Specify size for each subquery in Elasticsearch - elasticsearch

Question

I have query that is similar to union operation in SQL. What i need is to specify the size of result set for each index. For example i want to get 10 records from first index and 15 records from second index.
My query:
{
"query": {
"bool": {
"should": [
{
"bool": {
"must": [{
"match_phrase_prefix": {"userName": "ar" }
}]
}
},
{
"bool": {
"must": [{
"match_phrase_prefix": { "groupName": "ar" }
}]
}
}
]
}
}
}
Url to send query:
http://website.com:9200/user_data,group_data/_search
If you have any thoughts i'd be very grateful.
Thank you

Answer 1

I think you can't do that with a simple query.
But can do that with the Top Hits aggregation, which lets you group result sets by certain fields via a bucket aggregator. Your case should look like:
{
"query": {
"bool": {
"should": [
{
"bool": {
"must": [{
"match_phrase_prefix": {"userName": "ar" }
}]
}
},
{
"bool": {
"must": [{
"match_phrase_prefix": { "groupName": "ar" }
}]
}
}
]
}
}, #Your query stills the same
"size": 0, #This will bring back nothing within the field "hits", so you can focus in the "aggregations" field.
"aggs": {
"10_usernames": {
"top_hits": {
"_source": {
"includes": [ "userName" ]
},
"size" : 10
}
},
"15_groupames": {
"top_hits": {
"_source": {
"includes": [ "groupName" ]
},
"size" : 15
}
}
}
}
You'll see your results within the "aggregations" field.
Hope this is helpful! :D

Answer 2

Ok, thanks for help
Eventually i've chosen another approach. I use Multi Search API, which allows you executing several requests at once. My query is:
POST http://website.com:9200/_msearch
{"index": "user_data"}
{"size":10,"query":{"bool":{"must":[{"match_phrase_prefix":{"userName":"##USER_TEXT##"}}]}}}
{"index": "group_data"}
{"size":15,"query":{"bool":{"must":[{"match_phrase_prefix":{"groupName":"##USER_TEXT##"}}]}}}