Developer forum

Not on the query. You can extend the index builder to add a field at index time and then query that, but requires a bit of coding.
You can run a schedule with a SQL that adds the information to a 3rd custom product field and have that field indexed...

I see.

Is this a feature worth looking into?

Thank you,
Adrian

I am not sure it is possible because of the way Lucene works.

Here is the words of my friend:

In Lucene (and Lucene.NET), you cannot directly compare the values of two fields within the query syntax. Lucene’s query parser and search execution are designed around field–value comparisons against a constant (like fieldX:123) or a range (fieldX:[100 TO 200]), not field-to-field comparisons.

Why this limitation exists

• Lucene’s core data model is inverted index–based. Queries operate on terms mapped to documents, not row-style expressions where one column can be compared to another.

• At query time, Lucene doesn’t natively join or compare across multiple fields in a single document.

Workarounds

If you need to compare field values, you have a few approaches:

1. Index-time denormalization
   Precompute a comparison field. For example, when indexing, you could store fieldA - fieldB or a flag like fieldA_equals_fieldB. Then you query that derived field.

2. Function queries / FunctionScoreQuery
   In Lucene 4.x (and Lucene.NET 4.8, which tracks that version), you can use ValueSource-based queries (like FunctionQuery or FunctionScoreQuery).
   Example:

   var source = new org.apache.lucene.queries.function.valuesource.DualFloatFunction(
       new IntFieldSource("fieldA"), 
       new IntFieldSource("fieldB"), 
       (a, b) => a - b
   );
   var functionQuery = new FunctionQuery(source);
   

   You can then filter on this (e.g., only docs where fieldA == fieldB or fieldA > fieldB), but it’s more like a scoring hack. Filtering requires wrapping with Filter logic.

3. Post-processing
   Run a broader Lucene query (say, match all documents with constraints on one field) and then in your application code filter the results where fieldA == fieldB.

4. Use an external system (like SQL or Elasticsearch)
   If your use case often requires field-to-field comparisons, Lucene may not be the right tool. Elasticsearch (built on Lucene) supports limited field-to-field scripts using painless scripting.

✅ Short answer: No, Lucene.NET 4.x does not support fieldA:fieldB style queries out of the box. You’ll need to either:

• denormalize at index time,

• use FunctionQuery/ValueSource for custom comparison, or

• filter in application logic after retrieval.