> On Jul 5, 2022, at 22:35, Matthias Apitz <guru@xxxxxxxxxxx> wrote: > Internally, in the DB layer, the read_where() builds the row list matching > the WHERE clause as a SCROLLED CURSOR of > > SELECT ctid, * FROM d01buch WHERE ... > > and each fetch() delivers the next row from this cursor. The functions > start_transaction() and end_transaction() do what their names suggest and > rewrite_actual_row() does a new SELECT based on the ctid of the actual row > > SELECT * FROM d01buch WHERE ctid = ... FOR UPDATE > ... > UPDATE ... On first glance, it appears that you are using the ctid as a primary key for a row, and that's highly not-recommended. The ctid is never intended to be stable in the database, as you have discovered. There are really no particular guarantees about ctid values being retained. I'd suggest having a proper primary key column on the table, and using that instead.
