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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.prelude.querytransform;
import com.yahoo.component.chain.dependencies.After;
import com.yahoo.component.chain.dependencies.Before;
import com.yahoo.prelude.Index;
import com.yahoo.prelude.IndexFacts;
import com.yahoo.prelude.query.CompositeItem;
import com.yahoo.prelude.query.Item;
import com.yahoo.prelude.query.NotItem;
import com.yahoo.prelude.query.RankItem;
import com.yahoo.prelude.query.TermItem;
import com.yahoo.prelude.query.WordItem;
import com.yahoo.search.Query;
import com.yahoo.search.Result;
import com.yahoo.search.Searcher;
import com.yahoo.search.searchchain.Execution;
import com.yahoo.search.searchchain.PhaseNames;
import java.util.Iterator;
import static com.yahoo.prelude.querytransform.StemmingSearcher.STEMMING;
import static com.yahoo.language.LinguisticsCase.toLowerCase;
/**
* Adds rank terms to boost hits matching exact literals fields using info
* from indexing commands.
*
* @author bratseth
*/
@Before(STEMMING)
@After(PhaseNames.UNBLENDED_RESULT)
public class LiteralBoostSearcher extends Searcher {
@Override
public Result search(Query query, Execution execution) {
addRankTerms(query, execution.context().getIndexFacts().newSession(query));
return execution.search(query);
}
private void addRankTerms(Query query, IndexFacts.Session indexFacts) {
RankItem newRankTerms = new RankItem();
addLiterals(newRankTerms, query.getModel().getQueryTree().getRoot(), indexFacts);
if (newRankTerms.getItemCount() > 0)
addTopLevelRankTerms(newRankTerms, query);
if (query.getTrace().getLevel() >= 2 && newRankTerms.getItemCount() > 0)
query.trace("Added rank terms for possible literal field matches.", true, 2);
}
/**
* Adds a RankItem at the root of a query, but only if there is
* at least one rank term in the specified RankItem.
* If the root is already a RankItem, just append the new rank terms.
*
* @param rankTerms the new rank item to add.
* @param query the query to add to
*/
private void addTopLevelRankTerms(RankItem rankTerms, Query query) {
Item root = query.getModel().getQueryTree().getRoot();
if (root instanceof RankItem) {
for (Iterator<Item> i = rankTerms.getItemIterator(); i.hasNext(); ) {
((RankItem)root).addItem(i.next());
}
}
else {
rankTerms.addItem(0, root);
query.getModel().getQueryTree().setRoot(rankTerms);
}
}
private void addLiterals(RankItem rankTerms, Item item, IndexFacts.Session indexFacts) {
if (item instanceof NotItem) {
addLiterals(rankTerms, ((NotItem) item).getPositiveItem(), indexFacts);
}
else if (item instanceof CompositeItem) {
for (Iterator<Item> i = ((CompositeItem)item).getItemIterator(); i.hasNext(); )
addLiterals(rankTerms, i.next(), indexFacts);
}
else if (item instanceof TermItem) {
TermItem termItem = (TermItem)item;
Index index = indexFacts.getIndex(termItem.getIndexName());
if (index.getLiteralBoost())
rankTerms.addItem(new WordItem(toLowerCase(termItem.getRawWord()), index.getName() + "_literal"));
}
}
}
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