Thread: What Index Access Method Functions are really needed?
Hi, another question regarding indexes. Sadly I can't find enough info in the documentation. Which of the functions are needed in order for a index to work? I am developing a prototype so it would be great if not all of the functions have to be implemented. E.g. are amcostestimate or amoptions needed? Greets, Yves
Yves Weißig <weissig@rbg.informatik.tu-darmstadt.de> writes:
> another question regarding indexes. Sadly I can't find enough info in
> the documentation. Which of the functions are needed in order for a
> index to work?
All of them.
regards, tom lane
> > another question regarding indexes. Sadly I can't find enough info in > > the documentation. Which of the functions are needed in order for a > > index to work? > > All of them. Maybe I completely misunderstood the question, but some functions are "optionals", such as amgetbitmap, right? http://www.postgresql.org/docs/9.0/static/index-functions.html
Leonardo Francalanci <m_lists@yahoo.it> wrote: >>> another question regarding indexes. Sadly I can't find enough >>> info in the documentation. Which of the functions are needed in >>> order for a index to work? >> >> All of them. > > > Maybe I completely misunderstood the question, but some functions > are "optionals", such as amgetbitmap, right? > > http://www.postgresql.org/docs/9.0/static/index-functions.html Browsing that page, I think these are the two relevant bits regarding exceptions to the rule: | The amgettuple function need only be provided if the access method | supports "plain" index scans. If it doesn't, the amgettuple field | in its pg_am row must be set to zero. | The amgetbitmap function need only be provided if the access | method supports "bitmap" index scans. If it doesn't, the | amgetbitmap field in its pg_am row must be set to zero. I have no idea which of these would be useful for the AM being discussed. -Kevin
That is exactly the point, Kevin, I read the documentation and found out that "amgettuple" and "amgetbitmap" are optional. I just wondered if there is more information about this topic? Additionally, I can not find "amcostestimate" in hash.h or anywhere, or am I missing something? So "All of them" lacks some exceptions, or? Am 22.04.2011 17:27, schrieb Kevin Grittner: > Leonardo Francalanci <m_lists@yahoo.it> wrote: >>>> another question regarding indexes. Sadly I can't find enough >>>> info in the documentation. Which of the functions are needed in >>>> order for a index to work? >>> >>> All of them. >> >> >> Maybe I completely misunderstood the question, but some functions >> are "optionals", such as amgetbitmap, right? >> >> http://www.postgresql.org/docs/9.0/static/index-functions.html > > Browsing that page, I think these are the two relevant bits > regarding exceptions to the rule: > > | The amgettuple function need only be provided if the access method > | supports "plain" index scans. If it doesn't, the amgettuple field > | in its pg_am row must be set to zero. > > | The amgetbitmap function need only be provided if the access > | method supports "bitmap" index scans. If it doesn't, the > | amgetbitmap field in its pg_am row must be set to zero. > > I have no idea which of these would be useful for the AM being > discussed. > > -Kevin >