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

From Claudio Freire
Subject Re: Re: custom hash-based COUNT(DISTINCT) aggregate - unexpectedly high memory consumption
Date
Msg-id CAGTBQpbRg4tabkvEFu2gb=Aiv67uhnHzYsMgykTArGeTxRKQpw@mail.gmail.com
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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>)
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On Tue, Oct 8, 2013 at 1:23 AM, Atri Sharma <atri.jiit@gmail.com> wrote:
>>> 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.


Deletes for a hash aggregate?

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