1 files changed, 66 insertions, 0 deletions
diff --git a/container-search/src/main/java/com/yahoo/search/querytransform/WeakAndReplacementSearcher.java b/container-search/src/main/java/com/yahoo/search/querytransform/WeakAndReplacementSearcher.java
new file mode 100644
index 00000000000..058f6b93ae3
--- /dev/null
+++ b/container-search/src/main/java/com/yahoo/search/querytransform/WeakAndReplacementSearcher.java
@@ -0,0 +1,66 @@
+package com.yahoo.search.querytransform;
+
+import com.yahoo.prelude.query.*;
+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;
+
+/**
+ * Recursively replaces all instances of OrItems with WeakAndItems if the query property weakand.replace is true.
+ * Otherwise a noop searcher.
+ *
+ * @author karowan
+ */
+public class WeakAndReplacementSearcher extends Searcher {
+    private static final CompoundName WEAKAND_REPLACE = new CompoundName("weakAnd.replace");
+
+    @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)) {
+            return item;
+        }
+        CompositeItem compositeItem = (CompositeItem) 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;
+    }
+}