Replace synchronized Stack with Deque in feed and query path.

4 files changed, 43 insertions, 54 deletions

diff --git a/container-search/src/main/java/com/yahoo/prelude/querytransform/RecallSearcher.java b/container-search/src/main/java/com/yahoo/prelude/querytransform/RecallSearcher.java
index f0a18954e40..98a8e5af00d 100644
--- a/container-search/src/main/java/com/yahoo/prelude/querytransform/RecallSearcher.java
+++ b/container-search/src/main/java/com/yahoo/prelude/querytransform/RecallSearcher.java
@@ -3,7 +3,11 @@ package com.yahoo.prelude.querytransform;
 
 import com.yahoo.component.chain.dependencies.After;
 import com.yahoo.component.chain.dependencies.Before;
-import com.yahoo.prelude.query.*;
+import com.yahoo.prelude.query.CompositeItem;
+import com.yahoo.prelude.query.Item;
+import com.yahoo.prelude.query.NullItem;
+import com.yahoo.prelude.query.RankItem;
+import com.yahoo.prelude.query.WordItem;
 import com.yahoo.prelude.query.parser.AnyParser;
 import com.yahoo.search.Query;
 import com.yahoo.search.Result;
@@ -14,10 +18,10 @@ import com.yahoo.search.query.parser.Parsable;
 import com.yahoo.search.query.parser.ParserEnvironment;
 import com.yahoo.search.result.ErrorMessage;
 import com.yahoo.search.searchchain.Execution;
-import com.yahoo.search.searchchain.PhaseNames;
 
+import java.util.ArrayDeque;
+import java.util.Deque;
 import java.util.Iterator;
-import java.util.Stack;
 
 import static com.yahoo.prelude.querytransform.NormalizingSearcher.ACCENT_REMOVAL;
 import static com.yahoo.prelude.querytransform.StemmingSearcher.STEMMING;
@@ -76,15 +80,14 @@ public class RecallSearcher extends Searcher {
      * @return True if a rank item was found.
      */
     private static boolean hasRankItem(Item root) {
-        Stack<Item> stack = new Stack<>();
+        Deque<Item> stack = new ArrayDeque<>();
         stack.push(root);
         while (!stack.isEmpty()) {
             Item item = stack.pop();
             if (item instanceof RankItem) {
                 return true;
             }
-            if (item instanceof CompositeItem) {
-                CompositeItem lst = (CompositeItem)item;
+            if (item instanceof CompositeItem lst) {
                 for (Iterator<Item> it = lst.getItemIterator(); it.hasNext();) {
                     stack.push(it.next());
                 }
@@ -102,20 +105,18 @@ public class RecallSearcher extends Searcher {
      * @return The first node found.
      */
     private static WordItem findOrigWordItem(Item root, String value) {
-        Stack<Item> stack = new Stack<>();
+        Deque<Item> stack = new ArrayDeque<>();
         stack.push(root);
         while (!stack.isEmpty()) {
             Item item = stack.pop();
             if (item.getCreator() == Item.ItemCreator.ORIG &&
-                item instanceof WordItem)
+                    item instanceof WordItem word)
             {
-                WordItem word = (WordItem)item;
                 if (word.getWord().equals(value)) {
                     return word;
                 }
             }
-            if (item instanceof CompositeItem) {
-                CompositeItem lst = (CompositeItem)item;
+            if (item instanceof CompositeItem lst) {
                 for (Iterator<Item> it = lst.getItemIterator(); it.hasNext();) {
                     stack.push(it.next());
                 }
@@ -130,15 +131,14 @@ public class RecallSearcher extends Searcher {
      * @param root The root of the tree to update.
      */
     private static void updateFilterTerms(Item root) {
-        Stack<Item> stack = new Stack<>();
+        Deque<Item> stack = new ArrayDeque<>();
         stack.push(root);
         while (!stack.isEmpty()) {
             Item item = stack.pop();
             if (item.getCreator() == Item.ItemCreator.FILTER) {
                 item.setRanked(false);
             }
-            if (item instanceof CompositeItem) {
-                CompositeItem lst = (CompositeItem)item;
+            if (item instanceof CompositeItem lst) {
                 for (Iterator<Item> it = lst.getItemIterator(); it.hasNext();) {
                     stack.push(it.next());
                 }
diff --git a/container-search/src/main/java/com/yahoo/search/grouping/request/MathResolver.java b/container-search/src/main/java/com/yahoo/search/grouping/request/MathResolver.java
index 98dd2ee3c88..fd3651e6787 100644
--- a/container-search/src/main/java/com/yahoo/search/grouping/request/MathResolver.java
+++ b/container-search/src/main/java/com/yahoo/search/grouping/request/MathResolver.java
@@ -1,9 +1,10 @@
 // Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.search.grouping.request;
 
