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>Chapter 20. Database Roles</TD
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><H1
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><A
NAME="ROLE-ATTRIBUTES"
>20.2. Role Attributes</A
></H1
><P
> A database role can have a number of attributes that define its
privileges and interact with the client authentication system.
<P
></P
></P><DIV
CLASS="VARIABLELIST"
><DL
><DT
>login privilege</DT
><DD
><P
> Only roles that have the <TT
CLASS="LITERAL"
>LOGIN</TT
> attribute can be used
as the initial role name for a database connection. A role with
the <TT
CLASS="LITERAL"
>LOGIN</TT
> attribute can be considered the same
as a <SPAN
CLASS="QUOTE"
>"database user"</SPAN
>. To create a role with login privilege,
use either:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE ROLE <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> LOGIN;
CREATE USER <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
>;</PRE
><P>
(<TT
CLASS="COMMAND"
>CREATE USER</TT
> is equivalent to <TT
CLASS="COMMAND"
>CREATE ROLE</TT
>
except that <TT
CLASS="COMMAND"
>CREATE USER</TT
> assumes <TT
CLASS="LITERAL"
>LOGIN</TT
> by
default, while <TT
CLASS="COMMAND"
>CREATE ROLE</TT
> does not.)
</P
></DD
><DT
>superuser status</DT
><DD
><P
> A database superuser bypasses all permission checks, except the right
to log in. This is a dangerous privilege and should not be used
carelessly; it is best to do most of your work as a role that is not a
superuser. To create a new database superuser, use <TT
CLASS="LITERAL"
>CREATE
ROLE <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> SUPERUSER</TT
>. You must do
this as a role that is already a superuser.
</P
></DD
><DT
>database creation</DT
><DD
><P
> A role must be explicitly given permission to create databases
(except for superusers, since those bypass all permission
checks). To create such a role, use <TT
CLASS="LITERAL"
>CREATE ROLE
<TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> CREATEDB</TT
>.
</P
></DD
><DT
>role creation</DT
><DD
><P
> A role must be explicitly given permission to create more roles
(except for superusers, since those bypass all permission
checks). To create such a role, use <TT
CLASS="LITERAL"
>CREATE ROLE
<TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> CREATEROLE</TT
>.
A role with <TT
CLASS="LITERAL"
>CREATEROLE</TT
> privilege can alter and drop
other roles, too, as well as grant or revoke membership in them.
However, to create, alter, drop, or change membership of a
superuser role, superuser status is required;
<TT
CLASS="LITERAL"
>CREATEROLE</TT
> is insufficient for that.
</P
></DD
><DT
>initiating replication</DT
><DD
><P
> A role must explicitly be given permission to initiate streaming
replication (except for superusers, since those bypass all permission
checks). A role used for streaming replication must
have <TT
CLASS="LITERAL"
>LOGIN</TT
> permission as well. To create such a role, use
<TT
CLASS="LITERAL"
>CREATE ROLE <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> REPLICATION
LOGIN</TT
>.
</P
></DD
><DT
>password</DT
><DD
><P
> A password is only significant if the client authentication
method requires the user to supply a password when connecting
to the database. The <TT
CLASS="OPTION"
>password</TT
> and
<TT
CLASS="OPTION"
>md5</TT
> authentication methods
make use of passwords. Database passwords are separate from
operating system passwords. Specify a password upon role
creation with <TT
CLASS="LITERAL"
>CREATE ROLE
<TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> PASSWORD '<TT
CLASS="REPLACEABLE"
><I
>string</I
></TT
>'</TT
>.
</P
></DD
></DL
></DIV
><P>
A role's attributes can be modified after creation with
<TT
CLASS="COMMAND"
>ALTER ROLE</TT
>.
See the reference pages for the <A
HREF="sql-createrole.html"
>CREATE ROLE</A
>
and <A
HREF="sql-alterrole.html"
>ALTER ROLE</A
> commands for details.
</P
><DIV
CLASS="TIP"
><BLOCKQUOTE
CLASS="TIP"
><P
><B
>Tip: </B
> It is good practice to create a role that has the <TT
CLASS="LITERAL"
>CREATEDB</TT
>
and <TT
CLASS="LITERAL"
>CREATEROLE</TT
> privileges, but is not a superuser, and then
use this role for all routine management of databases and roles. This
approach avoids the dangers of operating as a superuser for tasks that
do not really require it.
</P
></BLOCKQUOTE
></DIV
><P
> A role can also have role-specific defaults for many of the run-time
configuration settings described in <A
HREF="runtime-config.html"
>Chapter 18</A
>. For example, if for some reason you
want to disable index scans (hint: not a good idea) anytime you
connect, you can use:
</P><PRE
CLASS="PROGRAMLISTING"
>ALTER ROLE myname SET enable_indexscan TO off;</PRE
><P>
This will save the setting (but not set it immediately). In
subsequent connections by this role it will appear as though
<TT
CLASS="LITERAL"
>SET enable_indexscan TO off</TT
> had been executed
just before the session started.
You can still alter this setting during the session; it will only
be the default. To remove a role-specific default setting, use
<TT
CLASS="LITERAL"
>ALTER ROLE <TT
CLASS="REPLACEABLE"
><I
>rolename</I
></TT
> RESET <TT
CLASS="REPLACEABLE"
><I
>varname</I
></TT
></TT
>.
Note that role-specific defaults attached to roles without
<TT
CLASS="LITERAL"
>LOGIN</TT
> privilege are fairly useless, since they will never
be invoked.
</P
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