1<!-- 2doc/src/sgml/ref/comment.sgml 3PostgreSQL documentation 4--> 5 6<refentry id="sql-comment"> 7 <indexterm zone="sql-comment"> 8 <primary>COMMENT</primary> 9 </indexterm> 10 11 <refmeta> 12 <refentrytitle>COMMENT</refentrytitle> 13 <manvolnum>7</manvolnum> 14 <refmiscinfo>SQL - Language Statements</refmiscinfo> 15 </refmeta> 16 17 <refnamediv> 18 <refname>COMMENT</refname> 19 <refpurpose>define or change the comment of an object</refpurpose> 20 </refnamediv> 21 22 <refsynopsisdiv> 23<synopsis> 24COMMENT ON 25{ 26 ACCESS METHOD <replaceable class="parameter">object_name</replaceable> | 27 AGGREGATE <replaceable class="parameter">aggregate_name</replaceable> ( <replaceable>aggregate_signature</replaceable> ) | 28 CAST (<replaceable>source_type</replaceable> AS <replaceable>target_type</replaceable>) | 29 COLLATION <replaceable class="parameter">object_name</replaceable> | 30 COLUMN <replaceable class="parameter">relation_name</replaceable>.<replaceable class="parameter">column_name</replaceable> | 31 CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> ON <replaceable class="parameter">table_name</replaceable> | 32 CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> ON DOMAIN <replaceable class="parameter">domain_name</replaceable> | 33 CONVERSION <replaceable class="parameter">object_name</replaceable> | 34 DATABASE <replaceable class="parameter">object_name</replaceable> | 35 DOMAIN <replaceable class="parameter">object_name</replaceable> | 36 EXTENSION <replaceable class="parameter">object_name</replaceable> | 37 EVENT TRIGGER <replaceable class="parameter">object_name</replaceable> | 38 FOREIGN DATA WRAPPER <replaceable class="parameter">object_name</replaceable> | 39 FOREIGN TABLE <replaceable class="parameter">object_name</replaceable> | 40 FUNCTION <replaceable class="parameter">function_name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ] | 41 INDEX <replaceable class="parameter">object_name</replaceable> | 42 LARGE OBJECT <replaceable class="parameter">large_object_oid</replaceable> | 43 MATERIALIZED VIEW <replaceable class="parameter">object_name</replaceable> | 44 OPERATOR <replaceable class="parameter">operator_name</replaceable> (<replaceable class="parameter">left_type</replaceable>, <replaceable class="parameter">right_type</replaceable>) | 45 OPERATOR CLASS <replaceable class="parameter">object_name</replaceable> USING <replaceable class="parameter">index_method</replaceable> | 46 OPERATOR FAMILY <replaceable class="parameter">object_name</replaceable> USING <replaceable class="parameter">index_method</replaceable> | 47 POLICY <replaceable class="parameter">policy_name</replaceable> ON <replaceable class="parameter">table_name</replaceable> | 48 [ PROCEDURAL ] LANGUAGE <replaceable class="parameter">object_name</replaceable> | 49 PROCEDURE <replaceable class="parameter">procedure_name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ] | 50 PUBLICATION <replaceable class="parameter">object_name</replaceable> | 51 ROLE <replaceable class="parameter">object_name</replaceable> | 52 ROUTINE <replaceable class="parameter">routine_name</replaceable> [ ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) ] | 53 RULE <replaceable class="parameter">rule_name</replaceable> ON <replaceable class="parameter">table_name</replaceable> | 54 SCHEMA <replaceable class="parameter">object_name</replaceable> | 55 SEQUENCE <replaceable class="parameter">object_name</replaceable> | 56 SERVER <replaceable class="parameter">object_name</replaceable> | 57 STATISTICS <replaceable class="parameter">object_name</replaceable> | 58 SUBSCRIPTION <replaceable class="parameter">object_name</replaceable> | 59 TABLE <replaceable class="parameter">object_name</replaceable> | 60 TABLESPACE <replaceable class="parameter">object_name</replaceable> | 61 TEXT SEARCH CONFIGURATION <replaceable class="parameter">object_name</replaceable> | 62 TEXT SEARCH DICTIONARY <replaceable class="parameter">object_name</replaceable> | 63 TEXT SEARCH PARSER <replaceable