Обсуждение: Modyfication Sort Merge Join Alghoritm
Hi users.
I want to sure, that is no this implementation in Postgresql:
For Sorte Merge Join Alghoritm:
If the large input arrives sorted,
g-join joins its pages with the buffer pool contents by strictly
increasing join key values and the join output is also strictly
sorted.
Is it difficult to implement this functionality?
Best Regards,
Tom
I want to sure, that is no this implementation in Postgresql:
For Sorte Merge Join Alghoritm:
If the large input arrives sorted,
g-join joins its pages with the buffer pool contents by strictly
increasing join key values and the join output is also strictly
sorted.
Is it difficult to implement this functionality?
Best Regards,
Tom
On 08/12/2013 01:31 PM, tubadzin wrote: > Hi users. > I want to sure, that is no this implementation in Postgresql: > For Sorte Merge Join Alghoritm: > If the large input arrives sorted, > g-join joins its pages with the buffer pool contents by strictly > increasing join key values and the join output is also strictly > sorted. I'm not quite sure what you're asking. We have a merge sort already, and AFAIK it doesn't resort the input if it was sorted in an earlier step. -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com
On Mon, Aug 12, 2013 at 1:31 PM, tubadzin <tubadzin@o2.pl> wrote: > Hi users. > I want to sure, that is no this implementation in Postgresql: > For Sorte Merge Join Alghoritm: > If the large input arrives sorted, > g-join joins its pages with the buffer pool contents by strictly > increasing join key values and the join output is also strictly > sorted. What is a "g-join"? If you have a reference to that algorithm, it would help clarify what you are asking. Cheers, Jeff
On Mon, Aug 12, 2013 at 08:16:59PM -0700, Jeff Janes wrote: > On Mon, Aug 12, 2013 at 1:31 PM, tubadzin <tubadzin@o2.pl> wrote: > > Hi users. > > I want to sure, that is no this implementation in Postgresql: > > For Sorte Merge Join Alghoritm: > > If the large input arrives sorted, > > g-join joins its pages with the buffer pool contents by strictly > > increasing join key values and the join output is also strictly > > sorted. > > What is a "g-join"? If you have a reference to that algorithm, it > would help clarify what you are asking. There's a paper that includes the phrase "g-join" from 2011 here: http://wwwlgis.informatik.uni-kl.de/cms/fileadmin/users/haerder/2011/JoinAndGrouping.pdf Is that it? Cheers, David. -- David Fetter <david@fetter.org> http://fetter.org/ Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter Skype: davidfetter XMPP: david.fetter@gmail.com iCal: webcal://www.tripit.com/feed/ical/people/david74/tripit.ics Remember to vote! Consider donating to Postgres: http://www.postgresql.org/about/donate