[Xapian-discuss] questions about valuerangeprocessor and RefCntBase(edit and send again)

[白俊良]

Hi!  Alls

As Charlie said that my questions are hard to understand,i try to rephrase them.
Once you have time, please give me a help.

Indeed, I care more about how Xapian works.And I want to learn how  search engine works and how to design or  optimize a search engine.

I realized that some basic concept/classes,such as RefCntBase, internal  and Stats, are very important. But i can not make clear that why Xapian need them.In another word, i can not find out how Xapian work with them.

For example,i see that RefCntBase is a base class for objects which Xapian reference count,but i can not know the purpose that Xapian count reference,which is something i still want to know.
Simply,why Xapian needs reference count ?


Another question is about ValueRangeProcessor. 
I have read this:
http://xapian.org/docs/valueranges.html

Xapian::DateValueRangeProcessor date_proc(2, true, 1930); 
qp.add_valuerangeprocessor(&date_proc); 
    these was added in my code and it works perfectly.
I input the query"20090416..20090419", and I use query.get_description() to get the description "Parsed query is: Xapian::Query(VALUE_RANGE 2 20090216 20090219)".

Then, i wonder that how Xapian works it out.I can't see a detailed description of the OP_VALUE_* query operators anywhere.
Does Xapian rebuilt my query into 20090416,20090417,20090418
 20090419 and retrieval them separately ?
Or,it find start '20090416' and end '20090219' in the Btree,then return all the documents between them?
 
In another word, How does Xapian work while search value in Btree? And what is the difference between using value or not while search?

Generally speaking,i want to now how "valuerangesearch" works. Whether it only search in field "Value" or not? 
 

I have also read  this:
http://xapian.org/docs/matcherdesign.html
 
I can not find any word about ValueRangeProcessor, or "ValueRangePostList".
Then, how does the PostList Tree was design with RangeProcessor?
 


Regards,

baijl
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