[SOLR-7584] Add Joins to the Streaming API and Streaming Expressions

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Implemented
• Fix Version/s: 6.0
• Component/s: SolrJ
• Labels: Streaming
• Assignee: Dennis Gove
• Reporter: Dennis Gove
• Created: 22/May/15 00:03
• Updated: 09/May/16 18:57
• Resolved: 11/Nov/15 01:48

Description

Add InnerJoinStream, LeftOuterJoinStream, and supporting classes to the Streaming API to allow for joining between sub-streams.

At its basic, it would look something like this

innerJoin(
  search(collection1, q=*:*, fl="fieldA, fieldB, fieldC", ...),
  search(collection2, q=*:*, fl="fieldA, fieldD, fieldE", ...),
  on="fieldA=fieldA"
)

or with multi-field on clauses

innerJoin(
  search(collection1, q=*:*, fl="fieldA, fieldB, fieldC", ...),
  search(collection2, q=*:*, fl="fieldA, fieldD, fieldE", ...),
  on="fieldA=fieldA, fieldB=fieldD"
)

I'd also like to support the option of doing a hash join instead of the default merge join but I haven't yet figured out the best way to express that. I'd like to let the user tell us which sub-stream should be hashed (the least-cost one).

Also, I've been thinking about field aliasing and might want to add a SelectStream which serves the purpose of allowing us to limit the fields coming out and rename fields.

Depends on SOLR-7554

Issue Links

• is related to: SOLR-8125 Umbrella ticket for Streaming and SQL issues