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Pour a Little (Lucene) Sugar in Your Scala


Please say hello to Lucene Sugar: a library that provides a more concise syntax for the Lucene API in the Scala language. Lucene Sugar makes it easier to:

  • compose Lucene indexes using the familiar Scala cake pattern
  • add indexed and/or stored fields to a Lucene document
  • index collections of documents
  • search! (You didn’t really expect that, did you?)

My general goal for Lucene Sugar is to turn some standard operations on their head. For example, instead of:

scala val doc = new Document doc.add(new StringField("string_field", "aString", Store.YES)) doc.add(new LongField("long_field", 123456L, Store.NO)) doc.add(new StoredField("int_field", 10))

you can now write:

scala val doc = new Document doc.addIndexedStoredField("string_field", "aString") doc.addIndexedOnlyField("long_field", 123456L) doc.addStoredOnlyField("int_field", 10)

Lucene Sugar is still in its infancy, but I believe it already offers great value to anyone wishing to use Lucene in Scala code.

Why I Created Sugar

Gilt’s inventory includes millions of different items in limited quantities. These items are sold quickly, which means that our inventory is constantly changing. A few weeks ago I found that I needed a data store capable of:

  • storing items composed of text and numbers
  • being indexed and filtered using extremely specific criteria (for example, all white shirts from Paul Smith that can be shipped to Canada)
  • working quickly and efficiently (a few 100ms per query)
  • being embeddable (I wanted the data management to be self-contained in the service without requiring any external dependencies

I’d used Lucene for other projects, and thought it might be a great fit for what I needed. In fact, it turned out that–despite its wordy API–Lucene works very well. To overcome the excess verbiage issue, I added some “Scala syntactic sugar” around the Lucene API to make it more concise and pleasant to use. After doing some coding, I realized that it could be helpful to convert this higher-level API into a library that could be reused in other projects. (I also badly wanted to publish my first open source Scala project, so this was a very good candidate.)

With Lucene Sugar, we can now build a search and browser service on top of our inventory data; the data is composed of textual attributes such as product name, brand, color and description as well as numeric data like price and size. I hope you find it useful as well!

Photo by Uwe Hermann. Creative Commons license.

Scala 79 lucene 3 gilttech 332 API 7 search 7 lucene sugar 1 libraries 3