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https://issues.apache.org/jira/browse/SOLR-3855?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13493138#comment-13493138
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Adrien Grand commented on SOLR-3855:
------------------------------------
{quote}
Regarding performance - it seems like for most users, the number of docvalue
fields should be relatively small.
One of the big advantages to DocValues is the better caching by the OS - so
"seeks" should often never hit the disk.
{quote}
I agree that it is unlikely to affect performance for many users but on the
other hand I don't like the fact that Solr could suddenly get insanely slow if
doc values fields grow larger than the size of the I/O cache.
bq. stored=[docValues method] // store separately using the given method
I'm afraid it could be confusing for users: doc values are very different from
stored fields feature-wise (sorting, function values) and performance-wise (up
to 1 seek per doc vs. up to 1 seek per field) so I think we should use another
parameter name?
bq. But it seems like that should just be a default and one should be able to
access the field via direct or memory depending on the situation?
To avoid surprises (OOM on the one hand / extreme slowness on the other hand) I
think we should stick to an explicit access method specified in the schema?
(I've planned to fix SortField/FieldComparator so that it doesn't force doc
values to be memory-resident when sorting.)
The question of loading or not doc values fields by default seems to raise lots
of concerns. Maybe we should fix this issue with no promise that doc values
fields would be loaded by default and open another issue to find out whether it
is reasonable or not to do so? (I'm just afraid that consensus might be hard to
obtain while everyone seems to agree that DocValues support is an improvement?)
> DocValues support
> -----------------
>
> Key: SOLR-3855
> URL: https://issues.apache.org/jira/browse/SOLR-3855
> Project: Solr
> Issue Type: Improvement
> Reporter: Adrien Grand
> Assignee: Adrien Grand
> Priority: Minor
> Fix For: 4.1, 5.0
>
> Attachments: SOLR-3855.patch, SOLR-3855.patch
>
>
> It would be nice if Solr supported DocValues:
> - for ID fields (fewer disk seeks when running distributed search),
> - for sorting/faceting/function queries (faster warmup time than fieldcache),
> - better on-disk and in-memory efficiency (you can use packed impls).
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