added rows papckage and rows.map function
Scott Anderson
parent
4c4177e9c7
commit
fa2f15af70
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@ -13,6 +13,7 @@ influxdb/v2.0/tags: [exists]
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related:
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- /influxdb/v2.0/query-data/flux/conditional-logic/
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- /influxdb/v2.0/query-data/flux/mathematic-operations/
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- /influxdb/v2.0/reference/flux/stdlib/contrib/rows/map/
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---
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The `map()` function applies a function to each record in the input tables.
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@ -22,8 +23,7 @@ The output tables are the result of applying the map function to each record of
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When the output record contains a different value for the group key, the record is regrouped into the appropriate table.
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When the output record drops a column that was part of the group key, that column is removed from the group key.
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_**Function type:** Transformation_
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_**Output data type:** Object_
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_**Function type:** Transformation_
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```js
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map(fn: (r) => ({ _value: r._value * r._value }))
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@ -37,7 +37,7 @@ Make sure `fn` parameter names match each specified parameter. To learn why, see
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### fn
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A single argument function that to apply to each record.
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A single argument function to apply to each record.
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The return value must be an object.
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_**Data type:** Function_
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@ -0,0 +1,28 @@
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---
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title: Flux Rows package
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list_title: Rows package
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description: >
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The Flux Rows package provides additional functions for remapping values in rows.
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Import the `contrib/jsternberg/rows` package.
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menu:
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v2_0_ref:
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name: Rows
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parent: Contributed
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weight: 202
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v2.0/tags: [functions, package]
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---
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The Flux Rows package provides additional functions for remapping values in rows.
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Import the `contrib/jsternberg/rows` package:
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```js
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import "contrib/jsternberg/rows"
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```
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{{< children type="functions" show="pages" >}}
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{{% note %}}
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#### Package author and maintainer
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**Github:** [@jsternberg](https://github.com/jsternberg)
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**InfluxDB Slack:** [@Jonathan Sternberg](https://influxdata.com/slack)
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{{% /note %}}
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@ -0,0 +1,223 @@
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---
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title: rows.map() function
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description: >
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The `rows.map()` function is an alternate implementation of [`map()`](/v2.0/reference/flux/stdlib/built-in/transformations/map/)
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that is faster, but more limited than `map()`.
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menu:
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v2_0_ref:
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name: rows.map
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parent: Rows
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weight: 202
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v2.0/tags: [functions, package, map]
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related:
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- /v2.0/reference/flux/stdlib/built-in/transformations/map/
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---
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The `rows.map()` function is an alternate implementation of [`map()`](/v2.0/reference/flux/stdlib/built-in/transformations/map/)
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that is faster, but more limited than `map()`.
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`rows.map()` cannot modify table groups key and, therefore, does not need to regroup tables.
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**Attempts to change columns in the group key are ignored.**
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_**Function type:** Transformation_
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```js
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import "contrib/jsternberg/rows"
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rows.map( fn: (r) => ({_value: r._value * 100.0}))
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```
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## Parameters
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### fn
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A single argument function to apply to each record.
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The return value must be an object.
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_**Data type:** Function_
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{{% note %}}
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Use the `with` operator to preserve columns **not** in the group and **not**
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explicitly mapped in the operation.
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{{% /note %}}
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## Examples
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The examples below use a `data` variable that represents the following input tables:
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---
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### Perform mathemtical operations on column values
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The following example returns the square of each value in the `_value` column:
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```js
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import "contrib/jsternberg/rows"
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data
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|> rows.map(fn: (r) ({ _value: r._value * r._value }))
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```
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{{% note %}}
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#### Important notes
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The `_time` column is dropped because:
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- It's not in the group key.
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- It's not explicitly mapped in the operation.
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- The `with` operator was not used to include existing columns.
