Grzegorz Jaskiewicz <[EMAIL PROTECTED]> writes:
> On Mar 5, 2007, at 2:36 AM, Tom Lane wrote:
>> I'm also less than convinced that it'd be helpful for a big seqscan:
>> won't reading a new disk page into memory via DMA cause that memory to
>> get flushed from the processor cache anyway?

> Nope. DMA is writing directly into main memory. If the area was in  
> the L2/L1 cache, it will get invalidated. But if it isn't there, it  
> is okay.

So either way, it isn't in processor cache after the read.  So how can
there be any performance benefit?

                        regards, tom lane

---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
       choose an index scan if your joining column's datatypes do not

Reply via email to