Defines or changes the comment of an object.
COMMENT ON
{ ACCESS METHOD <object_name> |
AGGREGATE <aggregate_name> (<aggregate_signature>) |
CAST (<source_type> AS <target_type>) |
COLLATION <object_name>
COLUMN <relation_name>.<column_name> |
CONSTRAINT <constraint_name> ON <table_name> |
CONSTRAINT <constraint_name> ON DOMAIN <domain_name> |
CONVERSION <object_name> |
DATABASE <object_name> |
DOMAIN <object_name> |
EVENT TRIGGER <object_name> |
EXTENSION <object_name> |
FOREIGN DATA WRAPPER <object_name> |
FOREIGN TABLE <object_name> |
FUNCTION <function_name> [([[<argmode>] [<argname>] <argtype> [, ...]])] |
INDEX <object_name> |
MATERIALIZED VIEW <object_name> |
OPERATOR <operator_name> (<left_type>, <right_type>) |
OPERATOR CLASS <object_name> USING <index_method> |
OPERATOR FAMILY <object_name> USING <index_method> |
POLICY <policy_name> ON <table_name> |
[PROCEDURAL] LANGUAGE <object_name> |
PROCEDURE <procedure_name> [([[<argmode>] [<argname>] <argtype> [, ...]])] |
RESOURCE GROUP <object_name> |
RESOURCE QUEUE <object_name> |
ROLE <object_name |
ROUTINE <routine_name> [([[<argmode>] [<argname>] <argtype> [, ...]])] |
RULE <rule_name> ON <table_name> |
SCHEMA <object_name> |
SEQUENCE <object_name> |
SERVER <object_name> |
STATISTICS <object_name> |
TABLE <object_name> |
TABLESPACE <object_name> |
TEXT SEARCH CONFIGURATION <object_name> |
TEXT SEARCH DICTIONARY <object_name> |
TEXT SEARCH PARSER <object_name> |
TEXT SEARCH TEMPLATE <object_name> |
TRANSFORM FOR <type_name> LANGUAGE <lang_name> |
TRIGGER <trigger_name> ON <table_name> |
TYPE <object_name> |
VIEW <object_name>
} IS { <string_literal> | NULL }
where <aggregate_signature> is:
* |
[ <argmode> ] [ <argname> ] <argtype> [ , ... ] |
[ [ <argmode> ] [ <argname> ] <argtype> [ , ... ] ] ORDER BY [ <argmode> ] [ <argname> ] <argtype> [ , ... ]
COMMENT stores a comment about a database object. Only one comment string is stored for each object, so to modify a comment, issue a new COMMENT command for the same object. To remove a comment, specify NULL in place of the text string. Comments are automatically dropped when the object is dropped.
Database acquires a SHARE UPDATE EXCLUSIVE lock on the object to be commented.
For most kinds of object, only the object's owner can set the comment. Roles don't have owners, so the rule for COMMENT ON ROLE is that you must be superuser to comment on a superuser role, or have the CREATEROLE privilege to comment on non-superuser roles. Likewise, access methods don't have owners either; you must be superuser to comment on an access method. Of course, a superuser can comment on anything.
You can view comments using the psql meta-commands \dd, \d+, and \l+. Other user interfaces to retrieve comments can be built atop the same built-in functions that psql uses, namely obj_description(), col_description(), and shobj_description().
Note!
Database does not support triggers.
There is presently no security mechanism for viewing comments: any user connected to a database can see all of the comments for objects in that database. For shared objects such as databases, roles, and tablespaces, comments are stored globally so any user connected to any database in the cluster can see all the comments for shared objects.
Caution! Do not put security-critical information in comments.
Attach a comment to the table mytable:
COMMENT ON TABLE mytable IS 'This is my table.';Remove it again:
COMMENT ON TABLE mytable IS NULL;More examples:
COMMENT ON ACCESS METHOD gin IS 'GIN index access method';
COMMENT ON AGGREGATE my_aggregate (double precision) IS 'Computes sample variance';
COMMENT ON CAST (text AS int4) IS 'Allow casts from text to int4';
COMMENT ON COLLATION "fr_CA" IS 'Canadian French';
COMMENT ON COLUMN my_table.my_column IS 'Employee ID number';
COMMENT ON CONVERSION my_conv IS 'Conversion to UTF8';
COMMENT ON CONSTRAINT bar_col_cons ON bar IS 'Constrains column col';
COMMENT ON CONSTRAINT dom_col_constr ON DOMAIN dom IS 'Constrains col of domain';
COMMENT ON DATABASE my_database IS 'Development Database';
COMMENT ON DOMAIN my_domain IS 'Email Address Domain';
COMMENT ON EVENT TRIGGER cancel_ddl IS 'Cancels all DLL commands';
COMMENT ON EXTENSION hstore IS 'implements the hstore data type';
COMMENT ON FOREIGN DATA WRAPPER mywrapper IS 'my foreign data wrapper';
COMMENT ON FOREIGN TABLE my_foreign_table IS 'Employee Information in other database';
COMMENT ON FUNCTION my_function (timestamp) IS 'Returns Roman Numeral';
COMMENT ON INDEX my_index IS 'Enforces uniqueness on employee ID';
COMMENT ON LANGUAGE plpython IS 'Python support for stored procedures';
COMMENT ON MATERIALIZED VIEW my_matview IS 'Summary of order history';
COMMENT ON OPERATOR ^ (text, text) IS 'Performs intersection of two texts';
COMMENT ON OPERATOR - (NONE, integer) IS 'Unary minus';
COMMENT ON OPERATOR CLASS int4_ops USING btree IS '4 byte integer operators for btrees';
COMMENT ON OPERATOR FAMILY integer_ops USING btree IS 'all integer operators for btrees';
COMMENT ON POLICY my_policy ON mytable IS 'Filter rows by users';
COMMENT ON PROCEDURE my_proc (integer, integer) IS 'Runs a report';
COMMENT ON ROLE my_role IS 'Administration group for finance tables';
COMMENT ON ROUTINE my_routine (integer, integer) IS 'Runs a routine (which is a function or procedure)';
COMMENT ON RULE my_rule ON my_table IS 'Logs updates of employee records';
COMMENT ON SCHEMA my_schema IS 'Departmental data';
COMMENT ON SEQUENCE my_sequence IS 'Used to generate primary keys';
COMMENT ON SERVER myserver IS 'my foreign server';
COMMENT ON STATISTICS my_statistics IS 'Improves planner row estimations';
COMMENT ON TABLE my_schema.my_table IS 'Employee Information';
COMMENT ON TABLESPACE my_tablespace IS 'Tablespace for indexes';
COMMENT ON TEXT SEARCH CONFIGURATION my_config IS 'Special word filtering';
COMMENT ON TEXT SEARCH DICTIONARY swedish IS 'Snowball stemmer for Swedish language';
COMMENT ON TEXT SEARCH PARSER my_parser IS 'Splits text into words';
COMMENT ON TEXT SEARCH TEMPLATE snowball IS 'Snowball stemmer';
COMMENT ON TRANSFORM FOR hstore LANGUAGE plpythonu IS 'Transform between hstore and Python dict';
COMMENT ON TRIGGER my_trigger ON my_table IS 'Used for RI';
COMMENT ON TYPE complex IS 'Complex number data type';
COMMENT ON VIEW my_view IS 'View of departmental costs';There is no COMMENT command in the SQL standard.