129 lines
3.8 KiB
Markdown
129 lines
3.8 KiB
Markdown
---
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title: experimental.diff() function
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description: >
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`experimental.diff()` takes two table streams as input and produces a diff.
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menu:
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flux_v0_ref:
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name: experimental.diff
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parent: experimental
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identifier: experimental/diff
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weight: 101
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introduced: 0.175.0
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---
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<!------------------------------------------------------------------------------
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IMPORTANT: This page was generated from comments in the Flux source code. Any
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edits made directly to this page will be overwritten the next time the
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documentation is generated.
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To make updates to this documentation, update the function comments above the
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function definition in the Flux source code:
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https://github.com/influxdata/flux/blob/master/stdlib/experimental/experimental.flux#L1420-L1420
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Contributing to Flux: https://github.com/influxdata/flux#contributing
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Fluxdoc syntax: https://github.com/influxdata/flux/blob/master/docs/fluxdoc.md
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------------------------------------------------------------------------------->
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`experimental.diff()` takes two table streams as input and produces a diff.
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`experimental.diff()` compares tables with the same group key.
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If compared tables are different, the function returns a table for that group key with one or more rows.
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If there are no differences, the function does not return a table for that group key.
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**Note:** `experimental.diff()` cannot tell the difference between an empty table and a non-existent table.
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**Important:** The output format of the diff is not considered stable and the algorithm used to produce the diff may change.
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The only guarantees are those mentioned above.
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##### Function type signature
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```js
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(<-got: stream[A], want: stream[A]) => stream[{A with _diff: string}]
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```
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{{% caption %}}
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For more information, see [Function type signatures](/flux/v0/function-type-signatures/).
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{{% /caption %}}
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## Parameters
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### want
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({{< req >}})
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Input stream for the `-` side of the diff.
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### got
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Input stream for the `+` side of the diff.
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## Examples
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- [Output a diff between two streams of tables](#output-a-diff-between-two-streams-of-tables)
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- [Return a diff between a stream of tables and the expected output](#return-a-diff-between-a-stream-of-tables-and-the-expected-output)
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### Output a diff between two streams of tables
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```js
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import "sampledata"
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import "experimental"
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want = sampledata.int()
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got =
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sampledata.int()
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|> map(fn: (r) => ({r with _value: if r._value > 15 then r._value + 1 else r._value}))
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experimental.diff(got: got, want: want)
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```
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{{< expand-wrapper >}}
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{{% expand "View example input" %}}
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#### Input data
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| _diff | *tag | _time | _value |
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| ------ | ---- | -------------------- | ------- |
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| | t1 | 2021-01-01T00:00:00Z | -2 |
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| | t1 | 2021-01-01T00:00:10Z | 10 |
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| | t1 | 2021-01-01T00:00:20Z | 7 |
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| - | t1 | 2021-01-01T00:00:30Z | 17 |
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| + | t1 | 2021-01-01T00:00:30Z | 18 |
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| | t1 | 2021-01-01T00:00:40Z | 15 |
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| | t1 | 2021-01-01T00:00:50Z | 4 |
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| _diff | *tag | _time | _value |
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| ------ | ---- | -------------------- | ------- |
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| - | t2 | 2021-01-01T00:00:00Z | 19 |
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| + | t2 | 2021-01-01T00:00:00Z | 20 |
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| | t2 | 2021-01-01T00:00:10Z | 4 |
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| | t2 | 2021-01-01T00:00:20Z | -3 |
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| - | t2 | 2021-01-01T00:00:30Z | 19 |
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| + | t2 | 2021-01-01T00:00:30Z | 20 |
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| | t2 | 2021-01-01T00:00:40Z | 13 |
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| | t2 | 2021-01-01T00:00:50Z | 1 |
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{{% /expand %}}
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{{< /expand-wrapper >}}
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### Return a diff between a stream of tables and the expected output
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```js
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import "experimental"
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want = from(bucket: "backup-example-bucket") |> range(start: -5m)
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from(bucket: "example-bucket")
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|> range(start: -5m)
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|> experimental.diff(want: want)
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```
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