[SOLR-7377] SOLR Streaming Expressions

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 5.2, 6.0
• Component/s: clients - java
• Assignee: Unassigned
• Reporter: Dennis Gove
• Created: 10/Apr/15 19:50
• Updated: 08/Oct/19 14:51
• Resolved: 27/May/15 03:13

Description

It would be beneficial to add an expression-based interface to Streaming API described in SOLR-7082. Right now that API requires streaming requests to come in from clients as serialized bytecode of the streaming classes. The suggestion here is to support string expressions which describe the streaming operations the client wishes to perform.

search(collection1, q=*:*, fl="id,fieldA,fieldB", sort="fieldA asc")

With this syntax in mind, one can now express arbitrarily complex stream queries with a single string.

// merge two distinct searches together on common fields
merge(
  search(collection1, q="id:(0 3 4)", fl="id,a_s,a_i,a_f", sort="a_f asc, a_s asc"),
  search(collection2, q="id:(1 2)", fl="id,a_s,a_i,a_f", sort="a_f asc, a_s asc"),
  on="a_f asc, a_s asc")

// find top 20 unique records of a search
top(
  n=20,
  unique(
    search(collection1, q=*:*, fl="id,a_s,a_i,a_f", sort="a_f desc"),
    over="a_f desc"),
  sort="a_f desc")

The syntax would support
1. Configurable expression names (eg. via solrconfig.xml one can map "unique" to a class implementing a Unique stream class) This allows users to build their own streams and use as they wish.
2. Named parameters (of both simple and expression types)
3. Unnamed, type-matched parameters (to support requiring N streams as arguments to another stream)
4. Positional parameters

The main goal here is to make streaming as accessible as possible and define a syntax for running complex queries across large distributed systems.

Issue Links

• is related to: SOLR-7620 Streaming Expressions fails with confusing error in single node installs