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https://issues.apache.org/jira/browse/SOLR-9166?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15655010#comment-15655010
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Erick Erickson commented on SOLR-9166:
--------------------------------------
Well, certainly not the final patch for 6x. Siiiggggh.
[~mikemccand][~jpountz][~rcmuir] (and others). Just to check what I think I'm
seeing...
In trunk, ExportWriter has a bunch of clauses like:
` NumericDocValues vals = DocValues.getNumeric(reader, this.field);
if (vals.advance(docId) == docId) {
val = vals.longValue();
} else {
val = 0;
}
ew.put(field, val);
'
but 6x just looks like:
` NumericDocValues vals = DocValues.getNumeric(reader, this.field);
long val = vals.get(docId);
ew.put(field, val);
`
and vals.get(docId) returns zero when a docValues field isn't in the document.
So my question is: "Would you agree that returning nothing rather than zero for
docValues fields that have no entry for a particular doc would require a lot of
work in 6x?"
I know there was a whole long discussion about this on the LUCENE Jira list
some time ago but the resolution kind of escapes me and the patch is huge.
Thanks.
> Export handler returns zero for numeric fields that are not in the original
> doc
> -------------------------------------------------------------------------------
>
> Key: SOLR-9166
> URL: https://issues.apache.org/jira/browse/SOLR-9166
> Project: Solr
> Issue Type: Bug
> Reporter: Erick Erickson
> Assignee: Rohit
> Attachments: SOLR-9166.patch, SOLR-9166.patch, SOLR-9166.patch,
> SOLR-9166.patch
>
>
> From the dev list discussion:
> My original post.
> Zero is different from not
> existing. And let's claim that I want to process a stream and, say,
> facet on in integer field over the result set. There's no way on the
> client side to distinguish between a document that has a zero in the
> field and one that didn't have the field in the first place so I'll
> over-count the zero bucket.
> From Dennis Gove:
> Is this true for non-numeric fields as well? I agree that this seems like a
> very bad thing.
> I can't imagine that a fix would cause a problem with Streaming Expressions,
> ParallelSQL, or other given that the /select handler is not returning 0 for
> these missing fields (the /select handler is the default handler for the
> Streaming API so if nulls were a problem I imagine we'd have already seen
> it).
> That said, within Streaming Expressions there is a select(...) function which
> supports a replace(...) operation which allows you to replace one value (or
> null) with some other value. If a 0 were necessary one could use a
> select(...) to replace null with 0 using an expression like this
> select(<stream>, replace(fieldA, null, withValue=0)).
> The end result of that would be that the field fieldA would never have a null
> value and for all tuples where a null value existed it would be replaced with
> 0.
> Details on the select function can be found at
> https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=61330338#StreamingExpressions-select.
> And to answer Denis' question, null gets returned for string DocValues fields.
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