docs-v2/content/flux/v0/stdlib/experimental/diff.md

title	description	menu	weight	introduced
experimental.diff() function	`experimental.diff()` takes two table streams as input and produces a diff.	flux_v0_ref name parent identifier experimental.diff experimental experimental/diff	101	0.175.0

experimental.diff() takes two table streams as input and produces a diff.

experimental.diff() compares tables with the same group key. If compared tables are different, the function returns a table for that group key with one or more rows. If there are no differences, the function does not return a table for that group key.

Note: experimental.diff() cannot tell the difference between an empty table and a non-existent table.

Important: The output format of the diff is not considered stable and the algorithm used to produce the diff may change. The only guarantees are those mentioned above.

Function type signature

(<-got: stream[A], want: stream[A]) => stream[{A with _diff: string}]

{{% caption %}} For more information, see Function type signatures. {{% /caption %}}

Parameters

want

({{< req >}}) Input stream for the - side of the diff.

got

Input stream for the + side of the diff.

Examples

• Output a diff between two streams of tables
• Return a diff between a stream of tables and the expected output

Output a diff between two streams of tables

import "sampledata"
import "experimental"

want = sampledata.int()
got =
    sampledata.int()
        |> map(fn: (r) => ({r with _value: if r._value > 15 then r._value + 1 else r._value}))

experimental.diff(got: got, want: want)

{{< expand-wrapper >}} {{% expand "View example input" %}}

Input data

_diff	*tag	_time	_value
	t1	2021-01-01T00:00:00Z	-2
	t1	2021-01-01T00:00:10Z	10
	t1	2021-01-01T00:00:20Z	7
-	t1	2021-01-01T00:00:30Z	17
+	t1	2021-01-01T00:00:30Z	18
	t1	2021-01-01T00:00:40Z	15
	t1	2021-01-01T00:00:50Z	4

_diff	*tag	_time	_value
-	t2	2021-01-01T00:00:00Z	19
+	t2	2021-01-01T00:00:00Z	20
	t2	2021-01-01T00:00:10Z	4
	t2	2021-01-01T00:00:20Z	-3
-	t2	2021-01-01T00:00:30Z	19
+	t2	2021-01-01T00:00:30Z	20
	t2	2021-01-01T00:00:40Z	13
	t2	2021-01-01T00:00:50Z	1

{{% /expand %}} {{< /expand-wrapper >}}

Return a diff between a stream of tables and the expected output

import "experimental"

want = from(bucket: "backup-example-bucket") |> range(start: -5m)

from(bucket: "example-bucket")
    |> range(start: -5m)
    |> experimental.diff(want: want)