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COMMENT

COMMENT — define or change the comment of an object

Synopsis

COMMENT ON{  ACCESS METHODobject_name |  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 |  PROCEDUREprocedure_name [ ( [ [argmode ] [argname ]argtype [, ...] ] ) ] |  PUBLICATIONobject_name |  ROLEobject_name |  ROUTINEroutine_name [ ( [ [argmode ] [argname ]argtype [, ...] ] ) ] |  RULErule_name ONtable_name |  SCHEMAobject_name |  SEQUENCEobject_name |  SERVERobject_name |  STATISTICSobject_name |  SUBSCRIPTIONobject_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 {string_literal | NULL }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 newCOMMENT command for the same object. To remove a comment, writeNULL in place of the text string. Comments are automatically dropped when their object is dropped.

ASHARE 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 forCOMMENT ON ROLE is that you must be superuser to comment on a superuser role, or have theCREATEROLE 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 usingpsql's\d family of commands. Other user interfaces to retrieve comments can be built atop the same built-in functions thatpsql uses, namelyobj_description,col_description, andshobj_description (seeTable 9.73).

Parameters

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 tablemytable:

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 noCOMMENT command in the SQL standard.