Merge pull request #9918 from vespa-engine/balder/collapse-single-child-under-sameElement

A single element under sameElement operator can be pulled out to avoi…

9 files changed, 60 insertions, 11 deletions

diff --git a/container-search/abi-spec.json b/container-search/abi-spec.json
index 8f9dc33e944..cc06710480d 100644
--- a/container-search/abi-spec.json
+++ b/container-search/abi-spec.json
@@ -436,6 +436,7 @@
       "public void lock()",
       "public boolean isLocked()",
       "public int getTermCount()",
+      "public java.util.Optional extractSingleChild()",
       "public bridge synthetic com.yahoo.prelude.query.Item clone()",
       "public bridge synthetic java.lang.Object clone()"
     ],
@@ -854,7 +855,8 @@
       "abstract"
     ],
     "methods": [
-      "public void <init>()"
+      "public void <init>()",
+      "public java.util.Optional extractSingleChild()"
     ],
     "fields": []
   },
@@ -944,6 +946,7 @@
       "public void addItem(com.yahoo.prelude.query.Item)",
       "public void addItem(int, com.yahoo.prelude.query.Item)",
       "public com.yahoo.prelude.query.Item setItem(int, com.yahoo.prelude.query.Item)",
+      "public java.util.Optional extractSingleChild()",
       "public com.yahoo.prelude.query.WordItem getWordItem(int)",
       "public com.yahoo.prelude.query.BlockItem getBlockItem(int)",
       "protected void encodeThis(java.nio.ByteBuffer)",
@@ -974,6 +977,7 @@
       "public void setIndexName(java.lang.String)",
       "public void setWeight(int)",
       "public void addItem(com.yahoo.prelude.query.Item)",
+      "public java.util.Optional extractSingleChild()",
       "public com.yahoo.prelude.query.WordItem getWordItem(int)",
       "protected void encodeThis(java.nio.ByteBuffer)",
       "public int encode(java.nio.ByteBuffer)",
@@ -1239,6 +1243,7 @@
       "protected void appendHeadingString(java.lang.StringBuilder)",
       "protected void appendBodyString(java.lang.StringBuilder)",
       "protected void adding(com.yahoo.prelude.query.Item)",
+      "public java.util.Optional extractSingleChild()",
       "public com.yahoo.prelude.query.Item$ItemType getItemType()",
       "public java.lang.String getName()",
       "public java.lang.String getFieldName()"
diff --git a/container-search/src/main/java/com/yahoo/prelude/query/CompositeItem.java b/container-search/src/main/java/com/yahoo/prelude/query/CompositeItem.java
index 907eabe60ce..64f759dcf9c 100644
--- a/container-search/src/main/java/com/yahoo/prelude/query/CompositeItem.java
+++ b/container-search/src/main/java/com/yahoo/prelude/query/CompositeItem.java
@@ -13,6 +13,7 @@ import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.ListIterator;
+import java.util.Optional;
 
 
 /**
@@ -379,4 +380,13 @@ public abstract class CompositeItem extends Item {
         return terms;
     }
 
+    /**
+     * Will return its single child if itself can safely be omitted.
+     *
+     * @return a valid Item or empty Optional if it can not be done
+     */
+    public Optional<Item> extractSingleChild() {
+        return getItemCount() == 1 ? Optional.of(getItem(0)) : Optional.empty();
+    }
+
 }
diff --git a/container-search/src/main/java/com/yahoo/prelude/query/NonReducibleCompositeItem.java b/container-search/src/main/java/com/yahoo/prelude/query/NonReducibleCompositeItem.java
index 84aa177369a..97d724953ea 100644
--- a/container-search/src/main/java/com/yahoo/prelude/query/NonReducibleCompositeItem.java
+++ b/container-search/src/main/java/com/yahoo/prelude/query/NonReducibleCompositeItem.java
@@ -1,6 +1,8 @@
 // Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.prelude.query;
 
