I have been researching how indexes work in different database systems, and I found that most relational databases like MySQL (InnoDB), PostgreSQL, and Oracle use B+Tree for indexing.
However, in the MongoDB documentation, it is mentioned that indexes in MongoDB use B-Tree rather than B+Tree.
My understanding is that B+Tree is generally more efficient for range queries (BETWEEN, ORDER BY) because:
- Data is stored only in leaf nodes, while internal nodes are used for navigation.
- Leaf nodes are linked, making sequential scans faster.
- B+Tree maintains a consistent structure for inserts/updates, reducing fragmentation.
Meanwhile, B-Tree stores data in both internal nodes and leaf nodes, which might lead to:
- Less efficient range queries.
- More complex insert/update operations.
- Possibly worse performance for full table scans.
Given these differences, my question is:
Why does MongoDB use B-Tree instead of B+Tree for indexing?
- Is there a specific reason related to MongoDB’s architecture that makes B-Tree a better fit?
- Does MongoDB implement any optimizations to improve the efficiency of range queries despite using B-Tree?
- Could there be any plans to adopt B+Tree in future versions for better performance?
Any insights from MongoDB engineers or database experts would be greatly appreciated. Thanks in advance!