What does `|>` mean in TICKscript - influxdb

Question

Trying to write my fist TICKscript to work out when two sensor values cross: if the outside temperature has changed from lower to higher than the inside temperature then I need to close the windows (and conversely).
Using the query builder in InfluxDB I'm getting this for the meadian of the temperature values inside the house over the last 15 minutes:
from(bucket: "zigbee")
|> range(start: -15m, stop: now())
|> filter(fn: (r) => r["room"] == "Kitchen" or r["room"] == "DiningRoom" or r["room"] == "Bed3" or r["room"] == "Bed1")
|> filter(fn: (r) => r["_field"] == "temperature")
|> group(columns: ["_measurement"])
|> aggregateWindow(every: 15m, fn: mean, createEmpty: false)
|> yield(name:"inside")
The syntax |> appears to undocumented -- can you provide a reference?
Replacing |> with | breaks it.
It seems that group and aggregateWindow do not commute?
Presumably because aggregateWindow is forced to choose a single representative _time value for each window?
I think the plan is to
assign this to a stream,
copy and edit to creata a second stream shifted by 15 minutes,
create a second pair of streams for the outside temperature.
join all four streams and caluclate a value indicating whether the inside and outside temperatures have crossed over.
Unless you have a better idea?
(Right now it's looking easier to import the data into SQL.)

Answer 1

Check InfluxDB Flux language documentation for |>:
InfluxDB Pipe-forward operator
According to your flux syntax query:
from(bucket: "zigbee")
|> range(start: -15m, stop: now())
|> filter(fn: (r) => r["room"] == "Kitchen" or r["room"] == "DiningRoom" or r["room"] == "Bed3" or r["room"] == "Bed1")
|> filter(fn: (r) => r["_field"] == "temperature")
|> group(columns: ["_measurement"])
|> aggregateWindow(every: 15m, fn: mean, createEmpty: false)
|> yield(name:"inside")
You are taking data from bucket "zigbee"
Data from source are passed to range filter function with pipe-forward |> operator
Results from range filter data are passed to next filter function with another pipe-forward operator
Etc.
So all data flows as a result from one function to another.
You can group by but in your case columns are "room" key values if I understand your intentions correctly, so try:
|> group(columns: ["room"])
There is a difference between key values and measurement names - you should check InfluxDB documentation for understatnding data structure.
Flux data model documentation

Answer 2

I'ts not TICKscript, it's something do to with InfluxDB that might be called flux.
mean = from(bucket: "zigbee")
|> range(start: -5d, stop: now())
|> filter(fn: (r) => r["room"] == "Outside")
|> filter(fn: (r) => r["_measurement"] == "temperature")
|> aggregateWindow(every: 30m, fn: mean, createEmpty: false)
shift = mean
|> timeShift(duration: -3h)
j = join(tables: {mean: mean, shift: shift}, on: ["_time"])
|> map(fn: (r) => ({ r with diff: float(v: r._value_mean) - float( v: r._value_shift) }))
// yield contains 1 table with the required columns, but the UI doesn't understand it.
// The UI requires 1 table for each series.
j |> map(fn: (r) => ({_time: r._time, _value: r._value_mean})) |> yield(name: "mean")
j |> map(fn: (r) => ({_time: r._time, _value: r._value_shift})) |> yield(name: "shift")
j |> map(fn: (r) => ({_time: r._time, _value: r.diff})) |> yield(name: "diff")

Answer 3

The |> in TickScript "Declares a chaining method call which creates an instance of a new node and chains it to the node above it." as said in the official documentation