how to sort bucket key to integer in elasticsearch? - elasticsearch

Question

i have a problem with sorting by bucket key.
how do i sort bucket key by integer?
this is my query.
{
"aggregations": {
"by_time": {
"terms": {
"script": {
"source": "Instant.ofEpochMilli(doc['statdate'].date.millis).atZone(ZoneId.of(params.tz)).hour",
"lang": "painless",
"params": {
"tz": "Asia/Seoul"
}
},
"size": 10,
"min_doc_count": 0,
"shard_min_doc_count": 0,
"show_term_doc_count_error": false,
"order": {
"_key": "asc"
}
}
}
}
and result.
{
"aggregations": {
"sterms#by_time": {
"buckets": [
{
"key": "11",
"doc_count": 1
},
{
"key": "19",
"doc_count": 1
},
{
"key": "22",
"doc_count": 1
}
},
{
"key": "7",
"doc_count": 1
},
{
"key": "9",
"doc_count": 7
}
]
}
}
but i don't want this result.
i think what this key type is string.
how can i sort by integer key?

Answer 1

You need to use bucket sort aggregation that is a parent pipeline
aggregation which sorts the buckets of its parent multi-bucket
aggregation. Zero or more sort fields may be specified together with
the corresponding sort order. Each bucket may be sorted based on its
_key, _count or its sub-aggregations.
Try out this search query:
{
"aggregations": {
"by_time": {
"terms": {
"script": {
"source": "Instant.ofEpochMilli(doc['statdate'].date.millis).atZone(ZoneId.of(params.tz)).hour",
"lang": "painless",
"params": {
"tz": "Asia/Seoul"
}
},
"size": 20, <-- note this
"min_doc_count": 0,
"shard_min_doc_count": 0,
"show_term_doc_count_error": false,
"order": {
"_key": "asc"
}
},
"aggs": {
"bucket_truncate": {
"bucket_sort": { <-- note this
"sort": [
{
"_key": {
"order": "asc"
}
}
],
"size": 20 <-- note this
}
}
}
}
}
}
Adding a working example with index data, search query, and search result
Index Data:
{
"id":"1",
"title":"a"
}
{
"id":"3",
"title":"c"
}
{
"id":"2",
"title":"b"
}
{
"id":"2",
"title":"c"
}
Search Query:
{
"size": 0,
"aggs": {
"unique_id": {
"terms": {
"field": "id.keyword"
},
"aggs": {
"bucket_truncate": {
"bucket_sort": {
"sort": [
{
"_key": {
"order": "asc"
}
}
]
}
}
}
}
}
}
Search Result:
"aggregations": {
"unique_id": {
"doc_count_error_upper_bound": 0,
"sum_other_doc_count": 0,
"buckets": [
{
"key": "1",
"doc_count": 1
},
{
"key": "2",
"doc_count": 2
},
{
"key": "3",
"doc_count": 1
}
]
}
}