How to fix 0P000: invalid_role_specification in PostgreSQL

First, check if the role you're trying to use actually exists in PostgreSQL's system catalog:

SELECT rolname FROM pg_roles WHERE rolname = 'your_role_name';

Replace 'your_role_name' with the actual role name from your error. If this query returns no rows, the role doesn't exist.

To see all available roles in your database:

SELECT rolname FROM pg_roles ORDER BY rolname;

This will help you identify if there's a typo in the role name or if the role was never created.

If the role doesn't exist and you need to create it, use the CREATE ROLE command:

CREATE ROLE your_role_name;

For a role that can log in (a user), add the LOGIN attribute:

CREATE ROLE your_username WITH LOGIN PASSWORD 'secure_password';

For a role with additional privileges:

CREATE ROLE admin_role WITH
  LOGIN
  CREATEDB
  CREATEROLE
  PASSWORD 'secure_password';

You can also use the CREATE USER shorthand, which automatically includes the LOGIN privilege:

CREATE USER your_username WITH PASSWORD 'secure_password';

PostgreSQL role names must follow these rules:

- Start with a letter (a-z) or underscore (_)
- Contain only letters, digits, underscores, and dollar signs ($)
- Not exceed 63 characters in length
- Reserved keywords must be quoted with double quotes

If your role name violates these rules or uses reserved keywords, quote it properly:

-- Invalid (reserved keyword)
CREATE ROLE user;  -- ERROR

-- Valid (quoted)
CREATE ROLE "user";  -- OK

-- Also valid with double quotes for special characters
CREATE ROLE "my-role";
CREATE ROLE "Role With Spaces";

When referencing quoted role names in subsequent commands, always use the same quoting:

GRANT SELECT ON table_name TO "my-role";

If the role exists but you still get the error, check if your current user has permission to reference it:

-- Check your current role
SELECT current_user;

-- Check if you're a member of the target role
SELECT
  r.rolname AS role_name,
  m.rolname AS member_name
FROM pg_roles r
LEFT JOIN pg_auth_members am ON r.oid = am.roleid
LEFT JOIN pg_roles m ON am.member = m.oid
WHERE r.rolname = 'target_role_name';

For SET ROLE operations, you need to be a member of the role or be a superuser:

-- Grant membership to allow SET ROLE
GRANT target_role_name TO your_username;

Only superusers or roles with CREATEROLE attribute can grant role memberships.

If you recently dropped or renamed a role, update any scripts, application code, or configuration files that reference it:

-- Check for granted privileges that might reference old roles
SELECT grantee, table_name, privilege_type
FROM information_schema.table_privileges
WHERE grantee = 'old_role_name';

If you need to rename a role instead of creating a new one:

ALTER ROLE old_role_name RENAME TO new_role_name;

Be aware that renaming a role doesn't automatically update references in application code, connection strings, or permission grants.