Apache Solr Reference Guide Covering Apache Solr 6.0

With this alternative document model, all of the same queries demonstrated above can still be executed, simply
by changing the " from" param to replace the " in_edge" field with the " id" field:
http://localhost:8983/solr/alt_graph/query?fl=id&q={!graph+from=id+to=out_edge+maxDe
pth=1}foo:[*+TO+10]
...
"response":{"numFound":6,"start":0,"docs":[
{ "id":"A" },
{ "id":"B" },
{ "id":"C" },
{ "id":"D" },
{ "id":"G" },
{ "id":"H" } ]
}
Join Query Parser
JoinQParser extends the QParserPlugin. It allows normalizing relationships between documents with a join
operation. This is different from the concept of a join in a relational database because no information is being
truly joined. An appropriate SQL analogy would be an "inner query".
Examples:
Find all products containing the word "ipod", join them against manufacturer docs and return the list of
manufacturers:
{!join from=manu_id_s to=id}ipod
Find all manufacturer docs named "belkin", join them against product docs, and filter the list to only products with
a price less than $12:
q = {!join from=id to=manu_id_s}compName_s:Belkin
fq = price:[* TO 12]
The join operation is done on a term basis, so the "from" and "to" fields must use compatible field types. For
example: joining between a StrField and a TrieIntField will not work, likewise joining between a StrFiel
d and a TextField that uses LowerCaseFilterFactory will only work for values that are already lower
cased in the string field.
Scoring
You can optionally use the score parameter to return scores of the subordinate query. The values to use for this
parameter define the type of aggregation, which are avg (average), max (maximum), min (minimum) total, or
none.
Joining Across Collections
You can also specify a fromIndex parameter to join with a field from another core or collection. If running in
SolrCloud mode, then the collection specified in the fromIndex parameter must have a single shard and a
replica on all Solr nodes where the collection you're joining to has a replica.
Let's consider an example where you want to use a Solr join query to filter movies by directors that have won an
Oscar. Specifically, imagine we have two collections with the following fields:
movies: id, title, director_id, ...
Apache Solr Reference Guide 6.0
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