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From Stefan Matheis <>
Subject Re: Question about external file fields
Date Fri, 06 Dec 2013 10:03:36 GMT
I guess you refer to this post?

If so .. he already provides at least one possible use case:


We use Solr to serve our company’s browse pages. Our browse pages are similar to how a typical
Stackoverflow tag page looks. That “browse” page has the question title (which links to
the actual page that contains the question, comments and replies), view count, snippet of
the question text, questioner’s profile info, tags and time information. One thing that
can change quite frequently on such a page is the view count. I believe Stackoverflow uses
Redis to keep track of the view counts, but we have to currently manage this in Solr, since
Solr is our only datastore to serve these browse pages.

The problem before Solr 4.0 was that you could not update a single field in a document. You
have to form the entire document first (either by querying Solr or using an alternate data
source which contains all the info), update the view count and then post the entire document
to Solr. With Solr 4+, you can do atomic update of a single field – the Solr server internally
handles fetching the entire document, updating the field and updating its index. But atomic
update comes with some caveats – you must store all your Solr fields (other than copyFields),
which can increase your storage space and enable updateLog, which can slow down Solr start-up.

For this specific problem of updating a field more frequently than the rest of the document,
external file fields (EFFs) can come in quite handy. They have one main restriction though
– you cannot use them in your queries directly i.e. they cannot be used in the q parameter
directly. But we will see how we can circumvent this problem at least partially using function
query hacks.


another case, out of my head, might be product pricing or updates on stock count.

- Stefan  

On Thursday, December 5, 2013 at 11:11 PM, yriveiro wrote:

> Hi,
> I read this post about EEF's and I
> found very interesting.
> Can someone give me more use cases about the utility of EEF's?
> /Yago
> -----
> Best regards
> --
> View this message in context:
> Sent from the Solr - User mailing list archive at (

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