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From Alex vB <m...@avomberg.de>
Subject How are stored Fields/Payloads loaded
Date Mon, 28 Feb 2011 21:38:20 GMT
Hello everybody,

I am currently unsure how stored data is written and loaded from index. 
I want to store for every term of a document some binary data but only once
and not for every position! 
Therefore I am not sure if Payloads or stored Fields are the better solution
(Or the not implemented feature Column Stride Field).

As far as I know all fields of a document are loaded by Lucene during
search. With large stored fields this can be time consuming and therefore
exists the possibility to load specific fields with FieldSelector. Maybe I
could create for each term a stored Field (up to several thousand Fields!)
and read those fields depending on the query term. Is this a common
approach?
The other possibility (like I have implemented it at the moment) is to store
per term a payload but only on the first term position. Payloads are loaded
only if I retrieve them from a hit right? So my current posting list looks
like this:
http://lucene.472066.n3.nabble.com/file/n2598739/Payload.png 
Picture adapted from M. McCandless "Fun with Flex"

How will the feature Column Stride Field (or per-document field) work? It's
not clear for me what "per Document" exactly means for the posting list
entries. I think (hope :P) it works like this:
http://lucene.472066.n3.nabble.com/file/n2598739/CSD.png 
Picture adapted from M. McCandless "Fun with Flex"


Do I understand the Column Stride Field correct? What would give me the best
performance (Stored Field, Payload, CSD)? Are there other ways to retrieve
payloads during search than Spanquery (I would like to use a normal query
here)?

Regards
Alex

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