On Wed, 2007-02-28 at 11:09 -0500, Tom Lane wrote: > "Simon Riggs" <[EMAIL PROTECTED]> writes: > > VACUUM's current behaviour is to take blocks it has touched and place > > them on the head of the freelist, allowing them to be reused. > > No, it puts them at the tail of the freelist.
That's a minor point because the freelist is mostly empty, so head == tail in 99.9% of cases. The freelist does start full, but we only *put* things on the freelist when we call InvalidateBuffer() after a DROP TABLE etc, or when we finish with a VACUUM buffer. So after the first few minutes of server operation we hardly ever use the freelist and so will be empty when we start dropping VACUUM'd buffers on it, head or tail. The negative effect on response times and overall performance is clearly noticeable in tests. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
