During repacking table, if a transaction executes INSERT CONFLICT
ON UPDATE/DO NOTHING, because we define BEFORE trigger on target
table, the contents of operation log table becomes inconsistent
easliy. As a result, pg_reapck fails with a high probability.
To resolve this issue, this changes the trigger type from BEFORE
to AFTER. We define AFTER trigger that is the first of the AFTER
trigger to fire on the table.
