path: root/doc/src/sgml/man7/CREATE_POLICY.7

'\" t
.\"     Title: CREATE POLICY
.\"    Author: The PostgreSQL Global Development Group
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 2024
.\"    Manual: PostgreSQL 16.2 Documentation
.\"    Source: PostgreSQL 16.2
.\"  Language: English
.\"
.TH "CREATE POLICY" "7" "2024" "PostgreSQL 16.2" "PostgreSQL 16.2 Documentation"
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.SH "NAME"
CREATE_POLICY \- define a new row\-level security policy for a table
.SH "SYNOPSIS"
.sp
.nf
CREATE POLICY \fIname\fR ON \fItable_name\fR
    [ AS { PERMISSIVE | RESTRICTIVE } ]
    [ FOR { ALL | SELECT | INSERT | UPDATE | DELETE } ]
    [ TO { \fIrole_name\fR | PUBLIC | CURRENT_ROLE | CURRENT_USER | SESSION_USER } [, \&.\&.\&.] ]
    [ USING ( \fIusing_expression\fR ) ]
    [ WITH CHECK ( \fIcheck_expression\fR ) ]
.fi
.SH "DESCRIPTION"
.PP
The
\fBCREATE POLICY\fR
command defines a new row\-level security policy for a table\&. Note that row\-level security must be enabled on the table (using
\fBALTER TABLE \&.\&.\&. ENABLE ROW LEVEL SECURITY\fR) in order for created policies to be applied\&.
.PP
A policy grants the permission to select, insert, update, or delete rows that match the relevant policy expression\&. Existing table rows are checked against the expression specified in
USING, while new rows that would be created via
INSERT
or
UPDATE
are checked against the expression specified in
WITH CHECK\&. When a
USING
expression returns true for a given row then that row is visible to the user, while if false or null is returned then the row is not visible\&. When a
WITH CHECK
expression returns true for a row then that row is inserted or updated, while if false or null is returned then an error occurs\&.
.PP
For
\fBINSERT\fR,
\fBUPDATE\fR, and
\fBMERGE\fR
statements,
WITH CHECK
expressions are enforced after
BEFORE
triggers are fired, and before any actual data modifications are made\&. Thus a
BEFORE ROW
trigger may modify the data to be inserted, affecting the result of the security policy check\&.
WITH CHECK
expressions are enforced before any other constraints\&.
.PP
Policy names are per\-table\&. Therefore, one policy name can be used for many different tables and have a definition for each table which is appropriate to that table\&.
.PP
Policies can be applied for specific commands or for specific roles\&. The default for newly created policies is that they apply for all commands and roles, unless otherwise specified\&. Multiple policies may apply to a single command; see below for more details\&.
Table\ \&292
summarizes how the different types of policy apply to specific commands\&.
.PP
For policies that can have both
USING
and
WITH CHECK
expressions (ALL
and
UPDATE), if no
WITH CHECK
expression is defined, then the
USING
expression will be used both to determine which rows are visible (normal
USING
case) and which new rows will be allowed to be added (WITH CHECK
case)\&.
.PP
If row\-level security is enabled for a table, but no applicable policies exist, a
\(lqdefault deny\(rq
policy is assumed, so that no rows will be visible or updatable\&.
.SH "PARAMETERS"
.PP
\fIname\fR
.RS 4
The name of the policy to be created\&. This must be distinct from the name of any other policy for the table\&.
.RE
.PP
\fItable_name\fR
.RS 4
The name (optionally schema\-qualified) of the table the policy applies to\&.
.RE
.PP
PERMISSIVE
.RS 4
Specify that the policy is to be created as a permissive policy\&. All permissive policies which are applicable to a given query will be combined together using the Boolean
\(lqOR\(rq
operator\&. By creating permissive policies, administrators can add to the set of records which can be accessed\&. Policies are permissive by default\&.
.RE
.PP
RESTRICTIVE
.RS 4
Specify that the policy is to be created as a restrictive policy\&. All restrictive policies which are applicable to a given query will be combined together using the Boolean
\(lqAND\(rq
operator\&. By creating restrictive policies, administrators can reduce the set of records which can be accessed as all restrictive policies must be passed for each record\&.
.sp
Note that there needs to be at least one permissive policy to grant access to records before restrictive policies can be usefully used to reduce that access\&. If only restrictive policies exist, then no records will be accessible\&. When a mix of permissive and restrictive policies are present, a record is only accessible if at least one of the permissive policies passes, in addition to all the restrictive policies\&.
