> What happens if every query has an explicit list of fields to return in
> results, and the list of fields does NOT include this field that
> contains a large amount of data in docValues? Does this mean that the
> docValues data for the field I've mentioned is never read, and has no
> effect on OS disk cache efficiency?

That is my understanding.


On Fri, Jan 13, 2017 at 5:29 AM, Shawn Heisey <apa...@elyograg.org> wrote:

> I have an idea for a Solr feature, but to know whether it's at all
> viable, I need a question about Lucene operation answered.
>
> In recent versions of Solr, if a field is not stored, not indexed, but
> does have docValues, the originally indexed data sent for that field
> will be returned in search results.  In older versions (not sure which
> ones) a field must be stored to be returned.
>
> Let's say that such a field contains a very large amount of data in
> every document.  Normally, this would affect OS disk cache efficiency
> for general queries, because the docValues data for the field would need
> to be read in order to be included in search results.  Reading that
> large amount of data can pollute the disk cache.  If the system is in a
> low-memory situation, that can affect performance.
>
> What happens if every query has an explicit list of fields to return in
> results, and the list of fields does NOT include this field that
> contains a large amount of data in docValues?  Does this mean that the
> docValues data for the field I've mentioned is never read, and has no
> effect on OS disk cache efficiency?  Or would Lucene read the docValues
> data even though it doesn't include it in results?
>
> Thanks,
> Shawn
>
>
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