ElasticSearch aggregation - buckets/scripted_metric - elasticsearch

Question

i try to calculate rate function rate(val,ts)= v2-v1/t2-t1 for each document in my index.
My mappings are in form : { "name":keyword","value":"double","timestamp":"integer"}.
So for an example if i have 2 documents in my index:
doc1:{"name":name1,"value":5,"timestamp":2 }
doc2: {name":name1,"value":10,"timestamp":3 },
i need to get result(ts=3) = (10-5)/(3-2).
Is there any way to do this in elasticsearch?
I tried to write my own metric script in this form :
GET test1/_search
{
"size":15,
"aggs":{
"sum_the_hard_way": {
"scripted_metric": {
"init_script": {
"source": "state.values = []; state.timestamps = [];"
},
"map_script": {
"source": "state.values.add(doc['value'].value);state.timestamps.add(doc['timestamp'].value);"
},
"combine_script": {
"source": "def rates = []; for ( int i = 0; i <= state.values.size()-1 ; i++ ) { rate[i+1] = (state.value[i+1]- state.value[i])/(state.timestamp[i+1]- state.timestamp[i]);} return values"
},
"reduce_script": {
"source": "def vals = []; for (a in states) { vals.add(a) } return vals"
}
}
}
}
}
But it doesn't work, i got
"reason" : "index_out_of_bounds_exception: Index 0 out of bounds for
length
Thank you in advance!

Answer 1

TLDR;
Some type slipped into your code.
I hope I have fixed it.
GET /so_agg_painless/_search
{
"size":15,
"aggs":{
"sum_the_hard_way": {
"scripted_metric": {
"init_script": {
"source": """
state.values = [];
state.timestamps = [];
"""
},
"map_script": {
"source": """
state.values.add(doc['value'].value);
state.timestamps.add(doc['timestamp'].value);
"""
},
"combine_script": {
"source": """
def rates = [];
for ( int i = 0; i <= state.values.size()-2 ; i++ ) {
def nom = (state.values[i+1]- state.values[i]);
def denom = (state.timestamps[i+1]- state.timestamps[i]);
rates.add(nom/denom);
}
return rates
"""
},
"reduce_script": {
"source": """
def vals = [];
for (a in states) {
vals.add(a)
}
return vals
"""
}
}
}
}
}
Hey man, you have many typos in your code, that's why it is failing.
But I think the logic is perfect so kudos to you, so were super close.
You need to pay attention to those s in your code.
Also as you may see in the code I posted. use the """. So you can indent the code it makes it wayyy easier to read and fix.