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 match