CREATE POLICY CREATE POLICY 7 SQL - Language Statements CREATE POLICY define a new policy for a table CREATE POLICY name ON table_name [ FOR { ALL | SELECT | INSERT | UPDATE | DELETE } ] [ TO { role_name | PUBLIC } [, ...] ] [ USING ( using_expression ) ] [ WITH CHECK ( check_expression ) ] The CREATE POLICY command defines a new policy for a table. Note that row level security must also be enabled on the table using ALTER TABLE in order for created policies to be applied. A policy grants the ability to SELECT, INSERT, UPDATE, or DELETE rows which match the relevant policy expression. Existing table rows are checked against the expression specified via USING, while new rows that would be created via INSERT or UPDATE are checked against the expression specified via WITH CHECK. When a USING expression returns true for a given row then that row is visible to the user, while if a 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 added, while if a false or null is returned then an error occurs. Generally, the system will enforce filter conditions imposed using security policies prior to qualifications that appear in the query itself, in order to the prevent the 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. For INSERT and UPDATE queries, WITH CHECK expressions are enforced after BEFORE triggers are fired, and before any 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. 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. 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. If multiple policies apply to a given query, they will be combined using OR. Further, for commands which can have both USING and WITH CHECK policies (ALL and UPDATE), if no WITH CHECK policy is defined then the USING policy will be used for both what rows are visible (normal USING case) and which rows will be allowed to be added (WITH CHECK case). Note that while policies will be applied for explicit queries against tables in the system, 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 which is the 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 which 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. Regarding how policy expressions interact with the user: as the expressions are added to the user's 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 RLS-enabled table. 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's rights and any policies which apply to the view owner. name The name of the policy to be created. This must be distinct from the name of any other policy for the table. table_name The name (optionally schema-qualified) of the table the policy applies to. command The command to which the policy applies. Valid options are ALL, SELECT, INSERT, UPDATE, and DELETE. ALL is the default. See below for specifics regarding how these are applied. role_name The roles to which the policy is to be applied. The default is PUBLIC, which will apply the policy to all roles. using_expression 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 and 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. check_expression Any SQL conditional expression (returning boolean). The conditional expression cannot contain any aggregate or window functions. This expression will be used with INSERT and UPDATE queries against the table if row level security is enabled and only rows where 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 which result from the update. ALL 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 combined using OR, as usual for overlapping policies. Additionally, ALL policies will be applied to both the selection side of a query and the modification side, using the USING policy for both if only a USING policy has been defined. As an example, if an UPDATE is issued, then the ALL policy will be applicable to both what the UPDATE will be able to select out as rows to be updated (with the USING expression being applied), and it will be applied to rows which result from the UPDATE statement, to check if they are permitted to be added to the table (using the WITH CHECK expression, if defined, and the USING expression otherwise). If an INSERT or UPDATE command attempts to add rows to the table which do not pass the ALL WITH CHECK expression, the entire command will be aborted. Note that if only a USING clause is specified then that clause will be used for both USING and WITH CHECK cases. SELECT Using SELECT for a policy means that it will apply to SELECT commands. The result is that only those records from the relation which pass the SELECT policy will be returned, even if other records exist in the relation. The SELECT policy only accepts the USING expression as it only ever applies in cases where records are being retrieved from the relation. INSERT Using INSERT for a policy means that it will apply to INSERT commands. Rows being inserted which do not pass this policy will result in a policy violation ERROR and the entire INSERT command will be aborted. The INSERT policy only accepts the WITH CHECK expression as it only ever applies in cases where records are being added to the relation. UPDATE Using UPDATE for a policy means that it will apply to UPDATE commands. As UPDATE involves pulling an existing record and then making changes to some portion (but possibly not all) of the record, the UPDATE policy accepts both a USING expression and a WITH CHECK expression. The USING expression will be used to determine which records the UPDATE command will see to operate against, while the WITH CHECK expression defines what rows are allowed to be added back into the relation (similar to the INSERT policy). Any rows whose resulting values do not pass the WITH CHECK expression will cause an ERROR and the entire command will be aborted. Note that if only a USING clause is specified then that clause will be used for both USING and WITH CHECK cases. DELETE Using DELETE for a policy means that it will apply to DELETE commands. Only rows which pass this policy will be seen by a DELETE command. Rows may be visible through a SELECT which are not seen by a DELETE, as they do not pass the USING expression for the DELETE, and rows which are not visible through the SELECT policy may be deleted if they pass the DELETE USING policy. The DELETE policy only accepts the USING expression as it only ever applies in cases where records are being extracted from the relation for deletion. You must be the owner of a table to create or change policies for it. In order to maintain referential integrity between two related tables, policies are not applied when the system performs checks on foreign key constraints. CREATE POLICY is a PostgreSQL extension.