[SOLR-13199] NPE due to unexpected null return value from QueryBitSetProducer.getBitSet

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 9.0
• Fix Version/s: 8.6
• Component/s: search
• Labels: diffblue newdev

Environment

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.

Compiling the server

git clone https://github.com/apache/lucene-solr
cd lucene-solr
git checkout ea2c8ba
ant compile
cd solr
ant server

Building the collection

We followed Exercise 2 from the Solr Tutorial. The attached file (home.zip) gives the contents of folder /tmp/home that you will obtain by following the steps below:

mkdir -p /tmp/home
echo '<?xml version="1.0" encoding="UTF-8" ?><solr></solr>' > /tmp/home/solr.xml

In one terminal start a Solr instance in foreground:

./bin/solr start -f -p 8983 -s /tmp/home

In another terminal, create a collection of movies, with no shards and no replication, and initialize it:

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

• Assignee: Munendra S N
• Reporter: Johannes Kloos
• Created: 31/Jan/19 11:45
• Updated: 15/Jul/20 15:10
• Resolved: 18/Mar/20 05:49

Description

Requesting the following URL causes Solr to return an HTTP 500 error response:

http://localhost:8983/solr/films/select?fl=[child%20parentFilter=ge]&q=*:*

The error response seems to be caused by the following uncaught exception:

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)

In ChildDocTransformer.transform, we have the following lines:

final BitSet segParentsBitSet = parentsFilter.getBitSet(leafReaderContext);
final int segPrevRootId = segRootId==0? -1: segParentsBitSet.prevSetBit(segRootId - 1); // can return -1 and that's okay

But getBitSet can return null if the set of DocIds is empty:

return docIdSet == DocIdSet.EMPTY ? null : ((BitDocIdSet) docIdSet).bits();

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