Merge branch 'master' into next

Author: CaiJimmy

src/main/java/org/rumbledb/items/ItemFactory.java

@@ -357,6 +357,7 @@ public Item createMapItemRemovingKeys(
             Item original,
             List<Item> keysToRemove
     ) {
+        original = rebaseDeepMapOverlay(original);
         return new MapWithRemovedEntryItem(original, keysToRemove);
     }
 
@@ -365,9 +366,32 @@ public Item createMapItemAddingKey(
             Item keyToAdd,
             List<Item> valueToAdd
     ) {
+        original = rebaseDeepMapOverlay(original);
         return new MapWithAdditionalEntryItem(original, keyToAdd, valueToAdd);
     }
 
+    static int getMapOverlayChainLength(Item item) {
+        if (item instanceof MapWithAdditionalEntryItem additionalEntry) {
+            return additionalEntry.getOverlayChainLength();
+        }
+        if (item instanceof MapWithRemovedEntryItem removedEntry) {
+            return removedEntry.getOverlayChainLength();
+        }
+        return 0;
+    }
+
+    private Item rebaseDeepMapOverlay(Item original) {
+        if (getMapOverlayChainLength(original) < MapWithAdditionalEntryItem.MAX_OVERLAY_CHAIN_LENGTH) {
+            return original;
+        }
+        return createMapItem(
+            original.getItemKeys(),
+            original.getSequenceValues(),
+            ExceptionMetadata.EMPTY_METADATA,
+            false
+        );
+    }
+
     public Item createMapItem(
             List<Item> keys,
             List<List<Item>> values,

src/main/java/org/rumbledb/items/MapWithAdditionalEntryItem.java

@@ -38,17 +38,27 @@ public class MapWithAdditionalEntryItem extends AbstractMapItem {
     @Serial
     private static final long serialVersionUID = 1L;
 
+    static final int MAX_OVERLAY_CHAIN_LENGTH = 32;
+
     /**
      * This is an optimization version of maps when there is exactly one key-value pair.
      */
     private final Item original;
     private final Item additionalKey;
     private final List<Item> additionalValue;
+    private final int size;
+    private final int chainLength;
 
     public MapWithAdditionalEntryItem(Item original, Item additionalKey, List<Item> additionalValue) {
         this.original = original;
         this.additionalKey = additionalKey;
         this.additionalValue = additionalValue;
+        this.size = original.getSize() + (original.hasKey(additionalKey) ? 0 : 1);
+        this.chainLength = ItemFactory.getMapOverlayChainLength(original) + 1;
+    }
+
+    int getOverlayChainLength() {
+        return this.chainLength;
     }
 
     @Override
@@ -114,10 +124,7 @@ public List<Item> getItemKeys() {
 
     @Override
     public int getSize() {
-        if (this.original.hasKey(this.additionalKey)) {
-            return this.original.getSize();
-        }
-        return this.original.getSize() + 1;
+        return this.size;
     }
 
     @Override

src/main/java/org/rumbledb/items/MapWithRemovedEntryItem.java

@@ -46,9 +46,11 @@ public class MapWithRemovedEntryItem extends AbstractMapItem {
      */
     private final Item original;
     private final Set<Item> removedKeys;
+    private final int chainLength;
 
     public MapWithRemovedEntryItem(Item original, List<Item> removedKeys) {
         this.original = original;
+        this.chainLength = ItemFactory.getMapOverlayChainLength(original) + 1;
         this.removedKeys = new HashSet<>();
         for (Item key : removedKeys) {
             if (this.original.isObject()) {
@@ -66,6 +68,10 @@ public MapWithRemovedEntryItem(Item original, List<Item> removedKeys) {
         }
     }
 
+    int getOverlayChainLength() {
+        return this.chainLength;
+    }
+
     @Override
     public Item copy(boolean mutable) {
         if (mutable) {