Elasticsearch array scoring

I've been stumped on this myself, it really seems like there should be a simple, builtin way to just specify max instead of sum.

Not sure if this is exactly what you're going for, because you lose the match score on any particular item in the array. So you're not getting max of the match score of the best particular item, just a boolean value if anything matches. If it's something more nuanced (say a person's full name, where you want a better match for first and last vs just one or the other) this may not be acceptable because you're throwing out your scores.

If it is acceptable, this workaround seems to work:

{function_score: {  query: {bool: {should: [    {term: {field1: 'foo'}},    {term: {field2: 'foo'}},    {term: {field3: 'foo'}},  ]}},    functions: [    {filter: {term: {field1: 'foo'}}, weight: 1},    {filter: {term: {field2: 'foo'}}, weight: 1},    {filter: {term: {field2: 'foo'}}, weight: 1},  ],  score_mode: 'sum',  boost_mode: 'replace',}}

We need the "query" part to give us the results to further filter, even though we discard the score. This seems like it should really be a filter, but just wrapping this same thing in the filtered query doesn't work. There may be a better option here.

Then, the weight functions just basically give a 1 if there's a match on that field and 0 otherwise. The score_mode tells it to sum those weights, so in your case they all match so we get 3. The boost_mode tells how to combine with the original query, "replace" tells it to ignore the original query score (which has the problem you mentioned that multiple matches in an array are being summed). So, the total score of this query is 3 because there are 3 matches.

It seems more complicated to me, but in my relatively limited testing I haven't noticed performance issues or anything. I'd love to see a better answer if someone more familiar with elasticsearch has one.