CREATE INDEX receiving_item_delivered_received
ON receiving_item_delivered_received USING btree ( eventtype,
replenishmenttype, serial_no, eventtime DESC );
>
More work_mem as Tomas suggests, but also, the above index should find the
candidate rows by the first two keys, and then be able to skip the sort by
reading just that portion of the index that matches
eventtype='LineItemdetailsReceived'
and replenishmenttype = 'DC2SWARRANTY'