class="parameter">object_name</replaceable> | 64 TEXT SEARCH TEMPLATE <replaceable class="parameter">object_name</replaceable> | 65 TRANSFORM FOR <replaceable>type_name</replaceable> LANGUAGE <replaceable>lang_name</replaceable> | 66 TRIGGER <replaceable class="parameter">trigger_name</replaceable> ON <replaceable class="parameter">table_name</replaceable> | 67 TYPE <replaceable class="parameter">object_name</replaceable> | 68 VIEW <replaceable class="parameter">object_name</replaceable> 69} IS '<replaceable class="parameter">text</replaceable>' 70 71<phrase>where <replaceable>aggregate_signature</replaceable> is:</phrase> 72 73* | 74[ <replaceable>argmode</replaceable> ] [ <replaceable>argname</replaceable> ] <replaceable>argtype</replaceable> [ , ... ] | 75[ [ <replaceable>argmode</replaceable> ] [ <replaceable>argname</replaceable> ] <replaceable>argtype</replaceable> [ , ... ] ] ORDER BY [ <replaceable>argmode</replaceable> ] [ <replaceable>argname</replaceable> ] <replaceable>argtype</replaceable> [ , ... ] 76</synopsis> 77 </refsynopsisdiv> 78 79 <refsect1> 80 <title>Description</title> 81 82 <para> 83 <command>COMMENT</command> stores a comment about a database object. 84 </para> 85 86 <para> 87 Only one comment string is stored for each object, so to modify a comment, 88 issue a new <command>COMMENT</command> command for the same object. To remove a 89 comment, write <literal>NULL</literal> in place of the text string. 90 Comments are automatically dropped when their object is dropped. 91 </para> 92 93 <para> 94 For most kinds of object, only the object's owner can set the comment. 95 Roles don't have owners, so the rule for <literal>COMMENT ON ROLE</literal> is 96 that you must be superuser to comment on a superuser role, or have the 97 <literal>CREATEROLE</literal> privilege to comment on non-superuser roles. 98 Likewise, access methods don't have owners either; you must be superuser 99 to comment on an access method. 100 Of course, a superuser can comment on anything. 101 </para> 102 103 <para> 104 Comments can be viewed using <application>psql</application>'s 105 <command>\d</command> family of commands. 106 Other user interfaces to retrieve comments can be built atop 107 the same built-in functions that <application>psql</application> uses, namely 108 <function>obj_description</function>, <function>col_description</function>, 109 and <function>shobj_description</function> 110 (see <xref linkend="functions-info-comment-table"/>). 111 </para> 112 </refsect1> 113 114 <refsect1> 115 <title>Parameters</title> 116 117 <variablelist> 118 <varlistentry> 119 <term><replaceable class="parameter">object_name</replaceable></term> 120 <term><replaceable class="parameter">relation_name</replaceable>.<replaceable>column_name</replaceable></term> 121 <term><replaceable class="parameter">aggregate_name</replaceable></term> 122 <term><replaceable class="parameter">constraint_name</replaceable></term> 123 <term><replaceable class="parameter">function_name</replaceable></term> 124 <term><replaceable class="parameter">operator_name</replaceable></term> 125 <term><replaceable class="parameter">policy_name</replaceable></term> 126 <term><replaceable class="parameter">procedure_name</replaceable></term> 127 <term><replaceable class="parameter">routine_name</replaceable></term> 128 <term><replaceable class="parameter">rule_name</replaceable></term> 129 <term><replaceable class="parameter">trigger_name</replaceable></term> 130 <listitem> 131 <para> 132 The name of the object to be commented. Names of tables, 133 aggregates, collations, conversions, domains, foreign tables, functions, 134 indexes, operators, operator classes, operator families, procedures, routines, sequences, 135 statistics, text search objects, types, and views can be 136 schema-qualified. When commenting on a column, 137 <replaceable class="parameter">relation_name</replaceable> must refer 138 to a table, view, composite type, or foreign table. 