COMMENT ON

You can use the COMMENT ON command to add comments on tables or columns in RisingWave. Comments are stored as metadata of tables or columns.

If you want to remove an existing comment on a table or column, rewrite the current comment with NULL.

Syntax

COMMENT ON <object_type> <relation_name>.<object_name> IS <comment>

Parameters

Parameter	Notes
object_type	Type of the object that you want to add comments to. Allowed values: TABLE, COLUMN.
relation_name.object_name	Name of the object that you want to add comments to. For columns, you also need to specify the table name.
comment	Comment that you want to add.

Examples

Add a comment on a table:

COMMENT ON TABLE t1 IS 'table to store traffic data';

Add a comment to a column:

COMMENT ON COLUMN t1.v1 IS 'column for the duration of the trip';

Remove the comment on a table:

COMMENT ON table t1 IS NULL;

After a comment is added to a table or column, you can display it in these ways:

1. Using the rw_description table:

SELECT * FROM rw_description;
------
 objoid | classoid | objsubid |             description             
--------+----------+----------+-------------------------------------
   1001 |       41 |          | table to store traffic data
   1001 |       41 |        1 | column for the duration of the trip
   1001 |       41 |        2 | 
   1001 |       41 |        0 | 

2. Using the SHOW COLUMNS or DESCRIBE command:

SHOW COLUMNS FROM t1;

DESCRIBE t1;

Related topics

• DESCRIBE