CODEWITHSUNDEEP
elasticsearchsolr
Artem Oboturov
Artem Oboturov

Reputation: 4385

Why SOLR has a schema and ElasticSearch does not?

We were comparing those search solutions and started to wonder why one does need a schema and the other does not. What are tradeoffs? Is it because one is like SQL and the other is like NoSQL in sense of schema configuration?

Upvotes: 2

Views: 199

Answers (2)

Alexandre Rafalovitch
Alexandre Rafalovitch

Reputation: 9789

Elasticsearch definitely has a schema. If you think it does not, try indexing a date into a field and then an int into the same field. Or even into different types with the same name (I think ES 2.0 disallows that now).

What Elasticsearch does is simplifies auto-creation of a schema. That has tradeoffs such as possible incorrect type detection, fields that are single-valued or multivalued in the result output based on number of elements they contain (they are always multivalued under the covers), and so on. Elasticsearch has some ways to work around that, mostly by defining some of the schema elements and explicit schema mapping as Oleksii wrote.

Solr also has schemaless mode that closely matches Elasticsearch mode, down to storing all JSON as a single field. And when you enable it, you get both similar benefits and similar disadvantages Elasticsearch has. Except, in Solr, you can change things like order of auto-type strategies and mapping to field types. In Elasticsearch (1.x at least) it was hard coded. You can see - slightly dated - comparison in my presentation from 2014.

As Slomo said, they both use Lucene underneath for storing and most of the search. So, the core engine approach cannot change.

Upvotes: 2

oleksii
oleksii

Reputation: 35925

ES does have a schema defined as templates and mappings. You don't have to use it, but in practice you will. Schema is actually a good thing, and if you notice a database claiming to be pure schemaless - there will be performance implication.

Schema is a tradeoff between ease of developing and adoption against performance. It is easy to read/write into a schemaless database, but it it will be less performant, particularly for any non-trivial query.

Upvotes: 2

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