139 </para> 140 </listitem> 141 </varlistentry> 142 143 <varlistentry> 144 <term><replaceable class="parameter">table_name</replaceable></term> 145 <term><replaceable class="parameter">domain_name</replaceable></term> 146 <listitem> 147 <para> 148 When creating a comment on a constraint, a trigger, a rule or 149 a policy these parameters specify the name of the table or domain on 150 which that object is defined. 151 </para> 152 </listitem> 153 </varlistentry> 154 155 <varlistentry> 156 <term><replaceable>source_type</replaceable></term> 157 <listitem> 158 <para> 159 The name of the source data type of the cast. 160 </para> 161 </listitem> 162 </varlistentry> 163 164 <varlistentry> 165 <term><replaceable>target_type</replaceable></term> 166 <listitem> 167 <para> 168 The name of the target data type of the cast. 169 </para> 170 </listitem> 171 </varlistentry> 172 173 <varlistentry> 174 <term><replaceable class="parameter">argmode</replaceable></term> 175 <listitem> 176 <para> 177 The mode of a function, procedure, or aggregate 178 argument: <literal>IN</literal>, <literal>OUT</literal>, 179 <literal>INOUT</literal>, or <literal>VARIADIC</literal>. 180 If omitted, the default is <literal>IN</literal>. 181 Note that <command>COMMENT</command> does not actually pay 182 any attention to <literal>OUT</literal> arguments, since only the input 183 arguments are needed to determine the function's identity. 184 So it is sufficient to list the <literal>IN</literal>, <literal>INOUT</literal>, 185 and <literal>VARIADIC</literal> arguments. 186 </para> 187 </listitem> 188 </varlistentry> 189 190 <varlistentry> 191 <term><replaceable class="parameter">argname</replaceable></term> 192 <listitem> 193 <para> 194 The name of a function, procedure, or aggregate argument. 195 Note that <command>COMMENT</command> does not actually pay 196 any attention to argument names, since only the argument data 197 types are needed to determine the function's identity. 198 </para> 199 </listitem> 200 </varlistentry> 201 202 <varlistentry> 203 <term><replaceable class="parameter">argtype</replaceable></term> 204 <listitem> 205 <para> 206 The data type of a function, procedure, or aggregate argument. 207 </para> 208 </listitem> 209 </varlistentry> 210 211 <varlistentry> 212 <term><replaceable class="parameter">large_object_oid</replaceable></term> 213 <listitem> 214 <para> 215 The OID of the large object. 216 </para> 217 </listitem> 218 </varlistentry> 219 220 <varlistentry> 221 <term><replaceable class="parameter">left_type</replaceable></term> 222 <term><replaceable class="parameter">right_type</replaceable></term> 223 <listitem> 224 <para> 225 The data type(s) of the operator's arguments (optionally 226 schema-qualified). Write <literal>NONE</literal> for the missing argument 227 of a prefix or postfix operator. 228 </para> 229 </listitem> 230 </varlistentry> 231 232 <varlistentry> 233 <term><literal>PROCEDURAL</literal></term> 234 <listitem> 235 <para> 236 This is a noise word. 237 </para> 238 </listitem> 239 </varlistentry> 240 241 <varlistentry> 242 <term><replaceable>type_name</replaceable></term> 243 244 <listitem> 245 <para> 246 The name of the data type of the transform. 247 </para> 248 </listitem> 249 </varlistentry> 250 251 <varlistentry> 252 <term><replaceable>lang_name</replaceable></term> 253 254 <listitem> 255 <para> 256 The name of the language of the transform. 257 </para> 258 </listitem> 259 </varlistentry> 260 261 <varlistentry> 262 <term><replaceable class="parameter">text</replaceable></term> 263 <listitem> 264 <para> 265 The new comment, written as a string literal; or <literal>NULL</literal> 266 to drop the comment. 267 </para> 268 </listitem> 269 </varlistentry> 270 271 </variablelist> 272 </refsect1> 273 274 <refsect1> 275 <title>Notes</title> 276 277 <para> 278 There is presently no security mechanism for viewing comments: any user 279 connected to a database can see all the comments for objects in 280 that database. For shared objects such as 281 databases, roles, and tablespaces, comments are stored globally so any 282 user connected to any database in the cluster can see all the comments 283 for shared objects. Therefore, don't put security-critical 284 information in comments. 