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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.search.querytransform;
import com.yahoo.prelude.query.CompositeItem;
import com.yahoo.prelude.query.Item;
import com.yahoo.prelude.query.OrItem;
import com.yahoo.prelude.query.WeakAndItem;
import com.yahoo.processing.request.CompoundName;
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.yql.MinimalQueryInserter;
import com.yahoo.yolean.chain.After;
/**
* Recursively replaces all instances of OrItems with WeakAndItems if the query property weakand.replace is true.
* Otherwise a noop searcher.
*
* @author karowan
*/
@After(MinimalQueryInserter.EXTERNAL_YQL)
public class WeakAndReplacementSearcher extends Searcher {
static final CompoundName WEAKAND_REPLACE = CompoundName.from("weakAnd.replace");
static final CompoundName WAND_HITS = CompoundName.from("wand.hits");
@Override public Result search(Query query, Execution execution) {
if (!query.properties().getBoolean(WEAKAND_REPLACE)) {
return execution.search(query);
}
replaceOrItems(query);
return execution.search(query);
}
/**
* Extracts the queryTree root and the wand.hits property to send to the recursive replacement function
* @param query the search query
*/
private void replaceOrItems(Query query) {
Item root = query.getModel().getQueryTree().getRoot();
int hits = query.properties().getInteger(WAND_HITS, WeakAndItem.defaultN);
query.getModel().getQueryTree().setRoot(replaceOrItems(root, hits));
if (root != query.getModel().getQueryTree().getRoot())
query.trace("Replaced OR by WeakAnd", true, 2);
}
/**
* Recursively iterates over an Item to replace all instances of OrItems with WeakAndItems
* @param item the current item in the replacement iteration
* @param hits the wand.hits property from the request which is assigned to the N value of the new WeakAndItem
* @return the original item or a WeakAndItem replacement of an OrItem
*/
private Item replaceOrItems(Item item, int hits) {
if (!(item instanceof CompositeItem compositeItem)) {
return item;
}
if (compositeItem instanceof OrItem) {
WeakAndItem newItem = new WeakAndItem(hits);
newItem.setWeight(compositeItem.getWeight());
compositeItem.items().forEach(newItem::addItem);
compositeItem = newItem;
}
for (int i = 0; i < compositeItem.getItemCount(); i++) {
Item subItem = compositeItem.getItem(i);
Item replacedItem = replaceOrItems(subItem, hits);
if (replacedItem != subItem) {
compositeItem.setItem(i, replacedItem);
}
}
return compositeItem;
}
}
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