COMMENT
COMMENT — define or change the comment of an object
Synopsis
COMMENT ON { AGGREGATEaggregate_name
(aggregate_signature
) | CAST (source_type
AStarget_type
) | COLLATIONobject_name
| COLUMNrelation_name
.column_name
| CONSTRAINTconstraint_name
ONtable_name
| CONSTRAINTconstraint_name
ON DOMAINdomain_name
| CONVERSIONobject_name
| DATABASEobject_name
| DOMAINobject_name
| EXTENSIONobject_name
| EVENT TRIGGERobject_name
| FOREIGN DATA WRAPPERobject_name
| FOREIGN TABLEobject_name
| FUNCTIONfunction_name
( [ [argmode
] [argname
]argtype
[, ...] ] ) | INDEXobject_name
| LARGE OBJECTlarge_object_oid
| MATERIALIZED VIEWobject_name
| OPERATORoperator_name
(left_type
,right_type
) | OPERATOR CLASSobject_name
USINGindex_method
| OPERATOR FAMILYobject_name
USINGindex_method
| POLICYpolicy_name
ONtable_name
| [ PROCEDURAL ] LANGUAGEobject_name
| ROLEobject_name
| RULErule_name
ONtable_name
| SCHEMAobject_name
| SEQUENCEobject_name
| SERVERobject_name
| TABLEobject_name
| TABLESPACEobject_name
| TEXT SEARCH CONFIGURATIONobject_name
| TEXT SEARCH DICTIONARYobject_name
| TEXT SEARCH PARSERobject_name
| TEXT SEARCH TEMPLATEobject_name
| TRANSFORM FORtype_name
LANGUAGElang_name
| TRIGGERtrigger_name
ONtable_name
| TYPEobject_name
| VIEWobject_name
} IS 'text
' whereaggregate_signature
is: * | [argmode
] [argname
]argtype
[ , ... ] | [ [argmode
] [argname
]argtype
[ , ... ] ] ORDER BY [argmode
] [argname
]argtype
[ , ... ]
Description
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, write NULL
in place of the text string. Comments are automatically dropped when their object is dropped.
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. Of course, a superuser can comment on anything.
Comments can be viewed using psql's \d
family of commands. 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
(see Table 9.62).
Parameters
object_name
relation_name
.column_name
aggregate_name
constraint_name
function_name
operator_name
policy_name
rule_name
trigger_name
The name of the object to be commented. Names of tables, aggregates, collations, conversions, domains, foreign tables, functions, indexes, operators, operator classes, operator families, sequences, text search objects, types, and views can be schema-qualified. When commenting on a column,
relation_name
must refer to a table, view, composite type, or foreign table.table_name
domain_name
When creating a comment on a constraint, a trigger, a rule or a policy these parameters specify the name of the table or domain on which that object is defined.
source_type
The name of the source data type of the cast.
target_type
The name of the target data type of the cast.
argmode
The mode of a function or aggregate argument:
IN
,OUT
,INOUT
, orVARIADIC
. If omitted, the default isIN
. Note thatCOMMENT
does not actually pay any attention toOUT
arguments, since only the input arguments are needed to determine the function's identity. So it is sufficient to list theIN
,INOUT
, andVARIADIC
arguments.argname
The name of a function or aggregate argument. Note that
COMMENT
does not actually pay any attention to argument names, since only the argument data types are needed to determine the function's identity.argtype
The data type of a function or aggregate argument.
large_object_oid
The OID of the large object.
left_type
right_type
The data type(s) of the operator's arguments (optionally schema-qualified). Write
NONE
for the missing argument of a prefix or postfix operator.PROCEDURAL
This is a noise word.
type_name
The name of the data type of the transform.
lang_name
The name of the language of the transform.
text
The new comment, written as a string literal; or
NULL
to drop the comment.
Notes
There is presently no security mechanism for viewing comments: any user connected to a database can see all 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. Therefore, don't put security-critical information in comments.
Examples
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;
Some more examples:
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 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 LARGE OBJECT 346344 IS 'Planning document'; 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 int4ops 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 ROLE my_role IS 'Administration group for finance tables'; 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 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';
Compatibility
There is no COMMENT
command in the SQL standard.