Lucene vs Milvus: What are the differences?

Introduction

Lucene and Milvus are both search index libraries that are widely used in applications. However, there are key differences between the two which make them suitable for different use cases.

1. Scalability: Lucene is designed to handle small to medium-sized text indexes, while Milvus is built specifically for large-scale similarity search. Milvus utilizes a scalable index structure that can efficiently handle billions of vectors or high-dimensional data.

2. Data Type: Lucene primarily supports text-based search indexes, focusing on full-text search and analysis. On the other hand, Milvus emphasizes similarity search on vector data. It provides specialized algorithms and features for handling high-dimensional data points.

3. Query Types: Lucene supports a wide range of search operations such as exact match, fuzzy match, phrase match, and range queries. In contrast, Milvus focuses on similarity search and provides various distance metrics to measure the similarity between vectors. It allows for tasks such as nearest neighbor search and similarity ranking.

4. Indexing Mechanism: Lucene utilizes an inverted index mechanism which allows for fast document retrieval based on terms or keywords. Milvus employs an advanced index structure known as the inverted multi-index (IMI), which enables efficient vector similarity search by indexing data points based on their similarity values.

5. Community Support: Lucene has a long-standing and well-established open-source community with a large number of contributors and resources. Milvus is a relatively newer project but is also open-source and actively maintained. However, due to its focus on vector similarity search, the community support and availability of resources may be comparatively smaller.

6. Applications: Lucene is commonly used in applications that require textual analysis, search engines, and information retrieval systems. Milvus is well-suited for applications that involve similarity search, such as recommendation systems, image search, and anomaly detection.

In summary, Lucene is suitable for text-based search and analysis with smaller dataset sizes, while Milvus is designed for efficient similarity search on large-scale vector data or high-dimensional data.