Suppose I have the following trivial code:

```sql
BEGIN;
WITH foo AS (SELECT * FROM t1),
     bar AS (SELECT * FROM t1)
SELECT * FROM foo, bar;
COMMIT;

```

The isolation level will be, [by default, `READ-COMMITTED`](https://www.postgresql.org/docs/9.1/transaction-iso.html#XACT-READ-COMMITTED). This of course means if you had two separate selects you could (in theory) have non-repeatable reads.

My question is: in the example code, do these two different selects count as a single read-committed command, or is each select on its own, making it possible for both to (in theory) see different rows?