Jack Krupansky created LUCENE-4376:
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Summary: Add Query subclasses for selecting documents where a
field is empty or not
Key: LUCENE-4376
URL: https://issues.apache.org/jira/browse/LUCENE-4376
Project: Lucene - Core
Issue Type: Bug
Components: core/query/scoring
Reporter: Jack Krupansky
Fix For: 5.0
Users frequently wish to select documents based on whether a specified
sparsely-populated field has a value or not. Lucene should provide specific
Query subclasses that optimize for these two cases, rather than force users to
guess what workaround might be most efficient. It is simplest for users to use
a simple pure wildcard term to check for non-empty fields or a negated pure
wildcard term to check for empty fields, but it has been suggested that this
can be rather inefficient, especially for text fields with many terms.
1. Add NonEmptyFieldQuery - selects all documents that have a value for the
specified field.
2. Add EmptyFieldQuery - selects all documents that do not have a value for the
specified field.
The query parsers could turn a pure wildcard query (asterisk only) into a
NonEmptyFieldQuery, and a negated pure wildcard query into an EmptyFieldQuery.
Alternatively, maybe PrefixQuery could detect pure wildcard and automatically
"rewrite" it into NonEmptyFieldQuery.
My assumption is that if the actual values of the field are not needed, Lucene
can much more efficiently simply detect whether values are present, rather
than, for example, the user having to create a separate boolean "has value"
field that they would query for true or false.
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