NAME

       COMMENT - define or change the comment of an object

SYNOPSIS

       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 |
         EXTENSION object_name |
         EVENT TRIGGER object_name |
         FOREIGN DATA WRAPPER object_name |
         FOREIGN TABLE object_name |
         FUNCTION function_name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ] |
         INDEX object_name |
         LARGE OBJECT large_object_oid |
         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 [, ...] ] ) ] |
         PUBLICATION 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 |
         SUBSCRIPTION 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 [ , ... ]

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.

       A SHARE UPDATE EXCLUSIVE lock is acquired 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.

       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 9.73).

PARAMETERS

       object_name
       relation_name.column_name
       aggregate_name
       constraint_name
       function_name
       operator_name
       policy_name
       procedure_name
       routine_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, procedures, routines, sequences, statistics, 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, procedure, or aggregate argument: IN, OUT, INOUT, or VARIADIC.
           If omitted, the default is IN. Note that COMMENT does not actually pay any attention
           to OUT arguments, since only the input arguments are needed to determine the
           function's identity. So it is sufficient to list the IN, INOUT, and VARIADIC
           arguments.

       argname
           The name of a function, procedure, 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, procedure, 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.

       string_literal
           The new comment contents, written as a string literal.

       NULL
           Write 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 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 abort_ddl IS 'Aborts all DDL 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 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 PROCEDURE my_proc (integer, integer) IS 'Runs a report';
           COMMENT ON PUBLICATION alltables IS 'Publishes all operations on all tables';
           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 SUBSCRIPTION alltables IS 'Subscription for all operations on all tables';
           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.