Re: Heap WARM Tuples - Design Draft

On Fri, Aug  5, 2016 at 07:51:05PM -0300, Claudio Freire wrote:
> > This does create more HOT chains where the root ctid cannot be removed,
> > but it does avoid the index key/ctid check because any entry in the HOT
> > chain has identical keys.  What this would not handle is when an entire
> > HOT chain is pruned, as the keys would be gone.
> 
> I believe the only solution is to use bitmap index scans with WARM indexes.

Let me back up and explain the benefits we get from allowing HOT chains
to be WARM:

*  no index entries for WARM indexes whose values don't change
*  improved pruning because the HOT/WARM chains can be longer because we  don't have to break chains for index changes

While I realize bitmap indexes would allow us to remove duplicate index
entries, it removes one of the two benefits of WARM, and it causes every
index read to be expensive --- I can't see how this would be a win over
doing the index check on writes.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com

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