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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 } [, ...]

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

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

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

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

Description

The GRANT command gives specific permissions on an object (table, view, sequence, database, function, procedural language, or schema) to one or more users or groups of users. These permissions 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. Note that 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.

There is no need to grant privileges to the creator of an object, as the creator has all privileges by default. (The creator could, however, choose to revoke some of his own privileges for safety.) Note that the ability to grant and revoke privileges is inherent in the creator and cannot be lost. The right to drop an object, or to alter it in any way not described by a grantable right, is likewise inherent in the creator, and cannot be granted or revoked.

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 creator 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. 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. SELECT ... FOR UPDATE also requires this privilege (besides 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.

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 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.

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 \dp command to obtain information about existing privileges, for example:

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

The entries shown by \dp 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)

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 field 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

SQL92

The PRIVILEGES key word in ALL PRIVILEGES is required. SQL does not support setting the privileges on more than one table per command.

The SQL92 syntax for GRANT allows setting privileges for individual columns within a table, and allows setting a privilege to grant the same privileges to others:

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

SQL allows to grant the USAGE privilege on other kinds of objects: CHARACTER SET, COLLATION, TRANSLATION, DOMAIN.

The TRIGGER privilege was introduced in SQL99. The RULE privilege is a PostgreSQL extension.

See Also

REVOKE

Comments


Feb. 10, 2005, 3:28 p.m.

This is a response to Wagner Correa Ramos' point about functions and tables. Yes, PostgreSQL and Standard SQL routines (functions) can access a table without the executor having direct priviliges on it.

The CREATE FUNCTION clause SECURITY DEFINER (see that command) makes the function run with the priviliges of the user who created it. Otherwise, the INVOKER's priviliges are used.

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