Documentation

experimental.join() function

experimental.join() is subject to change at any time.

experimental.join() joins two streams of tables on the group key and _time column.

Deprecated

experimental.join() is deprecated in favor of join.time(). The join package provides support for multiple join methods.

Use the fn parameter to map new output tables using values from input tables.

Note: To join streams of tables with different fields or measurements, use group() or drop() to remove _field and _measurement from the group key before joining.

Function type signature
(fn: (left: A, right: B) => C, left: stream[A], right: stream[B]) => stream[C] where A: Record, B: Record, C: Record
For more information, see Function type signatures.

Parameters

left

(Required) First of two streams of tables to join.

(Required) Second of two streams of tables to join.

fn

(Required) Function with left and right arguments that maps a new output record using values from the left and right input records. The return value must be a record.

Examples

Join two streams of tables

import "array"
import "experimental"

left =
    array.from(
        rows: [
            {_time: 2021-01-01T00:00:00Z, _field: "temp", _value: 80.1},
            {_time: 2021-01-01T01:00:00Z, _field: "temp", _value: 80.6},
            {_time: 2021-01-01T02:00:00Z, _field: "temp", _value: 79.9},
            {_time: 2021-01-01T03:00:00Z, _field: "temp", _value: 80.1},
        ],
    )
right =
    array.from(
        rows: [
            {_time: 2021-01-01T00:00:00Z, _field: "temp", _value: 75.1},
            {_time: 2021-01-01T01:00:00Z, _field: "temp", _value: 72.6},
            {_time: 2021-01-01T02:00:00Z, _field: "temp", _value: 70.9},
            {_time: 2021-01-01T03:00:00Z, _field: "temp", _value: 71.1},
        ],
    )

experimental.join(
    left: left,
    right: right,
    fn: (left, right) =>
        ({left with lv: left._value, rv: right._value, diff: left._value - right._value}),
)

View example output

Join two streams of tables with different fields and measurements

import "experimental"

s1 =
    from(bucket: "example-bucket")
        |> range(start: -1h)
        |> filter(fn: (r) => r._measurement == "foo" and r._field == "bar")
        |> group(columns: ["_time", "_measurement", "_field", "_value"], mode: "except")

s2 =
    from(bucket: "example-bucket")
        |> range(start: -1h)
        |> filter(fn: (r) => r._measurement == "baz" and r._field == "quz")
        |> group(columns: ["_time", "_measurement", "_field", "_value"], mode: "except")

experimental.join(
    left: s1,
    right: s2,
    fn: (left, right) => ({left with bar_value: left._value, quz_value: right._value}),
)

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