.RE
.PP
\fIcommand\fR
.RS 4
The command to which the policy applies\&. Valid options are
\fBALL\fR,
\fBSELECT\fR,
\fBINSERT\fR,
\fBUPDATE\fR, and
\fBDELETE\fR\&.
\fBALL\fR
is the default\&. See below for specifics regarding how these are applied\&.
.RE
.PP
\fIrole_name\fR
.RS 4
The role(s) to which the policy is to be applied\&. The default is
PUBLIC, which will apply the policy to all roles\&.
.RE
.PP
\fIusing_expression\fR
.RS 4
Any
SQL
conditional expression (returning
boolean)\&. The conditional expression cannot contain any aggregate or window functions\&. This expression will be added to queries that refer to the table if row\-level security is enabled\&. Rows for which the expression returns true will be visible\&. Any rows for which the expression returns false or null will not be visible to the user (in a
\fBSELECT\fR), and will not be available for modification (in an
\fBUPDATE\fR
or
\fBDELETE\fR)\&. Such rows are silently suppressed; no error is reported\&.
.RE
.PP
\fIcheck_expression\fR
.RS 4
Any
SQL
conditional expression (returning
boolean)\&. The conditional expression cannot contain any aggregate or window functions\&. This expression will be used in
\fBINSERT\fR
and
\fBUPDATE\fR
queries against the table if row\-level security is enabled\&. Only rows for which the expression evaluates to true will be allowed\&. An error will be thrown if the expression evaluates to false or null for any of the records inserted or any of the records that result from the update\&. Note that the
\fIcheck_expression\fR
is evaluated against the proposed new contents of the row, not the original contents\&.
.RE
.SS "Per\-Command Policies"
.PP
ALL
.RS 4
Using
ALL
for a policy means that it will apply to all commands, regardless of the type of command\&. If an
ALL
policy exists and more specific policies exist, then both the
ALL
policy and the more specific policy (or policies) will be applied\&. Additionally,
ALL
policies will be applied to both the selection side of a query and the modification side, using the
USING
expression for both cases if only a
USING
expression has been defined\&.
.sp
As an example, if an
UPDATE
is issued, then the
ALL
policy will be applicable both to what the
UPDATE
will be able to select as rows to be updated (applying the
USING
expression), and to the resulting updated rows, to check if they are permitted to be added to the table (applying the
WITH CHECK
expression, if defined, and the
USING
expression otherwise)\&. If an
\fBINSERT\fR
or
\fBUPDATE\fR
command attempts to add rows to the table that do not pass the
ALL
policy\*(Aqs
WITH CHECK
expression, the entire command will be aborted\&.
.RE
.PP
SELECT
.RS 4
Using
SELECT
for a policy means that it will apply to
SELECT
queries and whenever
SELECT
permissions are required on the relation the policy is defined for\&. The result is that only those records from the relation that pass the
SELECT
policy will be returned during a
SELECT
query, and that queries that require
SELECT
permissions, such as
UPDATE, will also only see those records that are allowed by the
SELECT
policy\&. A
SELECT
policy cannot have a
WITH CHECK
expression, as it only applies in cases where records are being retrieved from the relation\&.
.RE
.PP
INSERT
.RS 4
Using
INSERT
for a policy means that it will apply to
INSERT
commands and
MERGE
commands that contain
INSERT
actions\&. Rows being inserted that do not pass this policy will result in a policy violation error, and the entire
INSERT
command will be aborted\&. An
INSERT
policy cannot have a
USING
expression, as it only applies in cases where records are being added to the relation\&.
.sp
Note that
INSERT
with
ON CONFLICT DO UPDATE
checks
INSERT
policies\*(Aq
WITH CHECK
expressions only for rows appended to the relation by the
INSERT
path\&.
.RE
.PP
UPDATE
.RS 4
Using
UPDATE
for a policy means that it will apply to
UPDATE,
SELECT FOR UPDATE
and
SELECT FOR SHARE
commands, as well as auxiliary
ON CONFLICT DO UPDATE
clauses of
INSERT
commands\&.
MERGE
commands containing
UPDATE
actions are affected as well\&. Since
UPDATE
involves pulling an existing record and replacing it with a new modified record,
UPDATE
policies accept both a
USING
expression and a
WITH CHECK
expression\&. The
USING
expression determines which records the
UPDATE
command will see to operate against, while the
WITH CHECK
expression defines which modified rows are allowed to be stored back into the relation\&.
.sp
Any rows whose updated values do not pass the
WITH CHECK
expression will cause an error, and the entire command will be aborted\&. If only a
USING
clause is specified, then that clause will be used for both
USING
and
WITH CHECK
cases\&.
