If read_past_deleted is On (the default), sequential scans at isolation levels 1 and 2 skip uncommitted deleted rows. If Off,
sequential scans block on uncommitted deleted rows at isolation levels 1 and 2 (until the deleting transaction commits or
rolls back). This option changes server behavior at isolation levels 1 and 2.
For most purposes, this option should be left On. If set to Off, the blocking behavior depends on the plan chosen by the optimizer
(if there is an index that could possibly be used).