Re: Re: custom hash-based COUNT(DISTINCT) aggregate - unexpectedly high memory consumption - Mailing list pgsql-hackers

From Tomas Vondra
Subject Re: Re: custom hash-based COUNT(DISTINCT) aggregate - unexpectedly high memory consumption
Date
Msg-id 5253215C.1050500@fuzzy.cz
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In response to Re: Re: custom hash-based COUNT(DISTINCT) aggregate - unexpectedly high memory consumption  (Atri Sharma <atri.jiit@gmail.com>)
Responses Re: Re: custom hash-based COUNT(DISTINCT) aggregate - unexpectedly high memory consumption  (Atri Sharma <atri.jiit@gmail.com>)
List pgsql-hackers
Hi Atri!

On 7.10.2013 16:56, Atri Sharma wrote:
>>> 3. Consider dropping buckets in favor of open addressing (linear
>>> probing, quadratic, whatever).  This avoids another level of
>>> pointer indirection.
>> 
>> OK, this sounds really interesting. It should be fairly
>> straightforward for fixed-length data types (in that case I can get
>> rid of the pointers altogether).
>> 
> 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"?

Tomas



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