Обсуждение: 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
>