Goals

1. User can specify fields in nested object to be indexed. 

2. User can query on these nested fields as well as top level fields. 

Out of Scope

1. Item in collection will not be index and searched.

API

• Add a new method to create a lucene index that takes a callback. The callback gives the user explicit control of how their value is converted to lucene documents and stored in the index. 
  

/**
 * Create a lucene index using default analyzer.
 * @param luceneSerializer A callback which converts a region value to a 
 * Lucene document or documents to be stored in the index.
 */
public void createIndex(String indexName, String regionPath, LuceneSerializer luceneSerializer);

 
 
 
/**
 * An interface for writing the fields of an object into a lucene document
 * The region key will be added as a field to the returned documents.
 */
public interface LuceneSerializer {

  Collection<Document> toDocuments(Object value);
}

• We will provide a built-in implementation for LuceneSerializer. Use fieldnameAtLevel1.fieldnameAtLevel2 to specify a field in the nested object both for indexing and querying. 

For example, the following Customer object contains a Person field. The Person object contains a Page field.

public class Customer implements Serializable {
  private String name;
  private Person contact; // search nested object 
  ......
}
public class Person implements Serializable {
  private String name;
  private String email;
  private int revenue;
  private String address;
  private Page homepage;
  .......
}
public class Page implements Serializable {
  private int id; // search integer in int format
  private String title;
  private String content;
  ......
}

The following example demonstrates how to index nested fields: contact.name, contact.email, contact.address, contact.homepage.title.

Note: each segment is a field name, not a field type, because Customer class could have more than one field of type Person; e.g. Person contact and Person deliveryman. The field name is used to identify the parent field.

// Get LuceneService
LuceneService luceneService = LuceneServiceProvider.get(cache);

// Create Index on fields, some are fields in nested objects:
luceneService.createIndexFactory().setLuceneSerializer(new FlatFormatSeralizer()) /* an out-of-box LuceneSerializer implementation */
      .addField("name").addField("contact.name").addField("contact.email").addField("contact.address").addField("contact.homepage.title")
      .create("customerIndex", "Customer");

// Now to create region
Region CustomerRegion = ((Cache)cache).createRegionFactory(shortcut).create("Customer");

The syntax for querying the nested field is the same as for a top level field, but with the additional qualifying parent field name, such as "contact.name:tzhou11*". This distinguishes which "name" field when there can potentially be more than one 'name' field at different hierarchical levels in the object.

LuceneQuery query = luceneService.createLuceneQueryFactory().create("customerIndex", "Customer", "contact.name:tzhou11*", "name");
 
PageableLuceneQueryResults<K,Object> results = query.findPages();

Out-Of-Box implementation

We'll provide an out-of-box implementation for the LuceneSerializer: FlatFormatSerializer.

It will still create one document for each parent object. But add the nested object as embedded fields of the document. The field name will use the qualified name. 

For example, the FlatFormatSerializer will convert a Customer object into a document as

(name:John11),(contact.name:tzhou11), (contact.email:tzhou11@gmail.com), (contact.address:15220 Wall St), (contact.homepage.id:11), (contact.homepage.title: Mr. tzhou11), (contact.homepage.content: xxx)