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https://issues.apache.org/jira/browse/SOLR-13199?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17056298#comment-17056298
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Munendra S N commented on SOLR-13199:
-------------------------------------
{code:java}
I suspect you are not familiar with how nested documents work and/or this
particular DocTransformer. The use-case for a child doc transformer is when
the master query matches only parent documents but you want to see their
children in the response, attached to it. What the user pages through are
parent documents; they only see parent documents.
{code}
I think I didn't explain the case properly.
Let's consider http://yonik.com/solr-nested-objects/ Suppose the initial query
is {{author_s:yonik}} which matches parent document and {{cat_s:fantasy}} is
the parentFilter used in childDocTranformer(child documents are reviews). This
works fine
Now say, we add a new book by {{author_s:yonik}} which belongs to
{{cat_s:biography}}. Once this is added, if a make same query
{{author_s:yoniik}} and {{parentFilter=cat_s:fantasy}}, new parentFilter won't
obviously match {{cat_s:biography}} and So, getBitSet will return {{null}} we
get NPE.
This is what I was trying to explain but made it complicated by introducing
pagination and etc.
I understand in this case better parentFilter would be type_s:book instead of
cat_s but in the beginning cat_s is also constant across the parent set until
new category is introduced.
After some more thought and trying to out scenarios like childless parent(which
works fine as long parentFilter is proper), it is better to fail the request
instead of not returning any children since parent contains children but not
able to return because of improper parentFilter
I will make changes to throw an error in both cases.
[~dsmiley] Thanks a lot for your patience and detailed explanation
> NPE due to unexpected null return value from QueryBitSetProducer.getBitSet
> --------------------------------------------------------------------------
>
> Key: SOLR-13199
> URL: https://issues.apache.org/jira/browse/SOLR-13199
> Project: Solr
> Issue Type: Bug
> Components: search
> Affects Versions: master (9.0)
> Environment: h1. Steps to reproduce
> * Use a Linux machine.
> * Build commit {{ea2c8ba}} of Solr as described in the section below.
> * Build the films collection as described below.
> * Start the server using the command {{./bin/solr start -f -p 8983 -s
> /tmp/home}}
> * Request the URL given in the bug description.
> h1. Compiling the server
> {noformat}
> git clone https://github.com/apache/lucene-solr
> cd lucene-solr
> git checkout ea2c8ba
> ant compile
> cd solr
> ant server
> {noformat}
> h1. Building the collection
> We followed [Exercise
> 2|http://lucene.apache.org/solr/guide/7_5/solr-tutorial.html#exercise-2] from
> the [Solr
> Tutorial|http://lucene.apache.org/solr/guide/7_5/solr-tutorial.html]. The
> attached file ({{home.zip}}) gives the contents of folder {{/tmp/home}} that
> you will obtain by following the steps below:
> {noformat}
> mkdir -p /tmp/home
> echo '<?xml version="1.0" encoding="UTF-8" ?><solr></solr>' >
> /tmp/home/solr.xml
> {noformat}
> In one terminal start a Solr instance in foreground:
> {noformat}
> ./bin/solr start -f -p 8983 -s /tmp/home
> {noformat}
> In another terminal, create a collection of movies, with no shards and no
> replication, and initialize it:
> {noformat}
> bin/solr create -c films
> curl -X POST -H 'Content-type:application/json' --data-binary '{"add-field":
> {"name":"name", "type":"text_general", "multiValued":false, "stored":true}}'
> http://localhost:8983/solr/films/schema
> curl -X POST -H 'Content-type:application/json' --data-binary
> '{"add-copy-field" : {"source":"*","dest":"_text_"}}'
> http://localhost:8983/solr/films/schema
> ./bin/post -c films example/films/films.json
> {noformat}
> Reporter: Johannes Kloos
> Assignee: Munendra S N
> Priority: Minor
> Labels: diffblue, newdev
> Attachments: SOLR-13199.patch, home.zip
>
>
> Requesting the following URL causes Solr to return an HTTP 500 error response:
> {noformat}
> http://localhost:8983/solr/films/select?fl=[child%20parentFilter=ge]&q=*:*
> {noformat}
> The error response seems to be caused by the following uncaught exception:
> {noformat}
> java.lang.NullPointerException
> at
> org.apache.solr.response.transform.ChildDocTransformer.transform(ChildDocTransformer.java:92)
> at org.apache.solr.response.DocsStreamer.next(DocsStreamer.java:103)
> at org.apache.solr.response.DocsStreamer.next(DocsStreamer.java:1)
> at
> org.apache.solr.response.TextResponseWriter.writeDocuments(TextResponseWriter.java:184)
> at
> org.apache.solr.response.TextResponseWriter.writeVal(TextResponseWriter.java:136)
> at
> org.apache.solr.common.util.JsonTextWriter.writeNamedListAsMapWithDups(JsonTextWriter.java:386)
> at
> org.apache.solr.common.util.JsonTextWriter.writeNamedList(JsonTextWriter.java:292)
> at org.apache.solr.response.JSONWriter.writeResponse(JSONWriter.java:73)
> {noformat}
> In ChildDocTransformer.transform, we have the following lines:
> {noformat}
> final BitSet segParentsBitSet = parentsFilter.getBitSet(leafReaderContext);
> final int segPrevRootId = segRootId==0? -1:
> segParentsBitSet.prevSetBit(segRootId - 1); // can return -1 and that's okay
> {noformat}
> But getBitSet can return null if the set of DocIds is empty:
> {noformat}
> return docIdSet == DocIdSet.EMPTY ? null : ((BitDocIdSet) docIdSet).bits();
> {noformat}
> We found this bug using [Diffblue Microservices
> Testing|https://www.diffblue.com/labs/?utm_source=solr-br]. Find more
> information on this [fuzz testing
> campaign|https://www.diffblue.com/blog/2018/12/19/diffblue-microservice-testing-a-sneak-peek-at-our-early-product-and-results?utm_source=solr-br].
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