Обсуждение: A general Q about index

soroosh sardari wrote
> Hi
> 
> I want to know how an index is created and used.
> actually if you can show to me a simple start point, it would be great.
> 
> Regards,
> Soroosh Sardari

In the documentation there is a table of contents and listed on that table
is a section named "Indexes".

David J.




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David Johnston wrote
> 
> soroosh sardari wrote
>> Hi
>> 
>> I want to know how an index is created and used.
>> actually if you can show to me a simple start point, it would be great.
>> 
>> Regards,
>> Soroosh Sardari
> In the documentation there is a table of contents and listed on that table
> is a section named "Indexes".
> 
> David J.

Since you posted this to hacker you may mean you wish to know how to program
them as oppose to use them in SQL.  I have no clue to this regard.  If you
did mean "use in SQL" then the documentation is your friend and you also
should not have posted this question to -hackers but to -general instead;
probably should have posted there anyway to begin with and been more clear
as to what you mean by "created and used".

David J.




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On 07/16/2013 11:09 PM, soroosh sardari wrote:
> 
> Actually  I mean the index in the source code, I want to know how index
> is used in the backend for
> execution of some query.
> sorry my question is a bit ambiguous,
> I start to read "src/backend/access/index/genam.c", and I think maybe
> this file is not good way to start.
> let me write a bunch of question to illustrate my point,
> -How create an index for a table with specified field
> -How index is stored in a page
> -what module is responsible to fetch and swap out index pages
> -Is there a kind of abstract class for all variant of index?

Start with the documentation:

http://www.postgresql.org/docs/current/static/internals.html

particularly:

http://www.postgresql.org/docs/current/static/indexam.html
http://www.postgresql.org/docs/current/static/gist.html
http://www.postgresql.org/docs/current/static/catalog-pg-index.html
http://www.postgresql.org/docs/current/static/catalog-pg-am.html

That should give you the ground work to understand the source code a bit
better. Then feel free to return with specific questions you don't feel
are explained by the documentation or code comments and aren't obvious
from the code.
-- Craig Ringer                   http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services