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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>COMMENT</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="sql-cluster.html" title="CLUSTER" /><link rel="next" href="sql-commit.html" title="COMMIT" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">COMMENT</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-cluster.html" title="CLUSTER">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><th width="60%" align="center">SQL Commands</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 11.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="sql-commit.html" title="COMMIT">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="SQL-COMMENT"><div class="titlepage"></div><a id="id-1.9.3.52.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">COMMENT</span></h2><p>COMMENT — define or change the comment of an object</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">
COMMENT ON
{
ACCESS METHOD <em class="replaceable"><code>object_name</code></em> |
AGGREGATE <em class="replaceable"><code>aggregate_name</code></em> ( <em class="replaceable"><code>aggregate_signature</code></em> ) |
CAST (<em class="replaceable"><code>source_type</code></em> AS <em class="replaceable"><code>target_type</code></em>) |
COLLATION <em class="replaceable"><code>object_name</code></em> |
COLUMN <em class="replaceable"><code>relation_name</code></em>.<em class="replaceable"><code>column_name</code></em> |
CONSTRAINT <em class="replaceable"><code>constraint_name</code></em> ON <em class="replaceable"><code>table_name</code></em> |
CONSTRAINT <em class="replaceable"><code>constraint_name</code></em> ON DOMAIN <em class="replaceable"><code>domain_name</code></em> |
CONVERSION <em class="replaceable"><code>object_name</code></em> |
DATABASE <em class="replaceable"><code>object_name</code></em> |
DOMAIN <em class="replaceable"><code>object_name</code></em> |
EXTENSION <em class="replaceable"><code>object_name</code></em> |
EVENT TRIGGER <em class="replaceable"><code>object_name</code></em> |
FOREIGN DATA WRAPPER <em class="replaceable"><code>object_name</code></em> |
FOREIGN TABLE <em class="replaceable"><code>object_name</code></em> |
FUNCTION <em class="replaceable"><code>function_name</code></em> [ ( [ [ <em class="replaceable"><code>argmode</code></em> ] [ <em class="replaceable"><code>argname</code></em> ] <em class="replaceable"><code>argtype</code></em> [, ...] ] ) ] |
INDEX <em class="replaceable"><code>object_name</code></em> |
LARGE OBJECT <em class="replaceable"><code>large_object_oid</code></em> |
MATERIALIZED VIEW <em class="replaceable"><code>object_name</code></em> |
OPERATOR <em class="replaceable"><code>operator_name</code></em> (<em class="replaceable"><code>left_type</code></em>, <em class="replaceable"><code>right_type</code></em>) |
OPERATOR CLASS <em class="replaceable"><code>object_name</code></em> USING <em class="replaceable"><code>index_method</code></em> |
OPERATOR FAMILY <em class="replaceable"><code>object_name</code></em> USING <em class="replaceable"><code>index_method</code></em> |
POLICY <em class="replaceable"><code>policy_name</code></em> ON <em class="replaceable"><code>table_name</code></em> |
[ PROCEDURAL ] LANGUAGE <em class="replaceable"><code>object_name</code></em> |
PROCEDURE <em class="replaceable"><code>procedure_name</code></em> [ ( [ [ <em class="replaceable"><code>argmode</code></em> ] [ <em class="replaceable"><code>argname</code></em> ] <em class="replaceable"><code>argtype</code></em> [, ...] ] ) ] |
PUBLICATION <em class="replaceable"><code>object_name</code></em> |
ROLE <em class="replaceable"><code>object_name</code></em> |
ROUTINE <em class="replaceable"><code>routine_name</code></em> [ ( [ [ <em class="replaceable"><code>argmode</code></em> ] [ <em class="replaceable"><code>argname</code></em> ] <em class="replaceable"><code>argtype</code></em> [, ...] ] ) ] |
RULE <em class="replaceable"><code>rule_name</code></em> ON <em class="replaceable"><code>table_name</code></em> |
SCHEMA <em class="replaceable"><code>object_name</code></em> |
SEQUENCE <em class="replaceable"><code>object_name</code></em> |
SERVER <em class="replaceable"><code>object_name</code></em> |