.sp
Typically an
UPDATE
command also needs to read data from columns in the relation being updated (e\&.g\&., in a
WHERE
clause or a
RETURNING
clause, or in an expression on the right hand side of the
SET
clause)\&. In this case,
SELECT
rights are also required on the relation being updated, and the appropriate
SELECT
or
ALL
policies will be applied in addition to the
UPDATE
policies\&. Thus the user must have access to the row(s) being updated through a
SELECT
or
ALL
policy in addition to being granted permission to update the row(s) via an
UPDATE
or
ALL
policy\&.
.sp
When an
INSERT
command has an auxiliary
ON CONFLICT DO UPDATE
clause, if the
UPDATE
path is taken, the row to be updated is first checked against the
USING
expressions of any
UPDATE
policies, and then the new updated row is checked against the
WITH CHECK
expressions\&. Note, however, that unlike a standalone
UPDATE
command, if the existing row does not pass the
USING
expressions, an error will be thrown (the
UPDATE
path will
\fInever\fR
be silently avoided)\&.
.RE
.PP
DELETE
.RS 4
Using
DELETE
for a policy means that it will apply to
DELETE
commands\&. Only rows that pass this policy will be seen by a
DELETE
command\&. There can be rows that are visible through a
SELECT
that are not available for deletion, if they do not pass the
USING
expression for the
DELETE
policy\&.
.sp
In most cases a
DELETE
command also needs to read data from columns in the relation that it is deleting from (e\&.g\&., in a
WHERE
clause or a
RETURNING
clause)\&. In this case,
SELECT
rights are also required on the relation, and the appropriate
SELECT
or
ALL
policies will be applied in addition to the
DELETE
policies\&. Thus the user must have access to the row(s) being deleted through a
SELECT
or
ALL
policy in addition to being granted permission to delete the row(s) via a
DELETE
or
ALL
policy\&.
.sp
A
DELETE
policy cannot have a
WITH CHECK
expression, as it only applies in cases where records are being deleted from the relation, so that there is no new row to check\&.
.RE
.sp
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.B Table\ \&292.\ \&Policies Applied by Command Type
.TS
allbox tab(:);
lB lB lB lB s lB
^ lB lB lB lB lB.
T{
Command
T}:T{
SELECT/ALL policy
T}:T{
INSERT/ALL policy
T}:T{
UPDATE/ALL policy
T}:T{
DELETE/ALL policy
T}
:T{
USING expression
T}:T{
WITH CHECK expression
T}:T{
USING expression
T}:T{
WITH CHECK expression
T}:T{
USING expression
T}
.T&
l l l l l l
l l l l l l
l l l l l l
l l l l l l
l l l l l l
l l l l l l
l l l l l l
l s s s s s.
T{
\fBSELECT\fR
T}:T{
Existing row
T}:T{
\(em
T}:T{
\(em
T}:T{
\(em
T}:T{
\(em
T}
T{
\fBSELECT FOR UPDATE/SHARE\fR
T}:T{
Existing row
T}:T{
\(em
T}:T{
Existing row
T}:T{
\(em
T}:T{
\(em
T}
T{
\fBINSERT\fR / \fBMERGE \&.\&.\&. THEN INSERT\fR
T}:T{
\(em
T}:T{
New row
T}:T{
\(em
T}:T{
\(em
T}:T{
\(em
T}
T{
\fBINSERT \&.\&.\&. RETURNING\fR
T}:T{
New row [a]
T}:T{
New row
T}:T{
\(em
T}:T{
\(em
T}:T{
\(em
T}
T{
\fBUPDATE\fR / \fBMERGE \&.\&.\&. THEN UPDATE\fR
T}:T{
Existing & new rows [a]
T}:T{
\(em
T}:T{
Existing row
T}:T{
New row
T}:T{
\(em
T}
T{
\fBDELETE\fR
T}:T{
Existing row [a]
T}:T{
\(em
T}:T{
\(em
T}:T{
\(em
T}:T{
Existing row
T}
T{
\fBON CONFLICT DO UPDATE\fR
T}:T{
Existing & new rows
T}:T{
\(em
T}:T{
Existing row
T}:T{
New row
T}:T{
\(em
T}
T{
----
.br
[a]
If read access is required to the existing or new row (for example, a
WHERE
or
RETURNING
clause that refers to columns from the relation)\&.
