COMMENT

COMMENT —定义或更改对象的 Comments

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'

where aggregate_signature is:

* |
[ argmode ] [ argname ] argtype [ , ... ] |
[ [ argmode ] [ argname ] argtype [ , ... ] ] ORDER BY [ argmode ] [ argname ] argtype [ , ... ]

Description

COMMENT存储有关数据库对象的 Comments。

每个对象仅存储一个 Comments 字符串，因此要修改 Comments，对同一对象发出新的COMMENT命令。要删除 Comment，请写NULL代替文本字符串。删除对象时，Comments 会自动删除。

对于大多数对象，只有对象的所有者才能设置 Comments。角色没有所有者，因此COMMENT ON ROLE的规则是您必须是超级用户才能对超级用户角色进行 Comment，或者具有CREATEROLE特权才能对非超级用户角色进行 Comment。同样，访问方法也没有所有者。您必须是超级用户才能 Comment 访问方法。当然，超级用户可以对任何内容发表 Comment。

可以使用 psql 的\d系列命令查看 Comments。可以在 psql 使用的相同内置函数(即obj_description，col_description和shobj_description(请参见Table 9.68))上构建其他用于检索 Comments 的用户界面。

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

  • 要 Comments 的对象的名称。表，集合，排序规则，转换，域，外部表，函数，索引，运算符，运算符类，运算符族，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通过模式限定。在对列进行 Comments 时，* relation_name *必须引用表，视图，组合类型或外部表。

• table_name
domain_name

  • 在约束，触发器，规则或策略上创建 Comments 时，这些参数指定在其上定义该对象的表或域的名称。

• source_type

  • 强制转换的源数据类型的名称。

• target_type

  • 强制转换的目标数据类型的名称。

• argmode

  • 函数，过程或聚合参数的模式：IN，OUT，INOUT或VARIADIC。如果省略，则默认值为IN。注意COMMENT实际上并没有注意OUT参数，因为只需要 Importing 参数即可确定函数的身份。因此，列出IN，INOUT和VARIADIC参数就足够了。

• argname

  • 函数，过程或聚合参数的名称。注意COMMENT实际上并没有注意参数名称，因为只需要参数数据类型即可确定函数的身份。

• argtype

  • 函数，过程或聚合参数的数据类型。

• large_object_oid

  • 大对象的 OID。

• left_type
right_type

  • 运算符参数的数据类型(可选，模式限定)。ImportingNONE作为前缀或后缀运算符的缺少参数。

• PROCEDURAL

  • 这是一个干扰词。

• type_name

  • 转换的数据类型的名称。

• lang_name

  • 转换语言的名称。

• text

  • 新 Comments，以字符串 Literals 形式表示；或NULL删除 Comment。

Notes

当前没有用于查看 Comments 的安全机制：连接到数据库的任何用户都可以查看该数据库中对象的所有 Comments。对于共享对象，例如数据库，角色和表空间，Comments 是全局存储的，因此连接到集群中任何数据库的任何用户都可以查看共享对象的所有 Comments。因此，请勿在 Comment 中添加对安全性至关重要的信息。

Examples

在表格mytable上添加 Comment：

COMMENT ON TABLE mytable IS 'This is my table.';

再次删除：

COMMENT ON TABLE mytable IS NULL;

其他示例：

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';

Compatibility

SQL 标准中没有COMMENT命令。