| From: | Atri Sharma <atri(dot)jiit(at)gmail(dot)com> |
|---|---|
| To: | Tomas Vondra <tv(at)fuzzy(dot)cz> |
| Cc: | Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Re: custom hash-based COUNT(DISTINCT) aggregate - unexpectedly high memory consumption |
| Date: | 2013-10-08 04:23:37 |
| Message-ID: | CAOeZVicWD9a-FV2ZZnjO=2vV-ch5QAOijV6KjVdH994CAn07hw@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hi Tomas,
>> Consider the aspects associated with open addressing.Open addressing
>> can quickly lead to growth in the main table.Also, chaining is a much
>> cleaner way of collision resolution,IMHO.
>
> What do you mean by "growth in the main table"?
Sorry, I should have been more verbose.
AFAIK, Open addressing can be slower with a load factor approaching 1
as compared to chaining. Also, I feel that implementation of open
addressing can be more complicated as we have to deal with deletes
etc.
I feel we can redesign our current chaining mechanism to have skip
lists instead of singly linked lists. I experimented with it sometime
back and I feel that it gives a stable performance with higher loads.
Regards,
Atri
--
Regards,
Atri
l'apprenant
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