lucene-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Michael Busch <>
Subject Re: Does LUCENE-831) "Complete overhaul of FieldCache API" provide fieldcache offloading to disk?
Date Fri, 18 Apr 2008 09:32:22 GMT
Chris Hostetter wrote:
> : But then the FieldCache is just starting to feel alot like column-stride
> : fields
> : (LUCENE-1231).
> that's what i've been thinking ... my goal with LUCENE-831 was to make it 
> easier to manage FieldCache and hopefully the norms[] as well particularly 
> in the case of reopen ... but with column-stride fields the need for both 
> of those might go away completely)

(moved to java-dev, java-user cc'd)

My goal is it not to get rid of the FieldCache by adding column-stride 
fields (CSF), but instead to make them the default source for the 

We should introduce an interface, named maybe FieldValueSource, that the 
new FieldCache implements, and also the CSF API. That has some advantages:
- Norms can be stored as CSF, and can be accessed using the 
FieldValueSource API. Then we can easily add an option to IndexReader 
whether to cache norms in memory (i. e. the new FieldCache) or not. When 
users have huge indexes on 32bit machines, where the norms would consume 
too much memory, they can disable caching them, of course search 
performance will suffer (but that's better than OutOfMemoryErrors)
- The function queries can use the FieldValueSource interface to 
retrieve the values (allowing us to get rid of function/ValueSource).
- Any consumer of the FieldValueSource does not have to care about 
whether or not values are cached and how. If performance is too slow and 
memory permits, caching can be enabled very easily.
- We will still support loading the fieldcache from the dictionary for 
backwards compatibility, but we should think about deprecating this and 
eventually get rid of it. We probably shouldn't add an implementation of 
FieldValueSource that reads from the dictionary, because performance 
would be terrible in the non-cached mode.


To unsubscribe, e-mail:
For additional commands, e-mail:

View raw message