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From "Erick Erickson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-8220) Read field from docValues for non stored fields
Date Thu, 24 Dec 2015 19:09:49 GMT

    [ https://issues.apache.org/jira/browse/SOLR-8220?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15071193#comment-15071193
] 

Erick Erickson commented on SOLR-8220:
--------------------------------------

When we do the docs, we do need to include a warning about ordering. multiValued fields are
returned in sorted order when returned from DV fields, not the original order, right?

Up until now, we've promised that multiValued fields are returned in the same order they were
inserted into the document so two MV fields can be treated like parallel arrays. This will
_not_ be true of DV fields that are multiValued, correct?

Suggested text would be something like:

"Returning stored fields from docValues (default in schema versions 1.6+) returns multiValued
fields in sorted order. If you require the older behavior of multiValued fields being returned
in the original insertion order, set useDocValuesAsStored="false" for the individual fields
or make sure your schema version is < 1.6. This does _not_ require re-indexing."



> Read field from docValues for non stored fields
> -----------------------------------------------
>
>                 Key: SOLR-8220
>                 URL: https://issues.apache.org/jira/browse/SOLR-8220
>             Project: Solr
>          Issue Type: Improvement
>            Reporter: Keith Laban
>         Attachments: SOLR-8220-5x.patch, SOLR-8220-ishan.patch, SOLR-8220-ishan.patch,
SOLR-8220-ishan.patch, SOLR-8220-ishan.patch, SOLR-8220.patch, SOLR-8220.patch, SOLR-8220.patch,
SOLR-8220.patch, SOLR-8220.patch, SOLR-8220.patch, SOLR-8220.patch, SOLR-8220.patch, SOLR-8220.patch,
SOLR-8220.patch, SOLR-8220.patch, SOLR-8220.patch, SOLR-8220.patch, SOLR-8220.patch, SOLR-8220.patch,
SOLR-8220.patch, SOLR-8220.patch, SOLR-8220.patch, SOLR-8220.patch, SOLR-8220.patch, SOLR-8220.patch,
SOLR-8220.patch
>
>
> Many times a value will be both stored="true" and docValues="true" which requires redundant
data to be stored on disk. Since reading from docValues is both efficient and a common practice
(facets, analytics, streaming, etc), reading values from docValues when a stored version of
the field does not exist would be a valuable disk usage optimization.
> The only caveat with this that I can see would be for multiValued fields as they would
always be returned sorted in the docValues approach. I believe this is a fair compromise.
> I've done a rough implementation for this as a field transform, but I think it should
live closer to where stored fields are loaded in the SolrIndexSearcher.
> Two open questions/observations:
> 1) There doesn't seem to be a standard way to read values for docValues, facets, analytics,
streaming, etc, all seem to be doing their own ways, perhaps some of this logic should be
centralized.
> 2) What will the API behavior be? (Below is my proposed implementation)
> Parameters for fl:
> - fl="docValueField"
>   -- return field from docValue if the field is not stored and in docValues, if the field
is stored return it from stored fields
> - fl="*"
>   -- return only stored fields
> - fl="+"
>    -- return stored fields and docValue fields
> 2a - would be easiest implementation and might be sufficient for a first pass. 2b - is
current behavior



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