Field Priority on full text search - elasticsearch

Question

I have a situation in which my products are described in a few and the following structure is used:
{
"defaultDescription" : "Default Description",
"i18nDescription" : {
"pt" : "Descrição Padrão",
"de" : "Standard-Beschreibung"
}
}
Now I have the following requirement: perform a search following a list of prioritized languages (3 languages). If the first language isn't in the i18nDescription, use just the second language, if the second language isn't there use just the third one otherwise match against defaultDescription.
My solution would be something like:
// suppose request comes with the following languages: en, de, pt
{
"size":10,
"fields" : ["defaultDescription", "i18nDescription.en^50", "i18nDescription.de^20", "i18nDescription.pt^10"],
"query": {
"multi_match" : { "query" : "default", "fields" : ["description","descriptions.fr-CA"] }
}
}
But this solution will just sort the result by priority language, I would like to do something like: i18nDescription.en:search OR (i18nDescription.de:search AND _empty_:i18nDescription.en) OR (i18nDescription.pt:search AND _empty_:i18nDescription.en AND _empty_:i18nDescription.de) OR (description:search AND _empty_:i18nDescription.pt AND _empty_:i18nDescription.en AND _empty_:i18nDescription.de)
Is there a way to represent this is a ElasticSearch query?

Answer 1

Playing a bit with bool queries we could reach the desired effect.
It basically needs to check if one field has the text and others (that are more important) are empty, so it would consider just the most important present field.
Query would be something similar to:
{
"size":10,
"query": {
"bool" : {
"should" : [
{
"bool" : {
"must" : [
{ "multi_match" : { "fields":["defaultDescription"], "query" : "default" } },
{ "query_string" : { "query" : "+_missing_:i18nDescription.en +_missing_:i18nDescription.de +_missing_:i18nDescription.pt" } }
]
}
},
{
"bool" : {
"must" : [
{ "multi_match" : { "fields":["i18nDescription.pt"], "query" : "default" } },
{ "query_string" : { "query" : "+_missing_:i18nDescription.en +_missing_:i18nDescription.de" } }
]
}
},
{
"bool" : {
"must" : [
{ "multi_match" : { "fields":["i18nDescription.de"], "query" : "default" } },
{ "query_string" : { "query" : "+_missing_:i18nDescription.en" } }
]
}
},
{
"bool" : {
"must" : [
{ "multi_match" : { "fields":["i18nDescription.en"], "query" : "default" } }
]
}
}
]
}
}
}