+import java.util.Optional;
+
 /**
  * A composite item which specifies semantics which are not maintained
  * if an instance with a single child is replaced by the single child.
@@ -12,4 +14,8 @@ package com.yahoo.prelude.query;
  * @author bratseth
  */
 public abstract class NonReducibleCompositeItem extends CompositeItem {
+    @Override
+    public Optional<Item> extractSingleChild() {
+        return Optional.empty();
+    }
 }
diff --git a/container-search/src/main/java/com/yahoo/prelude/query/PhraseItem.java b/container-search/src/main/java/com/yahoo/prelude/query/PhraseItem.java
index 26da5eec7eb..4de0af1f408 100644
--- a/container-search/src/main/java/com/yahoo/prelude/query/PhraseItem.java
+++ b/container-search/src/main/java/com/yahoo/prelude/query/PhraseItem.java
@@ -5,6 +5,7 @@ import com.yahoo.prelude.query.textualrepresentation.Discloser;
 
 import java.nio.ByteBuffer;
 import java.util.Iterator;
+import java.util.Optional;
 
 /**
  * A term which contains a phrase - a collection of word terms
@@ -127,6 +128,13 @@ public class PhraseItem extends CompositeIndexedItem {
         }
     }
 
+    @Override
+    public Optional<Item> extractSingleChild() {
+        Optional<Item> extracted = super.extractSingleChild();
+        extracted.ifPresent(e -> e.setWeight(this.getWeight()));
+        return extracted;
+    }
+
     private void addIndexedItem(IndexedItem word) {
         word.setIndexName(this.getIndexName());
         super.addItem((Item) word);
diff --git a/container-search/src/main/java/com/yahoo/prelude/query/PhraseSegmentItem.java b/container-search/src/main/java/com/yahoo/prelude/query/PhraseSegmentItem.java
index a19a6e53963..53a57a968f5 100644
--- a/container-search/src/main/java/com/yahoo/prelude/query/PhraseSegmentItem.java
+++ b/container-search/src/main/java/com/yahoo/prelude/query/PhraseSegmentItem.java
@@ -5,6 +5,7 @@ import com.yahoo.prelude.query.textualrepresentation.Discloser;
 
 import java.nio.ByteBuffer;
 import java.util.Iterator;
+import java.util.Optional;
 
 
 /**
@@ -55,10 +56,12 @@ public class PhraseSegmentItem extends IndexedSegmentItem {
         super(rawWord, current, isFromQuery, stemmed, substring);
     }
 
+    @Override
     public ItemType getItemType() {
         return ItemType.PHRASE;
     }
 
+    @Override
     public String getName() {
         return "SPHRASE";
     }
@@ -87,6 +90,7 @@ public class PhraseSegmentItem extends IndexedSegmentItem {
      *
      * @throws IllegalArgumentException if the given item is not a WordItem or PhraseItem
      */
+    @Override
     public void addItem(Item item) {
         if (item instanceof WordItem) {
             addWordItem((WordItem) item);
@@ -95,6 +99,13 @@ public class PhraseSegmentItem extends IndexedSegmentItem {
         }
     }
 
+    @Override
+    public Optional<Item> extractSingleChild() {
+        Optional<Item> extracted = super.extractSingleChild();
+        extracted.ifPresent(e -> e.setWeight(this.getWeight()));
+        return extracted;
+    }
+
     private void addWordItem(WordItem word) {
         word.setIndexName(this.getIndexName());
         super.addItem(word);
diff --git a/container-search/src/main/java/com/yahoo/prelude/query/QueryCanonicalizer.java b/container-search/src/main/java/com/yahoo/prelude/query/QueryCanonicalizer.java
index 31e69e5b7cd..88bae76b26d 100644
--- a/container-search/src/main/java/com/yahoo/prelude/query/QueryCanonicalizer.java
+++ b/container-search/src/main/java/com/yahoo/prelude/query/QueryCanonicalizer.java
@@ -4,7 +4,10 @@ package com.yahoo.prelude.query;
 import com.yahoo.search.Query;
 import com.yahoo.search.query.QueryTree;
 
-import java.util.*;
+import java.util.HashSet;
+import java.util.ListIterator;
+import java.util.Optional;
+import java.util.Set;
 
 /**
  * Query normalizer and sanity checker.
@@ -82,15 +85,11 @@ public class QueryCanonicalizer {
         if (composite.getItemCount() == 0)
             parentIterator.remove();
 
