Re: init_sequence spill to hash table

From: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>
To: Andres Freund <andres(at)2ndquadrant(dot)com>
Cc: David Rowley <dgrowleyml(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: init_sequence spill to hash table
Date: 2013-11-15 12:25:10
Message-ID: 528612A6.2020407@vmware.com
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On 15.11.2013 12:44, Andres Freund wrote:
> On 2013-11-15 12:31:54 +0200, Heikki Linnakangas wrote:
>> On 15.11.2013 07:47, David Rowley wrote:
>>> On Fri, Nov 15, 2013 at 3:03 AM, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com
>>>> wrote
>>>>
>>>> I think that means that we should just completely replace the list with
>>>> the hash table. The difference with a small N is lost in noise, so there's
>>>> no point in keeping the list as a fast path for small N. That'll make the
>>>> patch somewhat simpler.
>>>
>>> Attached is a much more simple patch which gets rid of the initial linked
>>> list.
>>
>> Thanks, committed with minor copy-editing. I dialed down the initial size of
>> the hash table from 1000 to 16, that ought to be enough.
>
> I am slightly confused by the use of HASH_CONTEXT without setting
> ctl->hcxt, that works, but seems more like an accident.

Ugh. Accident indeed. Thanks, fixed!

- Heikki

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