Hello,

I am aggregating tick data and I seem to not understand why I am having issues with summing the volume field. It will not write data until I change **fn: sum** to **fn: last**, however I want to sum the data for this field. Below I attached some sample code with the sum aggregation that does not work as well as the another aggregation for the opening tick data which works just fine. What am I doing wrong?

```
parameters = {
start: -3m,
every: 1m,
limit: 3,
bucket: "CryptoData",
org: "test",
}
dataset = from(bucket: parameters.bucket)
|> range(start: parameters.start)
|> filter(fn: (r) =>
(r["_measurement"] == "CoinbasePro"))
|> filter(fn: (r) =>
(r["_field"] == "volume" or r["_field"] == "price"))
dataset
|> filter(fn: (r) =>
(r["_field"] == "volume"))
|> aggregateWindow(every: parameters.every, fn: sum)
|> map(fn: (r) =>
({
_time: r._time,
product_id: r.product_id,
_field: "volume",
_measurement: r._measurement,
_value: r._value,
topic: r.topic,
symbol: r.symbol,
}))
|> limit(n: parameters.limit)
|> to(bucket: "ohlc_1m_data", org: "none")
dataset
|> filter(fn: (r) =>
(r["_field"] == "price"))
|> aggregateWindow(every: parameters.every, fn: first)
|> map(fn: (r) =>
({
_time: r._time,
product_id: r.product_id,
_field: "open",
_measurement: r._measurement,
_value: r._value,
topic: r.topic,
symbol: r.symbol,
}))
|> limit(n: parameters.limit)
|> to(bucket: "ohlc_1m_data", org: "none")
```