GET /_search
{
"query": {
"bool": {
"must": {
"match": {
"text": "apple"
}
},
"must_not": {
"match": {
"text": "pie tart fruit crumble tree"
}
}
}
}
}Not Quite Not
A search on the Internet for `Apple'' is likely to return results about the
company, the fruit, and various recipes. We could try to narrow it down to
just the company by excluding words like `pie, tart, crumble, and tree,
using a must_not clause in a bool query:
But who is to say that we wouldn’t miss a very relevant document about Apple
the company by excluding tree or crumble? Sometimes, must_not can be
too strict.
boosting Query
The {ref}/query-dsl-boosting-query.html[boosting query] solves this problem.
It allows us to still include results that appear to be about the fruit or
the pastries, but to downgrade them—to rank them lower than they would
otherwise be:
GET /_search
{
"query": {
"boosting": {
"positive": {
"match": {
"text": "apple"
}
},
"negative": {
"match": {
"text": "pie tart fruit crumble tree"
}
},
"negative_boost": 0.5
}
}
}It accepts a positive query and a negative query. Only documents that
match the positive query will be included in the results list, but documents
that also match the negative query will be downgraded by multiplying the
original _score of the document with the negative_boost.
For this to work, the negative_boost must be less than 1.0. In this
example, any documents that contain any of the negative terms will have their
_score cut in half.