189 lines
6.3 KiB
Markdown
189 lines
6.3 KiB
Markdown
---
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title: keys() function
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description: >
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`keys()` returns the columns that are in the group key of each input table.
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menu:
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flux_v0_ref:
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name: keys
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parent: universe
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identifier: universe/keys
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weight: 101
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flux/v0/tags: [transformations]
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introduced: 0.13.0
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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/universe/universe.flux#L1610-L1610
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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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`keys()` returns the columns that are in the group key of each input table.
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Each output table contains a row for each group key column label.
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A single group key column label is stored in the specified `column` for each row.
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All columns not in the group key are dropped.
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##### Function type signature
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```js
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(<-tables: stream[A], ?column: string) => stream[B] where A: Record, B: 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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### column
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Column to store group key labels in. Default is `_value`.
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### tables
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Input data. Default is piped-forward data (`<-`).
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## Examples
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- [Return group key columns for each input table](#return-group-key-columns-for-each-input-table)
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- [Return all distinct group key columns in a single table](#return-all-distinct-group-key-columns-in-a-single-table)
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- [Return group key columns as an array](#return-group-key-columns-as-an-array)
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### Return group key columns for each input table
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```js
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data
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|> keys()
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```
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{{< expand-wrapper >}}
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{{% expand "View example input and output" %}}
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#### Input data
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| *_field | *_measurement | *sensorID | _time | _value |
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| ------- | ------------- | --------- | -------------------- | ------- |
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| co | airSensors | TLM0100 | 2021-09-08T14:21:57Z | 0.31 |
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| co | airSensors | TLM0100 | 2021-09-08T14:22:07Z | 0.295 |
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| co | airSensors | TLM0100 | 2021-09-08T14:22:17Z | 0.314 |
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| co | airSensors | TLM0100 | 2021-09-08T14:22:27Z | 0.313 |
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| *_field | *_measurement | *sensorID | _time | _value |
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| -------- | ------------- | --------- | -------------------- | ------- |
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| humidity | airSensors | TLM0100 | 2021-09-08T14:21:57Z | 36.03 |
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| humidity | airSensors | TLM0100 | 2021-09-08T14:22:07Z | 36.07 |
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| humidity | airSensors | TLM0100 | 2021-09-08T14:22:17Z | 36.1 |
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| humidity | airSensors | TLM0100 | 2021-09-08T14:22:27Z | 36.12 |
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| *_field | *_measurement | *sensorID | _time | _value |
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| ----------- | ------------- | --------- | -------------------- | ------- |
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| temperature | airSensors | TLM0100 | 2021-09-08T14:21:57Z | 70.84 |
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| temperature | airSensors | TLM0100 | 2021-09-08T14:22:07Z | 70.86 |
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| temperature | airSensors | TLM0100 | 2021-09-08T14:22:17Z | 70.89 |
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| temperature | airSensors | TLM0100 | 2021-09-08T14:22:27Z | 70.85 |
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#### Output data
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| *_field | *_measurement | *sensorID | _value |
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| ------- | ------------- | --------- | ------------ |
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| co | airSensors | TLM0100 | _field |
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| co | airSensors | TLM0100 | _measurement |
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| co | airSensors | TLM0100 | sensorID |
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| *_field | *_measurement | *sensorID | _value |
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| -------- | ------------- | --------- | ------------ |
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| humidity | airSensors | TLM0100 | _field |
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| humidity | airSensors | TLM0100 | _measurement |
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| humidity | airSensors | TLM0100 | sensorID |
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| *_field | *_measurement | *sensorID | _value |
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| ----------- | ------------- | --------- | ------------ |
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| temperature | airSensors | TLM0100 | _field |
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| temperature | airSensors | TLM0100 | _measurement |
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| temperature | airSensors | TLM0100 | sensorID |
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{{% /expand %}}
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{{< /expand-wrapper >}}
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### Return all distinct group key columns in a single table
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```js
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data
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|> keys()
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|> keep(columns: ["_value"])
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|> distinct()
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```
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{{< expand-wrapper >}}
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{{% expand "View example input and output" %}}
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#### Input data
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| *_field | *_measurement | *sensorID | _time | _value |
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| ------- | ------------- | --------- | -------------------- | ------- |
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| co | airSensors | TLM0100 | 2021-09-08T14:21:57Z | 0.31 |
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| co | airSensors | TLM0100 | 2021-09-08T14:22:07Z | 0.295 |
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| co | airSensors | TLM0100 | 2021-09-08T14:22:17Z | 0.314 |
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| co | airSensors | TLM0100 | 2021-09-08T14:22:27Z | 0.313 |
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| *_field | *_measurement | *sensorID | _time | _value |
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| -------- | ------------- | --------- | -------------------- | ------- |
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| humidity | airSensors | TLM0100 | 2021-09-08T14:21:57Z | 36.03 |
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| humidity | airSensors | TLM0100 | 2021-09-08T14:22:07Z | 36.07 |
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| humidity | airSensors | TLM0100 | 2021-09-08T14:22:17Z | 36.1 |
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| humidity | airSensors | TLM0100 | 2021-09-08T14:22:27Z | 36.12 |
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| *_field | *_measurement | *sensorID | _time | _value |
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| ----------- | ------------- | --------- | -------------------- | ------- |
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| temperature | airSensors | TLM0100 | 2021-09-08T14:21:57Z | 70.84 |
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| temperature | airSensors | TLM0100 | 2021-09-08T14:22:07Z | 70.86 |
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| temperature | airSensors | TLM0100 | 2021-09-08T14:22:17Z | 70.89 |
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| temperature | airSensors | TLM0100 | 2021-09-08T14:22:27Z | 70.85 |
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#### Output data
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| _value |
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| ------------ |
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| _field |
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| _measurement |
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| sensorID |
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{{% /expand %}}
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{{< /expand-wrapper >}}
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### Return group key columns as an array
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1. Use `keys()` to replace the `_value` column with the group key labels.
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2. Use `findColumn()` to return the `_value` column as an array.
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```js
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import "sampledata"
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sampledata.int()
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|> keys()
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|> findColumn(fn: (key) => true, column: "_value")// Returns [tag]
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```
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