ElasticSearch | Randomize results with same score - elasticsearch

Question

In ElasticSearch is it possible to randomize the order of search results with equal score without losing pagination?
I'm hosting a database with thousands of job candidates. When a company are searching for a particular skill (or a combination of skills), it's always the same order (and thus the candidates in the top of search results are having a huge advantage)
Example for a search query:
let params = {
index: 'candidates',
type: 'candidate',
explain: true,
size: size,
from: from,
body: {
_source: {
includes: ['firstName', 'middleName', 'lastName']
},
query: {
bool: {
must: [/* Left out */],
should: [/* Left out */],
}
}
}
};

Answer 1

Henry's answer is good, but I think it is easier to do:
function_score: {
query: {
...
},
random_score: {
seed: 12345678910,
field: '_seq_no',
weight: 0.0001
},
boost_mode: 'sum'
So there is no need to boost the original score, just weight the random score down so that it contributes little (but still enough to break ties).
I do dislike such approach to break ties though, because even if you are contributing just a little to the score, you could still change order of results between results which do not have the same score, but have the score very close. This is why I opened this feature request.

Answer 2

You could use a function_score query, wrap your bool query in it and add a random_score function. Next step is to find the good weighting that match your needs using "boost" and "boost_mode" or "weight"...
Note that if you use filters the output score will be 0 so you will need to change the "boost_mode" from "multiply" to "replace", "sum" or something else...
Finally, don't forget to add a seed (and field as of ES 7.0) to the random_score to keep a near-consistent pagination
From your example I would suggest something like :
let params = {
...
body: {
...
function_score: {
query: {
bool: {
must: [/* Left out */],
should: [/* Left out */],
boost: 100
}
},
random_score: {
seed: 12345678910,
field: '_seq_no'
},
boost_mode: 'sum'
}
}
};