TreeNodeDynamicSize impl part 8 - split internal and merge leaf

Also, RightmostInChain throw instead of setting cursor exception
because it does not rely on any reads.

community/index/src/main/java/org/neo4j/index/internal/gbptree/InternalTreeLogic.java

@@ -459,21 +459,10 @@ private void splitInternal( PageCursor cursor, StructurePropagation<KEY> structu
         // Find position to insert new key
         int pos = positionOf( search( cursor, INTERNAL, newKey, readKey, keyCount ) );
 
-        int keyCountAfterInsert = keyCount + 1;
-        int middlePos = middle( keyCountAfterInsert );
-
         // Update structurePropagation
         structurePropagation.hasRightKeyInsert = true;
         structurePropagation.midChild = current;
         structurePropagation.rightChild = newRight;
-        if ( middlePos == pos )
-        {
-            layout.copyKey( newKey, structurePropagation.rightKey );
-        }
-        else
-        {
-            bTreeNode.keyAt( cursor, structurePropagation.rightKey, pos < middlePos ? middlePos - 1 : middlePos, INTERNAL );
-        }
 
         try ( PageCursor rightCursor = cursor.openLinkedCursor( newRight ) )
         {
@@ -482,11 +471,10 @@ private void splitInternal( PageCursor cursor, StructurePropagation<KEY> structu
             bTreeNode.initializeInternal( rightCursor, stableGeneration, unstableGeneration );
             TreeNode.setRightSibling( rightCursor, oldRight, stableGeneration, unstableGeneration );
             TreeNode.setLeftSibling( rightCursor, current, stableGeneration, unstableGeneration );
-            int rightKeyCount = keyCountAfterInsert - middlePos - 1; // -1 because don't keep prim key in internal
 
             // Do split
-            bTreeNode.doSplitInternal( cursor, keyCount, rightCursor, rightKeyCount, pos, newKey, newRightChild, middlePos, stableGeneration,
-                    unstableGeneration );
+            bTreeNode.doSplitInternal( cursor, keyCount, rightCursor, pos, newKey, newRightChild, stableGeneration, unstableGeneration,
+                    structurePropagation );
         }
 
         // Update old right with new left sibling (newRight)
@@ -1068,7 +1056,7 @@ else if ( TreeNode.isNode( rightSibling ) )
                 rightSiblingCursor.next();
                 int rightSiblingKeyCount = TreeNode.keyCount( rightSiblingCursor );
 
-                if ( bTreeNode.canMergeLeaves( keyCount, rightSiblingKeyCount ) )
+                if ( bTreeNode.canMergeLeaves( cursor, keyCount, rightSiblingCursor, rightSiblingKeyCount ) )
                 {
                     createSuccessorIfNeeded( rightSiblingCursor, structurePropagation, UPDATE_RIGHT_CHILD,
                             stableGeneration, unstableGeneration );

community/index/src/main/java/org/neo4j/index/internal/gbptree/RightmostInChain.java

@@ -68,8 +68,9 @@ void assertNext( PageCursor cursor, long newRightmostNodeGeneration,
         String errorMessage = errorMessageBuilder.toString();
         if ( !errorMessage.equals( "" ) )
         {
-            setPatternException( cursor, newRightmostNodeGeneration, newRightmostLeftSiblingPointer,
+            errorMessage = addPatternToExceptionMessage( newRightmostNodeGeneration, newRightmostLeftSiblingPointer,
                     newRightmostLeftSiblingPointerGeneration, newRightmostNode, errorMessage );
+            throw new IllegalStateException( errorMessage );
         }
 
         // Update currentRightmostNode = newRightmostNode;
@@ -79,16 +80,16 @@ void assertNext( PageCursor cursor, long newRightmostNodeGeneration,
         currentRightmostRightSiblingPointerGeneration = newRightmostRightSiblingPointerGeneration;
     }
 
-    private void setPatternException( PageCursor cursor, long newRightmostGeneration, long leftSibling,
+    private String addPatternToExceptionMessage( long newRightmostGeneration, long leftSibling,
             long leftSiblingGeneration, long newRightmost, String errorMessage )
     {
-        cursor.setCursorException( format( "%s" +
+        return format( "%s" +
                         "  Left siblings view:  %s%n" +
                         "  Right siblings view: %s%n", errorMessage,
                 leftPattern( currentRightmostNode, currentRightmostNodeGeneration,
                         currentRightmostRightSiblingPointerGeneration,
                         currentRightmostRightSiblingPointer ),
-                rightPattern( newRightmost, newRightmostGeneration, leftSiblingGeneration, leftSibling ) ) );
+                rightPattern( newRightmost, newRightmostGeneration, leftSiblingGeneration, leftSibling ) );
     }
 
     private String leftPattern( long actualLeftSibling, long actualLeftSiblingGeneration,

community/index/src/main/java/org/neo4j/index/internal/gbptree/TreeNode.java

@@ -342,7 +342,7 @@ static void goTo( PageCursor cursor, String messageOnError, long nodeId )
      */
     abstract int canRebalanceLeaves( PageCursor leftCursor, int leftKeyCount, PageCursor rightCursor, int rightKeyCount );
 
-    abstract boolean canMergeLeaves( int leftKeyCount, int rightKeyCount );
+    abstract boolean canMergeLeaves( PageCursor leftCursor, int leftKeyCount, PageCursor rightCursor, int rightKeyCount );
 
     /**
      * Calculate where split should be done and move entries between leaves participating in split.
@@ -361,9 +361,9 @@ abstract void doSplitLeaf( PageCursor leftCursor, int leftKeyCount, PageCursor r
      *
      * Key count is updated.
      */
-    abstract void doSplitInternal( PageCursor leftCursor, int leftKeyCount, PageCursor rightCursor, int rightKeyCount, int insertPos,
+    abstract void doSplitInternal( PageCursor leftCursor, int leftKeyCount, PageCursor rightCursor, int insertPos,
             KEY newKey,
-            long newRightChild, int middlePos, long stableGeneration, long unstableGeneration );
+            long newRightChild, long stableGeneration, long unstableGeneration, StructurePropagation<KEY> structurePropagation );
 
     /**
      * Move all rightmost keys and values in left leaf from given position to right node.