T}
.TE
.sp 1
.SS "Application of Multiple Policies"
.PP
When multiple policies of different command types apply to the same command (for example,
SELECT
and
UPDATE
policies applied to an
UPDATE
command), then the user must have both types of permissions (for example, permission to select rows from the relation as well as permission to update them)\&. Thus the expressions for one type of policy are combined with the expressions for the other type of policy using the
AND
operator\&.
.PP
When multiple policies of the same command type apply to the same command, then there must be at least one
PERMISSIVE
policy granting access to the relation, and all of the
RESTRICTIVE
policies must pass\&. Thus all the
PERMISSIVE
policy expressions are combined using
OR, all the
RESTRICTIVE
policy expressions are combined using
AND, and the results are combined using
AND\&. If there are no
PERMISSIVE
policies, then access is denied\&.
.PP
Note that, for the purposes of combining multiple policies,
ALL
policies are treated as having the same type as whichever other type of policy is being applied\&.
.PP
For example, in an
UPDATE
command requiring both
SELECT
and
UPDATE
permissions, if there are multiple applicable policies of each type, they will be combined as follows:
.sp
.if n \{\
.RS 4
.\}
.nf
\fIexpression\fR from RESTRICTIVE SELECT/ALL policy 1
AND
\fIexpression\fR from RESTRICTIVE SELECT/ALL policy 2
AND
\&.\&.\&.
AND
(
  \fIexpression\fR from PERMISSIVE SELECT/ALL policy 1
  OR
  \fIexpression\fR from PERMISSIVE SELECT/ALL policy 2
  OR
  \&.\&.\&.
)
AND
\fIexpression\fR from RESTRICTIVE UPDATE/ALL policy 1
AND
\fIexpression\fR from RESTRICTIVE UPDATE/ALL policy 2
AND
\&.\&.\&.
AND
(
  \fIexpression\fR from PERMISSIVE UPDATE/ALL policy 1
  OR
  \fIexpression\fR from PERMISSIVE UPDATE/ALL policy 2
  OR
  \&.\&.\&.
)
.fi
.if n \{\
.RE
.\}
.SH "NOTES"
.PP
You must be the owner of a table to create or change policies for it\&.
.PP
While policies will be applied for explicit queries against tables in the database, they are not applied when the system is performing internal referential integrity checks or validating constraints\&. This means there are indirect ways to determine that a given value exists\&. An example of this is attempting to insert a duplicate value into a column that is a primary key or has a unique constraint\&. If the insert fails then the user can infer that the value already exists\&. (This example assumes that the user is permitted by policy to insert records which they are not allowed to see\&.) Another example is where a user is allowed to insert into a table which references another, otherwise hidden table\&. Existence can be determined by the user inserting values into the referencing table, where success would indicate that the value exists in the referenced table\&. These issues can be addressed by carefully crafting policies to prevent users from being able to insert, delete, or update records at all which might possibly indicate a value they are not otherwise able to see, or by using generated values (e\&.g\&., surrogate keys) instead of keys with external meanings\&.
.PP
Generally, the system will enforce filter conditions imposed using security policies prior to qualifications that appear in user queries, in order to prevent inadvertent exposure of the protected data to user\-defined functions which might not be trustworthy\&. However, functions and operators marked by the system (or the system administrator) as
LEAKPROOF
may be evaluated before policy expressions, as they are assumed to be trustworthy\&.
.PP
Since policy expressions are added to the user\*(Aqs query directly, they will be run with the rights of the user running the overall query\&. Therefore, users who are using a given policy must be able to access any tables or functions referenced in the expression or they will simply receive a permission denied error when attempting to query the table that has row\-level security enabled\&. This does not change how views work, however\&. As with normal queries and views, permission checks and policies for the tables which are referenced by a view will use the view owner\*(Aqs rights and any policies which apply to the view owner, except if the view is defined using the
security_invoker
option (see
\fBCREATE VIEW\fR)\&.
.PP
No separate policy exists for
\fBMERGE\fR\&. Instead, the policies defined for
\fBSELECT\fR,
\fBINSERT\fR,
\fBUPDATE\fR, and
\fBDELETE\fR
are applied while executing
\fBMERGE\fR, depending on the actions that are performed\&.
.PP
Additional discussion and practical examples can be found in
Section\ \&5.8\&.
.SH "COMPATIBILITY"
.PP
\fBCREATE POLICY\fR
is a
PostgreSQL
extension\&.
.SH "SEE ALSO"
ALTER POLICY (\fBALTER_POLICY\fR(7)), DROP POLICY (\fBDROP_POLICY\fR(7)), ALTER TABLE (\fBALTER_TABLE\fR(7))