Here’s an overview of some of the new features in Solr 6.4.

Download Solr 6.4 to try these features out and give us feedback!
You can also check out upcoming features of the next Solr release.

filter list for facet domain

Any JSON facet command (terms, range, query) can now filter the facet domain in a simpler manner, without resorting to nested query facets.

Example:

json.facet = {
  categories : {
    type : terms, 
    field : cat, 
    domain : { filter:"user:yonik" }
  } 
}

The filters are applied after other domain change operations and are particularly useful when faceting on child documents.
The filter attribute can be a single query or a list of multiple queries to intersect.

Using a param to refer to a filter by query parameter was added shortly after.

Learning to Rank

Learning to Rank (LTR) plugin for reranking results with machine learning models.

See the Lucene/Solr Revolution presentation Learning to Rank in Solr as well
as the Solr Ref Guide.

snapshotcli.sh command line tool to manage snapshots

The full path of the script is ./solr/server/scripts/cloud-scripts/snapshotscli.sh

An example from the pull request:

// Start solr and initialize a sample collection
bin/solr start -c
bin/solr create_collection -c books
curl 'http://localhost:8983/solr/books/update?commit=true' -H 'Content-type:application/json' -d '
[ {"id" : "book1", "title" : "American Gods", "author" : "Neil Gaiman" } ]'

//Create and export a snapshot
./snapshotscli.sh --create snap-1 -c books -z localhost:9983
./snapshotscli.sh --list -c books -z localhost:9983
./snapshotscli.sh --describe snap-1 -c books -z localhost:9983
./snapshotscli.sh --export snap-1 -c books -z localhost:9983 -d /tmp
./snapshotscli.sh --delete snap-1 -c books -z localhost:9983

// Restore the backup and verify the doc count
curl 'http://localhost:8983/solr/admin/collections?action=restore&name=snap-1&location=/tmp&collection=books_restored'
curl 'http://localhost:8983/solr/books_restored/select?q=*:*'

More efficient filter queries

When parsing filter queries (including fq parameters) the standard solr query parser will avoid using BooleanQuery for term disjunctions on string and numeric fields, and will use TermsQuery instead.

This has a number of positive effects:

• Avoids Lucene’s dreaded static maxBooleanClauses issue that causes “too many boolean clauses” exceptions
• The resulting query should be smaller to cache
• The resulting query should have higher performance

For example, the following filter will now be faster, and will no longer throw a “too many boolean clauses” exception:

fq=id:(myid1 myid2 myid3 myid4 ... myid2000)

having streaming expression

The having streaming expression provides functionality like the SQL HAVING clause, and will be used to implement that in the future. Aggregated buckets produced by rollup are filtered by a having clause.

The following streaming expression filters out buckets (authors) with less than 100,000 in sales across all of their books:

having(rollup(over=author,
              sum(sales),
              search(book_sales_collection,
                     q=*:*,
                     fl="author,sales",
                     sort="author asc")),
       gte(sum(sales), 100000))

Also see the a streaming expressions documentation in the ref guide.