Function exists_target 

pub fn exists_target(
    spec: &Value,
    default_schema: &str,
) -> Option<(String, String)>

The table _exists looks in, as (schema, table).

Hasura’s metadata writes the name two ways – _table: user and _table: {schema: public, name: user} – and its own corpus uses the first. An unqualified name is read in the schema of the table the permission is on, which is where a permission written without a schema means to look.