameColumns('a as 'a1, 'b as 'b1)
+        * }
+        * </pre>
+        */
+       Table renameColumns(Expression... fields);
+
+       /**
+        * Performs a field drop operation. The field expressions
+        * should be an field reference expressions, and only existing fields 
can be dropped.
 
 Review comment:
   remove "an"

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