120 lines
3.3 KiB
Markdown
120 lines
3.3 KiB
Markdown
---
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title: join.inner() function
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description: >
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`join.inner()` performs an inner join on two table streams.
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menu:
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flux_v0_ref:
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name: join.inner
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parent: join
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identifier: join/inner
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weight: 101
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flux/v0/tags: [transformations]
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introduced: 0.172.0
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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/join/join.flux#L311-L318
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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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`join.inner()` performs an inner join on two table streams.
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The function calls `join.tables()` with the `method` parameter set to `"inner"`.
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##### Function type signature
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```js
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(<-left: stream[A], as: (l: A, r: B) => C, on: (l: A, r: B) => bool, right: stream[B]) => stream[C] where A: Record, B: Record, C: Record
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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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### left
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Left input stream. Default is piped-forward data (<-).
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### right
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({{< req >}})
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Right input stream.
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### on
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({{< req >}})
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Function that takes a left and right record (`l`, and `r` respectively), and returns a boolean.
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The body of the function must be a single boolean expression, consisting of one
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or more equality comparisons between a property of `l` and a property of `r`,
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each chained together by the `and` operator.
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### as
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({{< req >}})
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Function that takes a left and a right record (`l` and `r` respectively), and returns a record.
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The returned record is included in the final output.
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## Examples
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### Perform an inner join
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```js
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import "sampledata"
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import "join"
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ints = sampledata.int()
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strings = sampledata.string()
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join.inner(
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left: ints,
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right: strings,
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on: (l, r) => l._time == r._time,
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as: (l, r) => ({l with label: r._value}),
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)
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```
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{{< expand-wrapper >}}
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{{% expand "View example output" %}}
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#### Output data
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| _time | _value | label | *tag |
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| -------------------- | ------- | ----------- | ---- |
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| 2021-01-01T00:00:00Z | -2 | smpl_g9qczs | t1 |
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| 2021-01-01T00:00:10Z | 10 | smpl_0mgv9n | t1 |
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| 2021-01-01T00:00:20Z | 7 | smpl_phw664 | t1 |
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| 2021-01-01T00:00:30Z | 17 | smpl_guvzy4 | t1 |
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| 2021-01-01T00:00:40Z | 15 | smpl_5v3cce | t1 |
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| 2021-01-01T00:00:50Z | 4 | smpl_s9fmgy | t1 |
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| _time | _value | label | *tag |
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| -------------------- | ------- | ----------- | ---- |
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| 2021-01-01T00:00:00Z | 19 | smpl_b5eida | t2 |
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| 2021-01-01T00:00:10Z | 4 | smpl_eu4oxp | t2 |
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| 2021-01-01T00:00:20Z | -3 | smpl_5g7tz4 | t2 |
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| 2021-01-01T00:00:30Z | 19 | smpl_sox1ut | t2 |
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| 2021-01-01T00:00:40Z | 13 | smpl_wfm757 | t2 |
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| 2021-01-01T00:00:50Z | 1 | smpl_dtn2bv | t2 |
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{{% /expand %}}
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{{< /expand-wrapper >}}
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