Re: Proposal: scan key push down to heap [WIP]

On 2016-10-25 13:18:47 -0400, Tom Lane wrote:
> (Frankly, I'm pretty skeptical of this entire patch being worth the
> trouble...)

The gains are quite noticeable in some cases. So if we can make it work
without noticeable downsides...

What I'm worried about though is that this, afaics, will quite
noticeably *increase* total cost in cases with a noticeable number of
columns and a not that selective qual. The reason for that being that
HeapKeyTest() uses heap_getattr(), whereas upper layers use
slot_getattr(). The latter "caches" repeated deforms, the former
doesn't... That'll lead to deforming being essentially done twice, and
it's quite often already a major cost of query processing.