+import java.util.ArrayDeque;
+import java.util.Deque;
 import java.util.LinkedList;
 import java.util.List;
-import java.util.Stack;
 
 /**
  * This is a helper class for resolving arithmetic operations over {@link GroupingExpression} objects. To resolve an
@@ -25,7 +26,7 @@ public class MathResolver {
         private final int pre;
         private final String image;
 
-        private Type(int pre, String image) {
+        Type(int pre, String image) {
             this.pre = pre;
             this.image = image;
         }
@@ -57,7 +58,7 @@ public class MathResolver {
         if (items.size() == 1) {
             return items.remove(0).exp; // optimize common case
         }
-        Stack<Item> stack = new Stack<>();
+        Deque<Item> stack = new ArrayDeque<>();
         stack.push(items.remove(0));
         while (!items.isEmpty()) {
             Item item = items.remove(0);
@@ -69,30 +70,19 @@ public class MathResolver {
         while (stack.size() > 1) {
             pop(stack);
         }
-        return stack.remove(0).exp;
+        return stack.pop().exp;
     }
 
-    private void pop(Stack<Item> stack) {
+    private void pop(Deque<Item> stack) {
         Item rhs = stack.pop();
         Item lhs = stack.peek();
         switch (rhs.type) {
-        case ADD:
-            lhs.exp = new AddFunction(lhs.exp, rhs.exp);
-            break;
-        case DIV:
-            lhs.exp = new DivFunction(lhs.exp, rhs.exp);
-            break;
-        case MOD:
-            lhs.exp = new ModFunction(lhs.exp, rhs.exp);
-            break;
-        case MUL:
-            lhs.exp = new MulFunction(lhs.exp, rhs.exp);
-            break;
-        case SUB:
-            lhs.exp = new SubFunction(lhs.exp, rhs.exp);
-            break;
-        default:
-            throw new UnsupportedOperationException("Operator " + rhs.type + " not supported.");
+            case ADD -> lhs.exp = new AddFunction(lhs.exp, rhs.exp);
+            case DIV -> lhs.exp = new DivFunction(lhs.exp, rhs.exp);
+            case MOD -> lhs.exp = new ModFunction(lhs.exp, rhs.exp);
+            case MUL -> lhs.exp = new MulFunction(lhs.exp, rhs.exp);
+            case SUB -> lhs.exp = new SubFunction(lhs.exp, rhs.exp);
+            default -> throw new UnsupportedOperationException("Operator " + rhs.type + " not supported.");
         }
     }
 
diff --git a/container-search/src/main/java/com/yahoo/search/grouping/vespa/RequestBuilder.java b/container-search/src/main/java/com/yahoo/search/grouping/vespa/RequestBuilder.java
index e5b45373370..958f343fac5 100644
--- a/container-search/src/main/java/com/yahoo/search/grouping/vespa/RequestBuilder.java
+++ b/container-search/src/main/java/com/yahoo/search/grouping/vespa/RequestBuilder.java
@@ -18,11 +18,13 @@ import com.yahoo.searchlib.aggregation.HitsAggregationResult;
 import com.yahoo.searchlib.expression.ExpressionNode;
 import com.yahoo.searchlib.expression.RangeBucketPreDefFunctionNode;
 
+import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Objects;
 import java.util.OptionalLong;
-import java.util.Stack;
+import java.util.Deque;
 import java.util.TimeZone;
 
 /**
@@ -61,7 +63,7 @@ class RequestBuilder {
      * @return This, to allow chaining.
      */
     public RequestBuilder setRootOperation(GroupingOperation root) {
-        root.getClass(); // throws NullPointerException
+        Objects.requireNonNull(root, "Root must be non-null");
         this.root = root;
         return this;
     }
@@ -125,7 +127,7 @@ class RequestBuilder {
         Grouping grouping = new Grouping();
         grouping.getRoot().setTag(++tag);
         grouping.setForceSinglePass(root.getForceSinglePass() || root.containsHint("singlepass"));
-        Stack<BuildFrame> stack = new Stack<>();
+        Deque<BuildFrame> stack = new ArrayDeque<>();
         stack.push(new BuildFrame(grouping, new BuildState(), root));
         while (!stack.isEmpty()) {
             BuildFrame frame = stack.pop();
@@ -317,11 +319,10 @@ class RequestBuilder {
         result.setTag(++tag);
 
