Elasticsearch - Required terms in a Lucene Query

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I am working on a search query against an Elasticsearch search index. Sometimes, I want to require that a term be present. To address this scenario, I've been reading about the "+" boolean operator. However, I'm slightly confused by it.

I do not understand where it fits against the AND (&&) operator and using the phrase operator ("). For example, lets say I had a search index of animals. Imagine I wanted to find foxes. How is

brown +fox different from brown && fox different from "brown" && "fox". In my understanding, these are very similar. I understand how the last two differ. However, for the life of me, I do not understand why I would ever use the "+" operator.

Any help is appreciated.

1
elasticsearchlucene

1 Answers

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for the life of me, I do not understand why I would ever use the "+" operator.

+ : this term must be present

- : this term must not be present

All other terms are optional. For example, this query:

quick brown +fox -news

states that:

  • fox must be present
  • news must not be present
  • quick and brown are optional — their presence increases the relevance

Phrase Query :

Phrase, surrounded by double quotes — 

"quick brown"

 — searches for all the words in the phrase, in the same order

AND and && are both the same operators i.e. both must be present.

I hope it clarifies.

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