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From Theodan <...@theodan.com>
Subject Sorting with custom SortComparator
Date Wed, 25 Apr 2007 23:27:40 GMT

Hello.

I am trying to sort my query results on a String field called "AssetType"
and then on the relevancy score, but I need a particular ordering of the
possible values in "AssetType" (i.e. first "Video", then "Article", etc.).

I have tried doing this with a custom SortComparator that returns Integers
from getComparable(), as follows:

===========================

public class LuceneIndexSearchCommand extends AbstractSearchCommand {
	
	protected boolean execute(SearchContext context) throws Exception {
		
		...
		
		Hits hits = new Hits();
		
		...

		BooleanQuery keywordQuery = new BooleanQuery();

		...

		Query query = queryParser.parse(finalQuery);

		ConstantScoreRangeQuery constantScoreRangeQuery = new
ConstantScoreRangeQuery("assettype", null, null, true, true);

		BooleanQuery booleanQuery = new BooleanQuery();
		booleanQuery.add(query, Occur.MUST);
		booleanQuery.add(constantScoreRangeQuery, Occur.MUST);

		SortField[] sortFields = new SortField[] {
				new SortField("assettype", new AssetTypeSortComparator()),
				SortField.FIELD_SCORE
		};
		hits.recordHits(searcher.search(booleanQuery, new Sort(sortFields)));
		
		...
        
	}

	private static class AssetTypeSortComparator extends SortComparator {
		
		private static final Map ASSET_TYPE_ORDER_MAP = new HashMap();
		private static final Integer DEFAULT_ORDER = new Integer(3);
		
		static {
			ASSET_TYPE_ORDER_MAP.put("Interactive".toLowerCase(), new Integer(0));
			ASSET_TYPE_ORDER_MAP.put("Video".toLowerCase(), new Integer(0));
			ASSET_TYPE_ORDER_MAP.put("EncyclopediaArticles".toLowerCase(), new
Integer(1));
			ASSET_TYPE_ORDER_MAP.put("Image".toLowerCase(), new Integer(2));
		}
		
		protected Comparable getComparable(String termtext) {
			if (ASSET_TYPE_ORDER_MAP.containsKey(termtext.toLowerCase())) {
				return (Integer)ASSET_TYPE_ORDER_MAP.get(termtext.toLowerCase());
			}
			else {
				return DEFAULT_ORDER;
			}
    	}
		
    };
    
}

===========================

but my Hits don't come back sorted.  They seem to be in the same unsorted
order as before I started trying to use the custom SortComparator.

I have debugged through SortComparator and FieldCacheImpl, and the
"cachedValues" array does seem to correctly contain Integer items
corresponding to most of my 80,000+ docs.  The rest of the items in the
array are null, corresponding to those docs that are missing a value for the
"AssetType" field.

Also, FYI, I am using ConstantScoreRangeQuery because the "AssetType" field
is sometimes missing from certain of the docs, and if I don't use
ConstantScoreRangeQuery then I get NullPointerException on
SortComparator.java:37, as has been discussed before on this mailing list.

Any help would be greatly appreciated.

-Theo
-- 
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