[jira] [Commented] (SOLR-9166) Export handler returns zero for fields numeric fields that are not in the original doc

["Erick Erickson (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-9166?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15304196#comment-15304196 ] 

Erick Erickson commented on SOLR-9166:
--------------------------------------

From Joel on the dev list.

Yes, the /export handler returns zero for numeric fields that aren't present. String fields should be empty though if not present.

We'll want to keep the zero while sorting in the /export handler. But removing the zero when outputing the field should by OK. We'll just need to add test cases that cover the numeric nulls. The RollupStream would be one place that might have a problem with this.

Also, there may be other client applications that rely on the current behavior. So possibly adding a switch on the export handler for numeric nulls is the safest approach.



> Export handler returns zero for fields 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: Erick Erickson
>
> 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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