I'm working on a project that uses Elasticsearch
to store data and show some complex statistics.
I have an index in that looks like this:
Reservation {
id: number
check_in: Date
check_out: Date
created_at: Date
// other fields...
}
I need to calculate the average days' difference between check_in
and created_at
of my Reservation
s in a specific date range and show the result as a number.
I tried this query
:
{
"script_fields": {
"avgDates": {
"script": {
"lang": "expression",
"source": "doc['created_at'].value - doc['check_in'].value"
}
}
},
"query": {
"bool": {
"must": [
{
"range": {
"created_at": {
"gte": "{{lastMountTimestamp}}",
"lte": "{{currentTimestamp}}"
}
}
}
]
}
},
"size": 0,
"aggs": {
"avgBetweenDates": {
"avg": {
"field": "avgDates"
}
}
}
}
Dates fields are saved in ISO 8601 form (eg: 2020-03-11T14:25:15+00:00), I don't know if this could produce issues.
It catches some hits, So, the query works for sure! but, it always returns null
as the value of the avgBetweenDates
aggregation.
I need a result like this:
"aggregations": {
"avgBetweenDates": {
"value": 3.14159 // Π is just an example!
}
}
Any ideas will help!
Thank you.
Scripted Fields are not stored fields in ES. You can only perform aggregation on the stored fields as scripted fields
are created on the fly.
You can simply move the script logic in the Average Aggregation as shown below. Note that for the sake of understanding, I've created sample mapping, documents, query and its response.
PUT my_date_index
{
"mappings": {
"properties": {
"check_in":{
"type":"date",
"format": "date_time"
},
"check_out":{
"type": "date",
"format": "date_time"
},
"created_at":{
"type": "date",
"format": "date_time"
}
}
}
}
POST my_date_index/_doc/1
{
"check_in": "2019-01-15T00:00:00.000Z",
"check_out": "2019-01-20T00:00:00.000Z",
"created_at": "2019-01-17T00:00:00.000Z"
}
POST my_date_index/_doc/2
{
"check_in": "2019-01-15T00:00:00.000Z",
"check_out": "2019-01-22T00:00:00.000Z",
"created_at": "2019-01-20T00:00:00.000Z"
}
POST my_date_index/_search
{
"size": 0,
"aggs": {
"my_dates_diff": {
"avg": {
"script": """
ZonedDateTime d1 = doc['created_at'].value;
ZonedDateTime d2 = doc['check_in'].value;
long differenceInMillis = ChronoUnit.MILLIS.between(d1, d2);
return Math.abs(differenceInMillis/86400000);
"""
}
}
}
}
Notice, that you wanted difference in number of days. The above logic does that.
{
"took" : 2,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 2,
"relation" : "eq"
},
"max_score" : null,
"hits" : [ ]
},
"aggregations" : {
"my_dates_diff" : {
"value" : 3.5 <---- Average in Number of Days
}
}
}
Hope this helps!