What is the difference between Lucene and Elasticsearch
I know ElasticSearch is built upon Apache Lucene but I want to know the significant differences between the two.
Lucene is a Java library. You can include it in your project and refer to its functions using function calls.
Elasticsearch is a JSON Based, Distributed, web server built over Lucene. Though it's Lucene who is doing the actual work beneath, Elasticsearch provides us a convenient layer over Lucene. Each shard that gets created in Elasticsearch is a separate Lucene instance. So to summarize
- Elasticsearch is built over Lucene and provides a JSON based REST API to refer to Lucene features.
- Elasticsearch provides a distributed system on top of Lucene. A distributed system is not something Lucene is aware of or built for. Elasticsearch provides this abstraction of distributed structure.
- Elasticsearch provides other supporting features like thread-pool, queues, node/cluster monitoring API, data monitoring API, Cluster management, etc.
In addition to @Vineeth Mohan words:
High Availability: Elasticsearch is distributed, so that it can manage data replication, which means having multiple copies of data in your cluster. This enables high availability.
Powerful Query DSL:Elasticsearch offers us, JSON interface for reading and writing queries on top of Lucene. Thanks to Elasticsearch, you can write complex queries without knowing Lucene syntax.
Schemaless (Schema-Free): Fields(name,value pairs) for schema do not have to be defined before. When you index data, elasticsearch can create schema automatically at runtime, like magic.