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GRANT

Name

GRANT -- define access privileges

Synopsis

GRANT { { SELECT | INSERT | UPDATE | DELETE | RULE | REFERENCES | TRIGGER }
    [,...] | ALL [ PRIVILEGES ] }
    ON [ TABLE ] tablename [, ...]
    TO { username | GROUP groupname | PUBLIC } [, ...] [ WITH GRANT OPTION ]

GRANT { { CREATE | TEMPORARY | TEMP } [,...] | ALL [ PRIVILEGES ] }
    ON DATABASE dbname [, ...]
    TO { username | GROUP groupname | PUBLIC } [, ...] [ WITH GRANT OPTION ]

GRANT { EXECUTE | ALL [ PRIVILEGES ] }
    ON FUNCTION funcname ([type, ...]) [, ...]
    TO { username | GROUP groupname | PUBLIC } [, ...] [ WITH GRANT OPTION ]

GRANT { USAGE | ALL [ PRIVILEGES ] }
    ON LANGUAGE langname [, ...]
    TO { username | GROUP groupname | PUBLIC } [, ...] [ WITH GRANT OPTION ]

GRANT { { CREATE | USAGE } [,...] | ALL [ PRIVILEGES ] }
    ON SCHEMA schemaname [, ...]
    TO { username | GROUP groupname | PUBLIC } [, ...] [ WITH GRANT OPTION ]

Description

The GRANT command gives specific privileges on an object (table, view, sequence, database, function, procedural language, or schema) to one or more users or groups of users. These privileges are added to those already granted, if any.

The key word PUBLIC indicates that the privileges are to be granted to all users, including those that may be created later. PUBLIC may be thought of as an implicitly defined group that always includes all users. Any particular user will have the sum of privileges granted directly to him, privileges granted to any group he is presently a member of, and privileges granted to PUBLIC.

If WITH GRANT OPTION is specified, the recipient of the privilege may in turn grant it to others. By default this is not allowed. Grant options can only be granted to individual users, not to groups or PUBLIC.

There is no need to grant privileges to the owner of an object (usually the user that created it), as the owner has all privileges by default. (The owner could, however, choose to revoke some of his own privileges for safety.) The right to drop an object, or to alter its definition in any way is not described by a grantable privilege; it is inherent in the owner, and cannot be granted or revoked. It is not possible for the owner's grant options to be revoked, either.

Depending on the type of object, the initial default privileges may include granting some privileges to PUBLIC. The default is no public access for tables and schemas; TEMP table creation privilege for databases; EXECUTE privilege for functions; and USAGE privilege for languages. The object owner may of course revoke these privileges. (For maximum security, issue the REVOKE in the same transaction that creates the object; then there is no window in which another user may use the object.)

The possible privileges are:

SELECT

Allows SELECT from any column of the specified table, view, or sequence. Also allows the use of COPY TO. This privilege is also needed to reference existing column values in UPDATE or DELETE. For sequences, this privilege also allows the use of the currval function.

INSERT

Allows INSERT of a new row into the specified table. Also allows COPY FROM.

UPDATE

Allows UPDATE of any column of the specified table. (In practice, any nontrivial UPDATE command will require SELECT privilege as well, since it must reference table columns to determine which rows to update, and/or to compute new values for columns.) SELECT ... FOR UPDATE also requires this privilege, in addition to the SELECT privilege. For sequences, this privilege allows the use of the nextval and setval functions.

DELETE

Allows DELETE of a row from the specified table. (In practice, any nontrivial DELETE command will require SELECT privilege as well, since it must reference table columns to determine which rows to delete.)

RULE

Allows the creation of a rule on the table/view. (See CREATE RULE statement.)

REFERENCES

To create a foreign key constraint, it is necessary to have this privilege on both the referencing and referenced tables.

TRIGGER

Allows the creation of a trigger on the specified table. (See CREATE TRIGGER statement.)

CREATE

For databases, allows new schemas to be created within the database.

For schemas, allows new objects to be created within the schema. To rename an existing object, you must own the object and have this privilege for the containing schema.

TEMPORARY
TEMP

Allows temporary tables to be created while using the specified database.

EXECUTE

Allows the use of the specified function and the use of any operators that are implemented on top of the function. This is the only type of privilege that is applicable to functions. (This syntax works for aggregate functions, as well.)

