In ElasticSearch, how do I filter the nested documents in my result? - elasticsearch

Question

Suppose, in ElasticSearch 5, I have data with nesting like:
{"number":1234, "names": [
{"firstName": "John", "lastName": "Smith"},
{"firstName": "Al", "lastName": "Jones"}
]},
...
And I want to query for hits with number 1234 but return only the names that match "lastName": "Jones", so that my result omits names that don't match. In other words, I want to get back only part of the matching document, based on a term query or similar.
A simple nested query won't do, as such would be filtering top-level results. Any ideas?
{ "query" : { "bool": { "filter":[
{ "term": { "number":1234} },
???? something with "lastName": "Jones" ????
] } } }
I want back:
hits: [
{"number":1234, "names": [
{"firstName": "Al", "lastName": "Jones"}
]},
...
]

Answer 1

hits section returns a _source - this is exactly the same document you have indexed.
You are right, nested query filters top-level results, but with inner_hits it will show you which inner nested objects caused these top-level documents to be returned, and this is exactly what you need.
names field can be excluded from top-level hits using _source parameter.
{
"_source": {
"excludes": ["names"]
},
"query":{
"bool":{
"must":[
{
"term":{
"number":{
"value":"1234"
}
}
},
{
"nested":{
"path":"names",
"query":{
"term":{
"names.lastName":"Jones"
}
},
"inner_hits":{
}
}
}
]
}
}
}
So now top-level documents are returned without names field, and you have an additional inner_hits section with the names that match.
You should treat nested objects as part of a top-level document.
If you really need them to be separate - consider parent/child relations.

Answer 2

Try something like this
{
"query": {
"filtered": {
"query": {
"match_all": {}
},
"filter": {
"bool": {
"must": [
{
{ "term": { "number":1234} }
},
{
"nested": {
"path": "something",
"query": {
"term": {
"something.lastName": "Jones"
}
},
"inner_hits" : {}
}
}
]
}
}
}
}
}
I used this Refrence

Answer 3

Similar but a bit different, use the should parameter and then look at inner hits for the names. This will return the top level doc and then inner_hits will have any hits.
{
"_source": {
"excludes": ["names"]
},
"query":{
"bool":{
"must":[
{
"term":{
"number":{
"value":"1234"
}
}
}
],
should: [
{
"nested":{
"path":"names",
"query":{
"term":{
"names.lastName":"Jones"
}
},
"inner_hits":{
}
}
}
]
}
}
}