Elasticsearch query and aggregation on indices - elasticsearch

Question

I have multiple elasticsearch indices and I would like to get the doc_count of how many documents matched the query for each index (even if no documents matched for an index). I tried this (using elasticsearch.js):
{
index: 'one,or,many,indices,here',
query: {
query_string: {
query: 'hello',
},
},
aggs: {
group_by_index: {
terms: {
field: '_index',
min_doc_count: 0,
},
},
},
from: 0,
size: 20,
};
This only works if I specify all indices on the index key. However, I don't always want to match documents across all indices in my search hits.
So I came up with:
{
index: 'all,indices,here',
query: {
bool: {
must: [
{
query_string: {
query: 'hello',
},
},
{
terms: {
_index: 'only,search,hits,indices,here',
},
},
],
},
},
aggs: {
group_by_index: {
terms: {
field: '_index',
min_doc_count: 0,
},
},
},
from: 0,
size: 20,
};
But then I get doc_count: 0 for indices where there are matches because the index is not in the bool query.
How can I get the doc_count for all indices but not get search hits from unwanted indices?

Answer 1

You need to move your index constraint to post_filter
{
index: 'all,indices,here',
query: {
bool: {
must: [
{
query_string: {
query: 'hello',
},
},
],
},
},
aggs: {
group_by_index: {
terms: {
field: '_index',
min_doc_count: 0,
},
},
},
post_filter: {
terms: {
_index: 'only,search,hits,indices,here',
},
},
from: 0,
size: 20,
};