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For a PostgreSQL role that needs to look up objects in one schema without reading table rows, grant database CONNECT if needed and schema USAGE. Do not grant table- or column-level SELECT. Schema USAGE allows lookup of objects; it does not authorize reading their data.
Grant database access and schema lookup
Use a dedicated, non-superuser login role, or review an existing role’s attributes and memberships before using it. This example gives the role access to database appdb and permits lookup in schema app:
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CREATE ROLE schema_reader
LOGIN
NOSUPERUSER
NOCREATEDB
NOCREATEROLE
NOBYPASSRLS;
GRANT CONNECT ON DATABASE appdb TO schema_reader;
GRANT USAGE ON SCHEMA app TO schema_reader;Replace the database, schema, and role names with your own. The example assumes the role does not own objects and does not inherit memberships or other grants that independently provide access. Do not grant CREATE ON SCHEMA unless the role should be able to create objects there.
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What these privileges do—and do not do
| Privilege | What it permits | What it does not permit by itself |
|---|---|---|
CONNECT on a database |
Connecting to that database, subject to connection configuration such as pg_hba.conf. |
Reading table rows. |
USAGE on a schema |
Looking up objects in the schema, subject to each object’s own privilege requirements. | Reading rows or creating objects. |
SELECT on a table or selected columns |
Reading the permitted table data or columns. | — |
CREATE on a schema |
Creating objects in that schema. | Reading existing table rows. |
PostgreSQL’s privileges manual defines schema USAGE as permission to access objects in the schema, provided the objects’ own privilege requirements are met: PostgreSQL 18 privileges. Keep USAGE separate from SELECT: the role can be allowed to look up an object while still being denied access to its rows.
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What “inspect the schema” means in practice
A role can inspect some metadata without being able to query table contents, but metadata visibility is not a guarantee that every object name is hidden. PostgreSQL’s information schema contains views describing objects in the current database; for example, information_schema.schemata lists schemas the current user can access. System catalog queries may reveal object names even without schema USAGE. See the information schema documentation.
Therefore, treat this as a permission boundary for data access, not a promise of complete object-name secrecy. If your requirement is to conceal object names as well as table contents, test the specific metadata queries your user or tool will run.
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Audit effective privileges before relying on the boundary
The two grants above do not cancel access obtained by other routes. PostgreSQL roles can inherit privileges through membership, and privileges can be granted to PUBLIC. Ownership is also more powerful than an ordinary grant. Review the target role’s direct and inherited access, object ownership, and any grants to PUBLIC before treating it as unable to read data.
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SELECTgrants. A table-level grant remains effective even if a column privilege is revoked. - Check role memberships, since membership may confer access assigned to another role.
- Check whether the role owns a table or other object; do not make a schema-inspection role an owner.
- Check database and object grants to
PUBLIC. PostgreSQL 18 documents defaultPUBLICprivileges for databases that includeCONNECTandTEMPORARY; explicit grants and database history can change the effective situation.
After reviewing grants, connect as the actual role. Confirm it can perform the intended metadata inspection and that a representative SELECT against a protected table fails. This checks the effective permissions of that account rather than only the grants you intended to issue.
Keep future-object defaults separate from existing grants
ALTER DEFAULT PRIVILEGES affects objects created in the future; it does not change permissions on existing objects. Defaults are determined by the role that creates each object, and are not inherited from roles of which that creator is a member. Per-schema default privileges add to global defaults rather than replacing them. If you use defaults to manage future access, review the creating role’s defaults as well as current object grants. See ALTER DEFAULT PRIVILEGES.
Do not confuse schema inspection with read-only data access
If the role should read selected data, that is a different design: grant SELECT only on the intended tables or columns, and audit inherited and public grants. For the no-data-read requirement, omit those grants. The choice depends on the required access scope:
| Requirement | Grant approach | Rows readable? | Scope and timing |
|---|---|---|---|
| Look up objects in a schema without reading table data | CONNECT on the database as needed; USAGE on the schema; no table or column SELECT. |
No, assuming no other effective grant, membership, or ownership provides access. | Database and schema level; grants affect the existing scope to which they are applied. |
| Read selected data without changing it | Grant carefully scoped table- or column-level SELECT. |
Yes, for the granted tables or columns. | Table or column level; configure defaults separately if future objects need corresponding access. |
Also review search_path: it controls unqualified name resolution. Avoid giving a role untrusted CREATE access in schemas on its search path, since writable searched schemas can create security risks. See PostgreSQL schema documentation.
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