STATISTICS <em class="replaceable"><code>object_name</code></em> |
SUBSCRIPTION <em class="replaceable"><code>object_name</code></em> |
TABLE <em class="replaceable"><code>object_name</code></em> |
TABLESPACE <em class="replaceable"><code>object_name</code></em> |
TEXT SEARCH CONFIGURATION <em class="replaceable"><code>object_name</code></em> |
TEXT SEARCH DICTIONARY <em class="replaceable"><code>object_name</code></em> |
TEXT SEARCH PARSER <em class="replaceable"><code>object_name</code></em> |
TEXT SEARCH TEMPLATE <em class="replaceable"><code>object_name</code></em> |
TRANSFORM FOR <em class="replaceable"><code>type_name</code></em> LANGUAGE <em class="replaceable"><code>lang_name</code></em> |
TRIGGER <em class="replaceable"><code>trigger_name</code></em> ON <em class="replaceable"><code>table_name</code></em> |
TYPE <em class="replaceable"><code>object_name</code></em> |
VIEW <em class="replaceable"><code>object_name</code></em>
} IS '<em class="replaceable"><code>text</code></em>'
<span class="phrase">where <em class="replaceable"><code>aggregate_signature</code></em> is:</span>
* |
[ <em class="replaceable"><code>argmode</code></em> ] [ <em class="replaceable"><code>argname</code></em> ] <em class="replaceable"><code>argtype</code></em> [ , ... ] |
[ [ <em class="replaceable"><code>argmode</code></em> ] [ <em class="replaceable"><code>argname</code></em> ] <em class="replaceable"><code>argtype</code></em> [ , ... ] ] ORDER BY [ <em class="replaceable"><code>argmode</code></em> ] [ <em class="replaceable"><code>argname</code></em> ] <em class="replaceable"><code>argtype</code></em> [ , ... ]
</pre></div><div class="refsect1" id="id-1.9.3.52.5"><h2>Description</h2><p>
<code class="command">COMMENT</code> stores a comment about a database object.
</p><p>
Only one comment string is stored for each object, so to modify a comment,
issue a new <code class="command">COMMENT</code> command for the same object. To remove a
comment, write <code class="literal">NULL</code> in place of the text string.
Comments are automatically dropped when their object is dropped.
</p><p>
For most kinds of object, only the object's owner can set the comment.
Roles don't have owners, so the rule for <code class="literal">COMMENT ON ROLE</code> is
that you must be superuser to comment on a superuser role, or have the
<code class="literal">CREATEROLE</code> 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.
</p><p>
Comments can be viewed using <span class="application">psql</span>'s
<code class="command">\d</code> family of commands.
Other user interfaces to retrieve comments can be built atop
the same built-in functions that <span class="application">psql</span> uses, namely
<code class="function">obj_description</code>, <code class="function">col_description</code>,
and <code class="function">shobj_description</code>
(see <a class="xref" href="functions-info.html#FUNCTIONS-INFO-COMMENT-TABLE" title="Table 9.68. Comment Information Functions">Table 9.68</a>).
</p></div><div class="refsect1" id="id-1.9.3.52.6"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="replaceable"><code>object_name</code></em><br /></span><span class="term"><em class="replaceable"><code>relation_name</code></em>.<em class="replaceable"><code>column_name</code></em><br /></span><span class="term"><em class="replaceable"><code>aggregate_name</code></em><br /></span><span class="term"><em class="replaceable"><code>constraint_name</code></em><br /></span><span class="term"><em class="replaceable"><code>function_name</code></em><br /></span><span class="term"><em class="replaceable"><code>operator_name</code></em><br /></span><span class="term"><em class="replaceable"><code>policy_name</code></em><br /></span><span class="term"><em class="replaceable"><code>procedure_name</code></em><br /></span><span class="term"><em class="replaceable"><code>routine_name</code></em><br /></span><span class="term"><em class="replaceable"><code>rule_name</code></em><br /></span><span class="term"><em class="replaceable"><code>trigger_name</code></em></span></dt><dd><p>
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,
<em class="replaceable"><code>relation_name</code></em> must refer
to a table, view, composite type, or foreign table.
