Commit every N rows in PL/pgsql

Hi,

I need to populate a new column in a Postgres 8.3 table. The SQL would be
something like "update t set col_c = col_a + col_b". Unfortunately, this
table has 110 million rows, so running that query runs out of memory.
In Oracle, I'd turn auto-commit off and write a pl/sql procedure that keeps
a counter and commits every 10000 rows (pseudocode):

define cursor curs as select col_a from t
while fetch_from_cursor(curs) into a
update t set col_c = col_a + col_b where col_a = a
i++
if i > 10000
commit; i=0;
end if;
commit;

PL/pgsql doesn't allow that because it doesn't support nested transactions.
Is there an equivalent Postgres way of doing this?

cheers,
Len
--
len(dot)walter(at)gmail(dot)com skype:lenwalter
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