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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.prelude.querytransform;
import java.util.ListIterator;
import com.yahoo.prelude.query.CompositeItem;
import com.yahoo.prelude.query.Item;
import com.yahoo.prelude.query.PhraseItem;
import com.yahoo.search.Query;
import com.yahoo.search.Result;
import com.yahoo.search.Searcher;
import com.yahoo.search.query.QueryTree;
import com.yahoo.search.searchchain.Execution;
/**
* Make single item phrases in query into single word items.
*
* @author Steinar Knutsen
*/
public class CollapsePhraseSearcher extends Searcher {
@Override
public Result search(Query query, Execution execution) {
QueryTree tree = query.getModel().getQueryTree();
Item root = tree.getRoot();
if (root != null) {
Item newRoot = root.clone();
newRoot = simplifyPhrases(newRoot);
// Sets new root instead of transforming the query tree
// to make code nicer if the root is a single term phrase
if (!root.equals(newRoot)) {
tree.setRoot(newRoot);
query.trace("Collapsing single term phrases to single terms",
true, 2);
}
}
return execution.search(query);
}
private Item simplifyPhrases(Item root) {
if (root == null) {
return root;
}
else if (root instanceof PhraseItem) {
return collapsePhrase((PhraseItem)root);
}
else if (root instanceof CompositeItem) {
CompositeItem composite = (CompositeItem)root;
ListIterator<Item> i = composite.getItemIterator();
while (i.hasNext()) {
Item original = i.next();
Item transformed = simplifyPhrases(original);
if (original != transformed)
i.set(transformed);
}
return root;
}
else {
return root;
}
}
private Item collapsePhrase(PhraseItem root) {
if (root.getItemCount() == 1)
return root.getItem(0);
else
return root;
}
}
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