Re: Data Warehouse Reevaluation - MySQL vs Postgres --

>> insert into X
>>   select a.keyA,
>>          a.keyB,
>>      a.colA,
>>      a.colB
>>   from Y a left join X b
>>        using (keyA, keyB)
>>   where b.keyA is NULL and
>>         b.keyB is NULL;
>>
>> With the appropriate indexes, this is pretty fast but I think a merge
>> would be much faster.

Problem is it's subject to race conditions if another process is 
inserting stuff at the same time...

Chris