285 </para> 286 </refsect1> 287 288 <refsect1> 289 <title>Examples</title> 290 291 <para> 292 Attach a comment to the table <literal>mytable</literal>: 293 294<programlisting> 295COMMENT ON TABLE mytable IS 'This is my table.'; 296</programlisting> 297 298 Remove it again: 299 300<programlisting> 301COMMENT ON TABLE mytable IS NULL; 302</programlisting> 303 </para> 304 305 <para> 306 Some more examples: 307 308<programlisting> 309COMMENT ON ACCESS METHOD gin IS 'GIN index access method'; 310COMMENT ON AGGREGATE my_aggregate (double precision) IS 'Computes sample variance'; 311COMMENT ON CAST (text AS int4) IS 'Allow casts from text to int4'; 312COMMENT ON COLLATION "fr_CA" IS 'Canadian French'; 313COMMENT ON COLUMN my_table.my_column IS 'Employee ID number'; 314COMMENT ON CONVERSION my_conv IS 'Conversion to UTF8'; 315COMMENT ON CONSTRAINT bar_col_cons ON bar IS 'Constrains column col'; 316COMMENT ON CONSTRAINT dom_col_constr ON DOMAIN dom IS 'Constrains col of domain'; 317COMMENT ON DATABASE my_database IS 'Development Database'; 318COMMENT ON DOMAIN my_domain IS 'Email Address Domain'; 319COMMENT ON EVENT TRIGGER abort_ddl IS 'Aborts all DDL commands'; 320COMMENT ON EXTENSION hstore IS 'implements the hstore data type'; 321COMMENT ON FOREIGN DATA WRAPPER mywrapper IS 'my foreign data wrapper'; 322COMMENT ON FOREIGN TABLE my_foreign_table IS 'Employee Information in other database'; 323COMMENT ON FUNCTION my_function (timestamp) IS 'Returns Roman Numeral'; 324COMMENT ON INDEX my_index IS 'Enforces uniqueness on employee ID'; 325COMMENT ON LANGUAGE plpython IS 'Python support for stored procedures'; 326COMMENT ON LARGE OBJECT 346344 IS 'Planning document'; 327COMMENT ON MATERIALIZED VIEW my_matview IS 'Summary of order history'; 328COMMENT ON OPERATOR ^ (text, text) IS 'Performs intersection of two texts'; 329COMMENT ON OPERATOR - (NONE, integer) IS 'Unary minus'; 330COMMENT ON OPERATOR CLASS int4ops USING btree IS '4 byte integer operators for btrees'; 331COMMENT ON OPERATOR FAMILY integer_ops USING btree IS 'all integer operators for btrees'; 332COMMENT ON POLICY my_policy ON mytable IS 'Filter rows by users'; 333COMMENT ON PROCEDURE my_proc (integer, integer) IS 'Runs a report'; 334COMMENT ON PUBLICATION alltables IS 'Publishes all operations on all tables'; 335COMMENT ON ROLE my_role IS 'Administration group for finance tables'; 336COMMENT ON ROUTINE my_routine (integer, integer) IS 'Runs a routine (which is a function or procedure)'; 337COMMENT ON RULE my_rule ON my_table IS 'Logs updates of employee records'; 338COMMENT ON SCHEMA my_schema IS 'Departmental data'; 339COMMENT ON SEQUENCE my_sequence IS 'Used to generate primary keys'; 340COMMENT ON SERVER myserver IS 'my foreign server'; 341COMMENT ON STATISTICS my_statistics IS 'Improves planner row estimations'; 342COMMENT ON SUBSCRIPTION alltables IS 'Subscription for all operations on all tables'; 343COMMENT ON TABLE my_schema.my_table IS 'Employee Information'; 344COMMENT ON TABLESPACE my_tablespace IS 'Tablespace for indexes'; 345COMMENT ON TEXT SEARCH CONFIGURATION my_config IS 'Special word filtering'; 346COMMENT ON TEXT SEARCH DICTIONARY swedish IS 'Snowball stemmer for Swedish language'; 347COMMENT ON TEXT SEARCH PARSER my_parser IS 'Splits text into words'; 348COMMENT ON TEXT SEARCH TEMPLATE snowball IS 'Snowball stemmer'; 349COMMENT ON TRANSFORM FOR hstore LANGUAGE plpythonu IS 'Transform between hstore and Python dict'; 350COMMENT ON TRIGGER my_trigger ON my_table IS 'Used for RI'; 351COMMENT ON TYPE complex IS 'Complex number data type'; 352COMMENT ON VIEW my_view IS 'View of departmental costs'; 353</programlisting></para> 354 </refsect1> 355 356 <refsect1> 357 <title>Compatibility</title> 358 359 <para> 360 There is no <command>COMMENT</command> command in the SQL standard. 361 </para> 362 </refsect1> 363</refentry> 364