See how {{ org.hibernate.search.integrationtest.backend.tck.search.aggregation.SingleFieldAggregationBaseIT#multiValued }} is disabled due to {{ org.hibernate.search.integrationtest.backend.lucene.testsupport.util.LuceneTckBackendFeatures#aggregationsOnMultiValuedFields }} .
Before HSEARCH-3839, we couldn't even index multiple values for numeric fields in Lucene. After HSEARCH-3839, we can, but we pick a single value when aggregating, so aggregations are still incorrect.
Ideally, when counting documents per field value, multi-valued documents should be counted once per value that appears in the field. So if a single document has values {{ 1 }} and {{ 2 }} for a single field, it should increment the count for both {{ 1 }} and {{ 2 }} . At least that's what happens on Elasticsearch.
How to test the behavior on Elasticsearch:
{code}
curl -XDELETE -H "Content-Type: application/json" localhost:9200/mytest1/ 1>&2 2>/dev/null; curl -XPUT -H "Content-Type: application/json" localhost:9200/mytest1/\?pretty -d'{"mappings":{"properties":{"num":{"type":"integer" }}} }'
url curl -XPUT -H "Content-Type: application/json" localhost:9200/mytest1/_doc/1 -d'{"num":1}'
curl -XPUT -H "Content-Type: application/json" localhost:9200/mytest1/_doc/2 -d'{"num":[1,2]}'
curl -XPOST -H "Content-Type: application/json" localhost:9200/mytest1/_search\?pretty -d'{"aggs":{"foo":{"terms":{"field":"num" }}} }'
{code}
Result:
{noformat}
{
...
"aggregations" : {
"foo" : {
"doc_count_error_upper_bound" : 0,
"sum_other_doc_count" : 0,
"buckets" : [
{
"key" : 1,
"doc_count" : 2
},
{
"key" : 2,
"doc_count" : 1
}
]
}
}
}
{noformat}
So document 2 was counted twice. |
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