-        if (composite.getItemCount() == 1 && ! (composite instanceof NonReducibleCompositeItem)) {
-            if (composite instanceof PhraseItem || composite instanceof PhraseSegmentItem)
-                composite.getItem(0).setWeight(composite.getWeight());
-            parentIterator.set(composite.getItem(0));
-        }
+        composite.extractSingleChild().ifPresent(extractedChild -> parentIterator.set(extractedChild));
 
         return CanonicalizationResult.success();
     }
-    
+
     private static void collapseLevels(CompositeItem composite) {
         if (composite instanceof RankItem || composite instanceof NotItem) {
             collapseLevels(composite, composite.getItemIterator()); // collapse the first item only
diff --git a/container-search/src/main/java/com/yahoo/prelude/query/SameElementItem.java b/container-search/src/main/java/com/yahoo/prelude/query/SameElementItem.java
index aa446140da0..d2c19339298 100644
--- a/container-search/src/main/java/com/yahoo/prelude/query/SameElementItem.java
+++ b/container-search/src/main/java/com/yahoo/prelude/query/SameElementItem.java
@@ -6,6 +6,7 @@ import com.yahoo.protect.Validator;
 
 import java.nio.ByteBuffer;
 import java.util.Iterator;
+import java.util.Optional;
 
 /**
  * This represents a query where all terms are required to match in the same element id.
@@ -54,6 +55,16 @@ public class SameElementItem extends NonReducibleCompositeItem {
         Validator.ensureNonEmpty("Struct fieldname", asTerm.getIndexName());
         Validator.ensureNonEmpty("Query term", asTerm.getIndexedString());
     }
+
+    @Override
+    public Optional<Item> extractSingleChild() {
+        if (getItemCount() == 1) {
+            WordItem child = (WordItem) getItem(0);
+            child.setIndexName(getFieldName() + "." + child.getIndexName());
+            return Optional.of(child);
+        }
+        return Optional.empty();
+    }
     
     @Override
     public ItemType getItemType() {
diff --git a/container-search/src/main/java/com/yahoo/prelude/querytransform/QueryRewrite.java b/container-search/src/main/java/com/yahoo/prelude/querytransform/QueryRewrite.java
index 2d941681f2a..84c793a6df1 100644
--- a/container-search/src/main/java/com/yahoo/prelude/querytransform/QueryRewrite.java
+++ b/container-search/src/main/java/com/yahoo/prelude/querytransform/QueryRewrite.java
@@ -6,7 +6,6 @@ import com.yahoo.prelude.query.CompositeItem;
 import com.yahoo.prelude.query.EquivItem;
 import com.yahoo.prelude.query.Item;
 import com.yahoo.prelude.query.NearItem;
-import com.yahoo.prelude.query.NonReducibleCompositeItem;
 import com.yahoo.prelude.query.NotItem;
 import com.yahoo.prelude.query.NullItem;
 import com.yahoo.prelude.query.OrItem;
@@ -215,7 +214,7 @@ public class QueryRewrite {
                 parent.setItem(i, newChild);
             }
         }
-        return ((numChildren == 1) && !(parent instanceof NonReducibleCompositeItem)) ? parent.getItem(0) : item;
+        return parent.extractSingleChild().orElse(item);
     }
 
     private static Item rewriteSddocname(Item item) {
diff --git a/container-search/src/test/java/com/yahoo/search/yql/YqlParserTestCase.java b/container-search/src/test/java/com/yahoo/search/yql/YqlParserTestCase.java
index 70d50b23bed..00a17f963c6 100644
--- a/container-search/src/test/java/com/yahoo/search/yql/YqlParserTestCase.java
+++ b/container-search/src/test/java/com/yahoo/search/yql/YqlParserTestCase.java
@@ -303,7 +303,7 @@ public class YqlParserTestCase {
         assertCanonicalParse("select foo from bar where baz contains sameElement(key contains \"a\", value.f2 = 10);",
                 "baz:{key:a value.f2:10}");
         assertCanonicalParse("select foo from bar where baz contains sameElement(key contains \"a\");",
-                "baz:{key:a}");
+                "baz.key:a");
     }
 
     @Test