         String label = exp.getLabel();
-        if (result instanceof HitsAggregationResult) {
+        if (result instanceof HitsAggregationResult hits) {
             if (label != null) {
                 throw new UnsupportedOperationException("Can not label expression '" + exp + "'.");
             }
-            HitsAggregationResult hits = (HitsAggregationResult)result;
             if (frame.state.max != null) {
                 transform.putMax(tag, frame.state.max, "hit list");
                 int offset = transform.getOffset(tag);
diff --git a/container-search/src/test/java/com/yahoo/prelude/querytransform/test/RecallSearcherTestCase.java b/container-search/src/test/java/com/yahoo/prelude/querytransform/test/RecallSearcherTestCase.java
index e2d1555701c..a879f142bcc 100755
--- a/container-search/src/test/java/com/yahoo/prelude/querytransform/test/RecallSearcherTestCase.java
+++ b/container-search/src/test/java/com/yahoo/prelude/querytransform/test/RecallSearcherTestCase.java
@@ -1,13 +1,12 @@
 // Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.prelude.querytransform.test;
 
+import java.util.ArrayDeque;
 import java.util.ArrayList;
-import java.util.Arrays;
+import java.util.Deque;
 import java.util.Iterator;
 import java.util.List;
-import java.util.Stack;
 
-import com.yahoo.prelude.IndexFacts;
 import com.yahoo.search.Query;
 import com.yahoo.search.Result;
 import com.yahoo.prelude.query.CompositeItem;
@@ -45,13 +44,13 @@ public class RecallSearcherTestCase {
     @Test
     void testParse() {
         List<String> empty = new ArrayList<>();
-        assertQueryTree("?query=foo", Arrays.asList("foo"), empty);
-        assertQueryTree("?recall=%2bfoo", empty, Arrays.asList("foo"));
-        assertQueryTree("?query=foo&filter=bar&recall=%2bbaz", Arrays.asList("foo", "bar"), Arrays.asList("baz"));
-        assertQueryTree("?query=foo+bar&filter=baz&recall=%2bcox", Arrays.asList("foo", "bar", "baz"), Arrays.asList("cox"));
-        assertQueryTree("?query=foo&filter=bar+baz&recall=%2bcox", Arrays.asList("foo", "bar", "baz"), Arrays.asList("cox"));
-        assertQueryTree("?query=foo&filter=bar&recall=-baz+%2bcox", Arrays.asList("foo", "bar"), Arrays.asList("baz", "cox"));
-        assertQueryTree("?query=foo%20bar&recall=%2bbaz%20-cox", Arrays.asList("foo", "bar"), Arrays.asList("baz", "cox"));
+        assertQueryTree("?query=foo", List.of("foo"), empty);
+        assertQueryTree("?recall=%2bfoo", empty, List.of("foo"));
+        assertQueryTree("?query=foo&filter=bar&recall=%2bbaz", List.of("foo", "bar"), List.of("baz"));
+        assertQueryTree("?query=foo+bar&filter=baz&recall=%2bcox", List.of("foo", "bar", "baz"), List.of("cox"));
+        assertQueryTree("?query=foo&filter=bar+baz&recall=%2bcox", List.of("foo", "bar", "baz"), List.of("cox"));
+        assertQueryTree("?query=foo&filter=bar&recall=-baz+%2bcox", List.of("foo", "bar"), List.of("baz", "cox"));
+        assertQueryTree("?query=foo%20bar&recall=%2bbaz%20-cox", List.of("foo", "bar"), List.of("baz", "cox"));
     }
 
     private static void assertQueryTree(String query, List<String> ranked, List<String> unranked) {
@@ -65,7 +64,7 @@ public class RecallSearcherTestCase {
         List<String> myRanked = new ArrayList<>(ranked);
         List<String> myUnranked = new ArrayList<>(unranked);
 
-        Stack<Item> stack = new Stack<>();
+        Deque<Item> stack = new ArrayDeque<>();
         stack.push(obj.getModel().getQueryTree().getRoot());
         while (!stack.isEmpty()) {
             Item item = stack.pop();
@@ -85,8 +84,7 @@ public class RecallSearcherTestCase {
                     myUnranked.remove(idx);
                 }
             }
-            if (item instanceof CompositeItem) {
-                CompositeItem lst = (CompositeItem)item;
+            if (item instanceof CompositeItem lst) {
                 for (Iterator<?> it = lst.getItemIterator(); it.hasNext();) {
                     stack.push((Item)it.next());
                 }