With database systems, it is fairly common and expected that a mature database will have indexes and constraint implementations. These are crucial for

How Memgraph Uses Skip Lists for Fast Indexes and Unique Constraints

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2024-11-26 12:00:06

With database systems, it is fairly common and expected that a mature database will have indexes and constraint implementations. These are crucial for ensuring the speed of retrieval and data consistency in the database.

The general concepts of the indexes and constraints are quite similar across different database systems, but the specific details on implementation, benefits, and disadvantages are fairly specific to each database system.

This post will walk you through Memgraph’s approach to indexes and constraints, highlighting how skip lists power both these mechanisms and the pros and cons of this design choice.

A skip list is a clever, probabilistic data structure designed for fast search, insertion, and deletion—similar to a B-tree but without the strict balancing rules. Instead, it uses multiple layers of linked lists to achieve efficiency.

At its core, the skip list is a sorted linked list at the bottom layer. Additional layers sit on top, skipping over chunks of elements from the layer below. This "skipping" drastically reduces the number of nodes you need to traverse for most operations.