function
package provides tight control over documents scores.
Note: code snippets here should work, but they were never really compiled... so, tests sources under TestCustomScoreQuery, TestFieldScoreQuery and TestOrdValues may also be useful.
Indexing:
f = new Field("score", "7", Field.Store.NO, Field.Index.UN_TOKENIZED); f.setOmitNorms(true); d1.add(f);
Search:
Query q = new FieldScoreQuery("score", FieldScoreQuery.Type.BYTE);Document d1 above would get a score of 7.
Dividing the original score of each document by a square root of its docid (just to demonstrate what it takes to manipulate scores this way)
Query q = queryParser.parse("my query text"); CustomScoreQuery customQ = new CustomScoreQuery(q) { public float customScore(int doc, float subQueryScore, float valSrcScore) { return subQueryScore / Math.sqrt(docid); } };
For more informative debug info on the custom query, also override the name() method:
CustomScoreQuery customQ = new CustomScoreQuery(q) { public float customScore(int doc, float subQueryScore, float valSrcScore) { return subQueryScore / Math.sqrt(docid); } public String name() { return "1/sqrt(docid)"; } };
Taking the square root of the original score and multiplying it by a "short field driven score", ie, the short value that was indexed for the scored doc in a certain field:
Query q = queryParser.parse("my query text"); FieldScoreQuery qf = new FieldScoreQuery("shortScore", FieldScoreQuery.Type.SHORT); CustomScoreQuery customQ = new CustomScoreQuery(q,qf) { public float customScore(int doc, float subQueryScore, float valSrcScore) { return Math.sqrt(subQueryScore) * valSrcScore; } public String name() { return "shortVal*sqrt(score)"; } };