luceneIndex

Purpose

Lucene is a full text indexing and searching technology written by Apache. Lucene provides low-level text indexing and searching facilities. This accessor adds a layer over Lucene to support indexing over the content XML documents preserving the xpath locations of the content. This approach allows content to be located down to the element level across multiple documents.

The luceneIndex accessor supports creation and clearing of indexes. Indexes are specified using the <index> element in the operator document. The index location must be an ffcpl: schemed URI that points to a unique directory space. The physical lucene index will occupy this directory and create files within it.

Before documents can be indexed the index must be created. Specifying a <reset/> flag in the operator document will initialise a new index or empty an existing one.

After adding to an index it must be closed and optimised for searching. Using a single luceneIndex instruction with just the index specified in the operator and a <close/> tag.

The index usually indexes the contents of the operand document against the contents xpath within the document. This is useful when indexing well structured documents and search for particular fields. By specifying the <flat/> flag in the operator document all the text of the document is merged and indexed at the root. This results in smaller and more efficient searches over more freeform text based documents.

The URI of indexed documents is stored within the index but in addition it is sometimes useful to store an independent id field. This can be specified with a <id> element within the operator document.