Presented at Lucene/Solr Revolution 2014

2. Faceting with Lucene
Block Join Query

3. Agenda
1. Why we need special faceting for
Block Join queries?
2. Proposed Block Join facet component.

4. Introducing myself
Oleg Savrasov, PhD
A programmer
Working for Grid Dynamics
(griddynamics.com)
Work and live in Saint-Petersburg,
Russia

5. Online shopping

6. Jerrica is looking for a dress

7. Huge amount of dresses

8. Facet filters help
Facet
filters
Reduced
amount

9. Tasks to be solved
● Performant Search
● Facet
calculation/filtering
FacetComponent ?

10. Product has many SKU

11. Aggregated facet counts
Facets should
count products,
not SKU.
Expected
facets:
COLOR
Blue : 1
Red : 1
SIZE
S : 1
M : 1

12. Flat documents don’t help
False positive match for
+COLOR:Blue +SIZE:M

13. Separate SKU documents
q = *:*
facet.field = COLOR
facet.field = SIZE
COLOR
Blue : 1
Red : 2
SIZE
S : 2
M : 1
Wrong
numbers!
There is
only one
product

14. Search products only
q = *:*
fq = scope:product
facet.field = COLOR
facet.field = SIZE
COLOR : 0
SIZE : 0
No such
fields in
product
documents

15. Aggregated facet counts
Facets should
count products,
not SKU.
Expected
facets:
COLOR
Blue : 1
Red : 1
SIZE
S : 1
M : 1

16. Solr Block Join Support (since Lucene 3.4.0)
Green
Blue
Yellow
Yellow
Blue
Green
Product
Green
Yellow
Product
Green
Blue
Yellow
Yellow
Product
docId
Child docs Parent doc
Query: {!parent which="scope:product"}COLOR:Blue
1 1 1
Block
1
1 1
scope:product
COLOR:Blue
ToParentQuery 1 1

17. SOLR-5743 Faceting with Block Join support
● Create BlockJoinFacetComponent
● ToParentQuery is expected
● Facet counts should correspond to
amount of parent documents
● Only DocValues fields are
supported

18. Faceting over DocSet slices
Green
Blue
Yellow
Yellow
Blue
Green
Product
Green
Yellow
Product
Green
Blue
Yellow
Yellow
Product
docId
0 1 0 0 1 0 1
DocSet Slice
DocSet Slice counts
COLOR Blue : 2
Aggregated counts
COLOR Blue : +1

19. Block Join Facet Component

20. BlockJoinFacetCollector

21. Facets counting

22. It works!
q =
{!parent which="scope:product"}
COLOR:Blue
child.facet.field = SIZE
<response>
...
<lst name="facet_counts">
<lst name="facet_fields">
<lst name="SIZE">
<int name="S">14</int>
<int name="L">22</int>
<int name="XL">17</int>
</lst>
</lst>
</lst>
</response>

23. The dress is found

24. Further improvements
● Thorough profiling
● Performance improvements
● Algorithmic improvements

25. References
http://www.slideshare.net/MarkHarwood/proposal-for-nested-document-support-in-
lucene
http://blog.mikemccandless.com/2012/01/searching-relational-content-with.html
http://blog.griddynamics.com/2013/09/solr-block-join-support.html

26. Big thanks!
Please vote for SOLR-5743.
Do you have any questions?