The generated buffer is 140MB, not 14MB. At 14 bytes per row, that makes
sense.
I have done another test.
If I execute `FETCH ALL FROM cursor` I get a 140MB disk buffer file, on the
PostgreSQL server, reported in its log.
If I execute `FETCH 5000000 FROM cursor` (exactly half the rows), I see a
70MB disk buffer file.
This is regardless of how many rows I actually stream from thE connection
before closing the cursor.