USAGE

For procedural languages, allows the use of the specified language for the creation of functions in that language. This is the only type of privilege that is applicable to procedural languages.

For schemas, allows access to objects contained in the specified schema (assuming that the objects' own privilege requirements are also met). Essentially this allows the grantee to "look up" objects within the schema.

ALL PRIVILEGES

Grant all of the privileges applicable to the object at once. The PRIVILEGES key word is optional in PostgreSQL, though it is required by strict SQL.

The privileges required by other commands are listed on the reference page of the respective command.

Notes

The REVOKE command is used to revoke access privileges.

It should be noted that database superusers can access all objects regardless of object privilege settings. This is comparable to the rights of root in a Unix system. As with root, it's unwise to operate as a superuser except when absolutely necessary.

If a superuser chooses to issue a GRANT or REVOKE command, the command is performed as though it were issued by the owner of the affected object. In particular, privileges granted via such a command will appear to have been granted by the object owner.

Currently, to grant privileges in PostgreSQL to only a few columns, you must create a view having the desired columns and then grant privileges to that view.

Use psql's \z command to obtain information about existing privileges, for example:

=> \z mytable

        Access privileges for database "lusitania"
 Schema |  Table  |           Access privileges
--------+---------+---------------------------------------
 public | mytable | {=r/postgres,miriam=arwdRxt/postgres,"group todos=arw/postgres"}
(1 row)

The entries shown by \z are interpreted thus:

              =xxxx -- privileges granted to PUBLIC
         uname=xxxx -- privileges granted to a user
   group gname=xxxx -- privileges granted to a group

                  r -- SELECT ("read")
                  w -- UPDATE ("write")
                  a -- INSERT ("append")
                  d -- DELETE
                  R -- RULE
                  x -- REFERENCES
                  t -- TRIGGER
                  X -- EXECUTE
                  U -- USAGE
                  C -- CREATE
                  T -- TEMPORARY
            arwdRxt -- ALL PRIVILEGES (for tables)
                  * -- grant option for preceding privilege

              /yyyy -- user who granted this privilege

The above example display would be seen by user miriam after creating table mytable and doing

GRANT SELECT ON mytable TO PUBLIC;
GRANT SELECT, UPDATE, INSERT ON mytable TO GROUP todos;

If the "Access privileges" column is empty for a given object, it means the object has default privileges (that is, its privileges column is null). Default privileges always include all privileges for the owner, and may include some privileges for PUBLIC depending on the object type, as explained above. The first GRANT or REVOKE on an object will instantiate the default privileges (producing, for example, {=,miriam=arwdRxt}) and then modify them per the specified request.

Examples

Grant insert privilege to all users on table films:

GRANT INSERT ON films TO PUBLIC;

Grant all privileges to user manuel on view kinds:

GRANT ALL PRIVILEGES ON kinds TO manuel;

Compatibility

According to the SQL standard, the PRIVILEGES key word in ALL PRIVILEGES is required. The SQL standard does not support setting the privileges on more than one object per command.

The SQL standard allows setting privileges for individual columns within a table:

GRANT privileges
    ON table [ ( column [, ...] ) ] [, ...]
    TO { PUBLIC | username [, ...] } [ WITH GRANT OPTION ]

The SQL standard provides for a USAGE privilege on other kinds of objects: character sets, collations, translations, domains.

The RULE privilege, and privileges on databases, schemas, languages, and sequences are PostgreSQL extensions.

See Also

REVOKE

Comments


Jan. 13, 2005, 8:15 a.m.

AFAICT, the UPDATE privilege is needed for LOCK TABLE.


Dec. 8, 2005, 8:08 p.m.

To "SEE" some of access privileges, look directly at system tables:

> select * from pg_user;
usename | usesysid | usecreatedb | usesuper | usecatupd | passwd | valuntil | useconfig
------------+----------+-------------+----------+-----------+----------+----------+-----------
postgres | 1 | t | t | t | ******** | |
denli | 100 | t | f | f | ******** | |


April 14, 2006, 5:19 a.m.

Note that granting 'all' to a database grants the C and T permissions. Confusingly, this does *not* grant access to the tables inside the database.

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