Re: Question about RUM-index

On Fri, Jun 17, 2016 at 9:32 AM, Andreas Joseph Krogh <andreas(at)visena(dot)com>
wrote:

> På torsdag 16. juni 2016 kl. 00:50:45, skrev Jeff Janes <
> jeff(dot)janes(at)gmail(dot)com>:
>
> On Wed, Jun 15, 2016 at 3:56 AM, Andreas Joseph Krogh <andreas(at)visena(dot)com>
> wrote:
>>
>> Hi.
>>
>> First; Is this the correct forum to ask questions about the Postgres
>> Pro's new RUM-index?
>>
>> If not, please point me to the right forum.
>>
>
> I think that https://github.com/postgrespro/rum/issues might be the best
> forum.
>
>
> Oleg and friends; Should we use GitHub-issues as forum (one issue per
> question/thread?), pgsql-general or something else?
>

Andreas,

we are hardly working on our internal version of rum and will open it after
resolving some issues. I think the best place to discuss it is -hackers.

>
>
> Note that GIN does almost what I want, except use the index when sorting
>> by "sent"-timestamp.
>>
>> So I wonder if RUM can do any better?
>> What I don't understand is how to have "folder_id" as part of the
>> RUM-index so that I can search in *an array* of folders using the index,
>> *AND* have the whole result sorted by "sent"-timestamp also using the
>> RUM-index.
>>
>
> I think you would have to implement an operator for integers for RUM much
> like btree_gin does for GIN. Sorry don't know how to do that, except to
> say look in the RUM code to see how it does it for time-stamps.
>
>
>>
>> In the (limited) documentation sorting using timestamp is done like this:
>>
>> ORDER BY sent <-> '2000-01-01'::TIMESTAMP
>>
>> which I don't understand; Why must one specify a value here, and how does
>> that value affect the result?
>>
>
>
> This is essentially identical to ORDER BY ABS(sent -
> '2000-01-01'::TIMESTAMP); except it can use the index.
>
> So maybe pick a constant outside the range of possible values, and use
> that as one argument to <->.
>
>
> This should be unnecessary and hidden from the user. Maybe some "ORDER BY
> rum_timestamp(sent)" or something could abstract away stuff to make it much
> clearer to the user?
> --
> *Andreas Joseph Krogh*
> CTO / Partner - Visena AS
> Mobile: +47 909 56 963
> andreas(at)visena(dot)com
> www.visena.com
> <https://www.visena.com>
>
>