Hoss Man created SOLR-7631:
------------------------------
Summary: Faceting on multivalued Trie fields with precisionStep !=
0 can produce bogus value="0" in some situations
Key: SOLR-7631
URL: https://issues.apache.org/jira/browse/SOLR-7631
Project: Solr
Issue Type: Bug
Reporter: Hoss Man
Working through SOLR-7605, I've confirmed that the underlying problem exists
for regular {{field.facet}} situations, regardless of distrib mode, for Trie
fields that have a non-zero precisionStep -- there's still ome other missing
piece of the puzzle i haven't figured out, but it relates in some way to some
of randomized factors we use in our tests (Codec? PostingFormat? ... no idea)
The problem, when it manifests, is that faceting on a TrieIntField, using
{{facet.mincount=0}}, causes the facet results to include three instances of
facet the value "0" listed with a count of "0" -- even though no document in
the index contains this value at all...
{noformat}
[junit4] > <lst name="facet_fields">
[junit4] > <lst name="foo_ti">
[junit4] > <int name="20">32</int>
...
[junit4] > <int name="50">21</int>
[junit4] > <int name="0">0</int>
[junit4] > <int name="0">0</int>
[junit4] > <int name="0">0</int>
{noformat}
This is concerning for a few reasons:
* In the case of PivotFaceting, getting duplicate values back from a single
shard like this triggers an assert in distributed queries and the request fails
-- even if asserts aren't enabled, the bogus "0" value can be propogated to
clients if they ask for facet.pivot.mincount=0
* Client code expecting a single (value,count) pair for each value may equally
be confused/broken by this response where the same "value" is returned multiple
times
* w/o knowing the root cause, It seems very possible that other nonsense values
may be getting returned -- ie: if the error only happens with fields utilizing
precisionStep, then it's likely related to the synthetic values used for faster
range queries, and other synthetic values may be getting included with bogus
counts
A Patch with a simple test that can demonstrate the bug fairly easily will be
attached shortly
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