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{{% /note %}}
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{{< flex >}}
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{{% flex-content %}}
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#### Input tables
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**Group key:** `tag,_field`
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| tag | _field | _time | _value |
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|:--- |:------ |:----- | ------:|
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| tag1 | foo | 0001 | 1.9 |
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| tag1 | foo | 0002 | 2.4 |
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| tag1 | foo | 0003 | 2.1 |
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| tag | _field | _time | _value |
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|:--- |:------ |:----- | ------:|
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| tag2 | bar | 0001 | 3.1 |
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| tag2 | bar | 0002 | 3.8 |
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| tag2 | bar | 0003 | 1.7 |
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{{% /flex-content %}}
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{{% flex-content %}}
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#### Output tables
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**Group key:** `tag,_field`
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| tag | _field | _value |
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|:--- |:------ | ------:|
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| tag1 | foo | 3.61 |
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| tag1 | foo | 5.76 |
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| tag1 | foo | 4.41 |
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| tag | _field | _value |
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|:--- |:------ | ------:|
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| tag2 | bar | 9.61 |
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| tag2 | bar | 14.44 |
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| tag2 | bar | 2.89 |
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{{% /flex-content %}}
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{{< /flex >}}
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---
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### Preserve all columns in the operation
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Use the `with` operator in your mapping operation to preserve all columns,
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including those not in the group key, without explicitly remapping them.
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```js
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import "contrib/jsternberg/rows"
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data
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|> rows.map(fn: (r) ({ r with _value: r._value * r._value }))
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```
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{{% note %}}
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#### Important notes
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- The mapping operation remaps the `_value` column.
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- The `with` operator preserves all other columns not in the group key (`_time`).
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{{% /note %}}
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{{< flex >}}
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{{% flex-content %}}
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#### Input tables
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**Group key:** `tag,_field`
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| tag | _field | _time | _value |
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|:--- |:------ |:----- | ------:|
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| tag1 | foo | 0001 | 1.9 |
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| tag1 | foo | 0002 | 2.4 |
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| tag1 | foo | 0003 | 2.1 |
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| tag | _field | _time | _value |
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|:--- |:------ |:----- | ------:|
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| tag2 | bar | 0001 | 3.1 |
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| tag2 | bar | 0002 | 3.8 |
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| tag2 | bar | 0003 | 1.7 |
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{{% /flex-content %}}
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{{% flex-content %}}
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#### Output tables
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**Group key:** `tag,_field`
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| tag | _field | _time | _value |
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|:--- |:------ |:----- | ------:|
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| tag1 | foo | 0001 | 3.61 |
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| tag1 | foo | 0002 | 5.76 |
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| tag1 | foo | 0003 | 4.41 |
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| tag | _field | _time | _value |
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|:--- |:------ |:----- | ------:|
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| tag2 | bar | 0001 | 9.61 |
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| tag2 | bar | 0002 | 14.44 |
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| tag2 | bar | 0003 | 2.89 |
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{{% /flex-content %}}
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{{< /flex >}}
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---
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### Attempt to remap columns in the group key
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```js
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import "contrib/jsternberg/rows"
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data
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|> rows.map(fn: (r) ({ r with tag: "tag3" }))
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```
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{{% note %}}
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#### Important notes
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- Remapping the `tag` column to `"tag3"` is ignored because `tag` is part of the group key.
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- The `with` operator preserves columns not in the group key (`_time` and `_value`).
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{{% /note %}}
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{{< flex >}}
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{{% flex-content %}}
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#### Input tables
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**Group key:** `tag,_field`
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| tag | _field | _time | _value |
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|:--- |:------ |:----- | ------:|
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| tag1 | foo | 0001 | 1.9 |
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| tag1 | foo | 0002 | 2.4 |
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| tag1 | foo | 0003 | 2.1 |
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| tag | _field | _time | _value |
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|:--- |:------ |:----- | ------:|
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| tag2 | bar | 0001 | 3.1 |
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| tag2 | bar | 0002 | 3.8 |
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| tag2 | bar | 0003 | 1.7 |
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{{% /flex-content %}}
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{{% flex-content %}}
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#### Output tables
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**Group key:** `tag,_field`
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| tag | _field | _time | _value |
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|:--- |:------ |:----- | ------:|
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| tag1 | foo | 0001 | 1.9 |
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| tag1 | foo | 0002 | 2.4 |
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| tag1 | foo | 0003 | 2.1 |
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| tag | _field | _time | _value |
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|:--- |:------ |:----- | ------:|
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| tag2 | bar | 0001 | 3.1 |
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| tag2 | bar | 0002 | 3.8 |
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| tag2 | bar | 0003 | 1.7 |
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{{% /flex-content %}}
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{{< /flex >}}
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---
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{{% note %}}
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#### Package author and maintainer
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**Github:** [@jsternberg](https://github.com/jsternberg)
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**InfluxDB Slack:** [@Jonathan Sternberg](https://influxdata.com/slack)
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{{% /note %}}
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