Re: missing row form select for update

[Mikael Ronström]

SELECT FOR UPDATE means that all 4 rows will be locked exclusively.
Thus it is normal that other transactions that perform operations
that perform row locking will be blocked until the transaction is
completed.

The missing row problem is harder to analyse without more details.

From your description the SELECT is a range scan on an index. If the
value of the index columns are updated, the row will move inside the
index, this could cause a row to not be seen by another scan
if it moves from being
after scan cursor to be placed before scan cursor.