On 01/05/2020 05:20, James Coleman wrote:
On Tue, Apr 28, 2020 at 8:25 AM Tomas Vondra
<tomas.von...@2ndquadrant.com> wrote:
...
Any particular reasons to pick dynahash over simplehash? ISTM we're
using simplehash elsewhere in the executor (grouping, tidbitmap, ...),
while there are not many places using dynahash for simple short-lived
hash tables. Of course, that alone is a weak reason to insist on using
simplehash here, but I suppose there were reasons for not using dynahash
and we'll end up facing the same issues here.
I've attached a patch series that includes switching to simplehash.
Obviously we'd really just collapse all of these patches, but it's
perhaps interesting to see the changes required to use each style
(binary search, dynahash, simplehash).
As before, there are clearly comments and naming things to be
addressed, but the implementation should be reasonably clean.
Looks good, aside from the cleanup work that you mentioned. There are a
few more cases that I think you could easily handle with very little
extra code:
You could also apply the optimization for non-Const expressions, as long
as they're stable (i.e. !contain_volatile_functions(expr)).
Deconstructing the array Datum into a simple C array on first call would
be a win even for very small arrays and for AND semantics, even if you
don't use a hash table.
- Heikki