</p></dd><dt><span class="term"><em class="replaceable"><code>table_name</code></em><br /></span><span class="term"><em class="replaceable"><code>domain_name</code></em></span></dt><dd><p>
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.
</p></dd><dt><span class="term"><em class="replaceable"><code>source_type</code></em></span></dt><dd><p>
The name of the source data type of the cast.
</p></dd><dt><span class="term"><em class="replaceable"><code>target_type</code></em></span></dt><dd><p>
The name of the target data type of the cast.
</p></dd><dt><span class="term"><em class="replaceable"><code>argmode</code></em></span></dt><dd><p>
The mode of a function, procedure, or aggregate
argument: <code class="literal">IN</code>, <code class="literal">OUT</code>,
<code class="literal">INOUT</code>, or <code class="literal">VARIADIC</code>.
If omitted, the default is <code class="literal">IN</code>.
Note that <code class="command">COMMENT</code> does not actually pay
any attention to <code class="literal">OUT</code> arguments, since only the input
arguments are needed to determine the function's identity.
So it is sufficient to list the <code class="literal">IN</code>, <code class="literal">INOUT</code>,
and <code class="literal">VARIADIC</code> arguments.
</p></dd><dt><span class="term"><em class="replaceable"><code>argname</code></em></span></dt><dd><p>
The name of a function, procedure, or aggregate argument.
Note that <code class="command">COMMENT</code> does not actually pay
any attention to argument names, since only the argument data
types are needed to determine the function's identity.
</p></dd><dt><span class="term"><em class="replaceable"><code>argtype</code></em></span></dt><dd><p>
The data type of a function, procedure, or aggregate argument.
</p></dd><dt><span class="term"><em class="replaceable"><code>large_object_oid</code></em></span></dt><dd><p>
The OID of the large object.
</p></dd><dt><span class="term"><em class="replaceable"><code>left_type</code></em><br /></span><span class="term"><em class="replaceable"><code>right_type</code></em></span></dt><dd><p>
The data type(s) of the operator's arguments (optionally
schema-qualified). Write <code class="literal">NONE</code> for the missing argument
of a prefix or postfix operator.
</p></dd><dt><span class="term"><code class="literal">PROCEDURAL</code></span></dt><dd><p>
This is a noise word.
</p></dd><dt><span class="term"><em class="replaceable"><code>type_name</code></em></span></dt><dd><p>
The name of the data type of the transform.
</p></dd><dt><span class="term"><em class="replaceable"><code>lang_name</code></em></span></dt><dd><p>
The name of the language of the transform.
</p></dd><dt><span class="term"><em class="replaceable"><code>text</code></em></span></dt><dd><p>
The new comment, written as a string literal; or <code class="literal">NULL</code>
to drop the comment.
</p></dd></dl></div></div><div class="refsect1" id="id-1.9.3.52.7"><h2>Notes</h2><p>
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.
</p></div><div class="refsect1" id="id-1.9.3.52.8"><h2>Examples</h2><p>
Attach a comment to the table <code class="literal">mytable</code>:
</p><pre class="programlisting">
COMMENT ON TABLE mytable IS 'This is my table.';
</pre><p>
Remove it again:
</p><pre class="programlisting">
COMMENT ON TABLE mytable IS NULL;
</pre><p>
</p><p>
Some more examples:
</p><pre class="programlisting">
COMMENT ON ACCESS METHOD rtree IS 'R-Tree 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 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 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 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';
</pre></div><div class="refsect1" id="id-1.9.3.52.9"><h2>Compatibility</h2><p>
There is no <code class="command">COMMENT</code> command in the SQL standard.
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