Re: Fwd: Clarification about HOT

On 11/5/07, Heikki Linnakangas <heikki@enterprisedb.com> wrote:

Gokulakannan Somasundaram wrote:
> I think pointer swinging is still about maintaining the HOT chain within a
> page. Actually i am thinking about continuing the HOT chain across pages.

AFAICS, pointer-swinging would be exactly the same on cross-page HOT
chains as same-page chains.

When i read pointer-swinging, it talks a lot about in-page updates, pointing to the latest tuple instead of oldest tuple and circular pointers etc. Maybe, if i am missing the post, which you are referring to, please correct me on the steps i am talking about.

This scheme, if implemented would avoid the use of HOT stub and avoids the need to go to index, even if some other indexes are getting updated/ even if the updated new tuple goes into a new page

a) Whenever we update, we will update only those indexes whose attributes are updated. So the index will point to the top of the HOT chain.
b) Whenever we Vacuum the index, we take a list of tids and check whether there are any index tuples pointing to it. If the Vacuumed tuple is a start of the HOT chain, then we will carry the next in-line HOT tuple when we goto Vacuum the index. If the next in-line also satisfies the Vacuum, it will carry with it the next in-line HOT tuple-id.

In this way, we will make sure the Index points to a live tuple after the Vacuum.

This will remove the in-page pruning exercises, but as i said already the cost of updates will go down a lot with normal indexes.