Parallel updates on multiple cores

I have the following case: a simple table<br /><br />drop table test_data;<br />create table test_data (<br />id
bigserialnot null primary key,<br />content varchar(50),<br />processed varchar(1)<br />);<br /><br />My function doing
theinserts<br /><br />CREATE OR REPLACE FUNCTION populate_test_data(IN nr_records BIGINT, IN proc_nr BIGINT) RETURNS
integerAS $$<br />DECLARE<br />    counter BIGINT := 0;<br />    record_val text;<br />BEGIN<br />LOOP    <br />  
 counter:=counter+1;<br/>    record_val:=((('v ' || counter) || ' p ') || proc_nr);<br />    insert into
test_data(content,processed) values(record_val,'n');<br />    EXIT WHEN counter > nr_records;<br />END LOOP;<br
/>RETURN0;<br />END;<br />$$ LANGUAGE plpgsql;<br /><br />where nr_records represents the number of inserts, and<br
/><br/>CREATE OR REPLACE FUNCTION select_unprocessed(IN start_id BIGINT, IN end_id BIGINT) RETURNS integer AS $$<br
/>DECLARE<br/>    counter BIGINT := 0;<br />    record_val text;<br />    rec record;<br /><br />BEGIN<br />FOR rec IN
SELECTid, content, processed FROM test_data WHERE id >= start_id AND id < end_id<br />LOOP        <br />  
 record_val:=rec.content|| '-DONE-';<br />    update test_data set content=record_val, processed='n' where
id=rec.id;<br/>END LOOP;<br />RETURN 0;<br /><br />END;<br />$$ LANGUAGE plpgsql;<br /><br />The function above updates
therows between the ids start_id and end_id.<br />I have a quad core procesor so i run two separate connections to the
database:select populate_test_data(5000,1) and another select populate_test_data(5000,2). In this case each function
runson one core doing the inserts in parallel, but when i try to run select select_unprocessed(1,5001) and from another
connectionselect select_unprocessed(5001, 10001), one of the processes locks the table so the other one has to wait
untilthe table is unlocked.<br />Each process updates different parts of the table.<br />Is there a way to do the
updatesin parallel on multiple cores?<p>