======= COMMENT ======= .. container:: refentry :name: SQL-COMMENT .. container:: titlepage .. container:: refnamediv .. rubric:: COMMENT :name: comment COMMENT — 定义或者更改一个对象的注释 .. container:: refsynopsisdiv .. rubric:: 大纲 :name: 大纲 .. code:: 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 'text' 其中 aggregate_signature 是： * | [ argmode ] [ argname ] argtype [ , ... ] | [ [ argmode ] [ argname ] argtype [ , ... ] ] ORDER BY [ argmode ] [ argname ] argtype [ , ... ] .. container:: refsect1 :name: id-1.9.3.52.5 .. rubric:: 描述 :name: 描述 ``COMMENT``\ 存储关于一个数据库对象的注释。 对每一个对象只保存一个注释字符串，因此为了修改一段注释，对同一个对象 发出一个新的\ ``COMMENT``\ 命令。要移除一段注释，可在文 本字符串的位置上写上\ ``NULL``\ 。当对象被删除时，其注释 也会被自动删除。 对大部分类型的对象，只有对象的拥有者可以设置注释。角色没有拥有者，因此 ``COMMENT ON ROLE``\ 的规则是你必须作为一个超级用户来对一个 超级用户角色设置注释，或者具有\ ``CREATEROLE``\ 特权来对非超级用 户角色设置注释。同样的，访问方法也没有拥有者，你必须作为一个超级用户来 对一个访问方法设置注释。当然，一个超级用户可以对任何东西设置注释。 使用psql的\ ``\d`` 命令家族可以查看注释。其他检索注释的用户接口可以构建在 psql使用的内建函数之上，即 ``obj_description``\ 、\ ``col_description`` 以及\ ``shobj_description`` （见\ `表 `__\ ）。 .. container:: refsect1 :name: id-1.9.3.52.6 .. rubric:: 参数 :name: 参数 .. container:: variablelist ``object_name`` \ ``relation_name``.\ ``column_name`` \ ``aggregate_name`` \ ``constraint_name`` \ ``function_name`` \ ``operator_name`` \ ``policy_name`` \ ``procedure_name`` \ ``routine_name`` \ ``rule_name`` \ ``trigger_name`` 要被注释的对象的名称。表、聚集、排序方式、转换、域、外部表、函数、 索引、操作符、操作符类、操作符族、存储过程、例程、序列、统计信息、文本搜索对象、类型和视图 的名称可以被模式限定。在注释一列时， ``relation_name``\ 必须 引用一个表、视图、组合类型或者外部表。 ``table_name`` ``domain_name`` 当在一个约束、触发器、规则或者策略上创建一段注释时，这些参数指定在其上定义 该对象的表或域的名称。 ``source_type`` 造型的源数据类型的名称。 ``target_type`` 造型的目标数据类型的名称。 ``argmode`` 一个函数，存储过程或者聚集函数的参数的模式：\ ``IN``\ 、 ``OUT``\ 、\ ``INOUT``\ 或者\ ``VARIADIC``\ 。 如果被省略，默认值是\ ``IN``\ 。注意 ``COMMENT``\ 并不真正关心 ``OUT``\ 参数，因为决定函数的身份只需要输入参数。因此 列出\ ``IN``\ 、\ ``INOUT``\ 和\ ``VARIADIC`` 参数就足够了。 ``argname`` 一个函数，存储过程或者聚集函数参数的名称。注意 ``COMMENT``\ 并不真正关心参数名称， 因为决定函数的身份只需要参数数据类型。 ``argtype`` 一个函数，存储过程或者聚集函数参数的数据类型。 ``large_object_oid`` 大对象的 OID。 ``left_type`` \ ``right_type`` 操作符的参数的数据类型（可以是模式限定的）。对一个前缀后后缀操作符 的缺失参数可以写\ ``NONE``\ 。 ``PROCEDURAL`` 这是一个噪声词。 ``type_name`` 该转换的数据类型的名称。 ``lang_name`` 该转换的语言的名称。 ``text`` 写成一个字符串的新注释。如果要删除注释，写成\ ``NULL``\ 。 .. container:: refsect1 :name: id-1.9.3.52.7 .. rubric:: 注解 :name: 注解 当前对查看注释没有安全机制：任何连接到一个数据库的用户能够看到 该数据库中所有对象的注释。对于数据库、角色、表空间这类共享对象， 注释被全局存储，因此连接到集簇中任何数据库的任何用户可以看到共 享对象的所有注释。因此，不要在注释中放置有安全性风险的信息。 .. container:: refsect1 :name: id-1.9.3.52.8 .. rubric:: 示例 :name: 示例 为表\ ``mytable``\ 附加一段注释： .. code:: programlisting COMMENT ON TABLE mytable IS 'This is my table.'; 移除它： .. code:: programlisting COMMENT ON TABLE mytable IS NULL; 更多的一些例子： .. code:: 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'; .. container:: refsect1 :name: id-1.9.3.52.9 .. rubric:: 兼容性 :name: 兼容性 SQL 标准中没有\ ``COMMENT``\ 命令。