added flux tail function, resolves #374

pull/385/head
Scott Anderson 2019-08-09 14:42:32 -06:00
parent a31e9be735
commit 76dba6db64
2 changed files with 60 additions and 12 deletions

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@ -1,6 +1,6 @@
---
title: limit() function
description: The `limit()` function limits the number of records in output tables to a fixed number (n).
description: The `limit()` function limits records in each output table to the first `n` records.
aliases:
- /v2.0/reference/flux/functions/transformations/limit
menu:
@ -8,15 +8,17 @@ menu:
name: limit
parent: built-in-transformations
weight: 401
related:
- /v2.0/reference/flux/functions/built-in/transformations/tail/
- https://docs.influxdata.com/influxdb/latest/query_language/data_exploration/#the-limit-and-slimit-clauses, InfluxQL LIMIT
---
The `limit()` function limits the number of records in output tables to a fixed number ([`n`](#n)).
One output table is produced for each input table.
Each output table contains the first `n` records after the first `offset` records of the input table.
If the input table has less than `offset + n` records, all records except the first `offset` ones are output.
The `limit()` function limits records in each output table to the first [`n`](#n) records.
The function produces one output table for each input table.
Each output table contains the first `n` records after the [`offset`](#offset).
If the input table has less than `offset + n` records, `limit()` outputs all records after the `offset`.
_**Function type:** Filter_
_**Output data type:** Object_
_**Function type:** Filter_
```js
limit(n:10, offset: 0)
@ -41,8 +43,3 @@ from(bucket:"example-bucket")
|> range(start:-1h)
|> limit(n:10, offset: 1)
```
<hr style="margin-top:4rem"/>
##### Related InfluxQL functions and statements:
[LIMIT](https://docs.influxdata.com/influxdb/latest/query_language/data_exploration/#the-limit-and-slimit-clauses)

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---
title: tail() function
description: The `tail()` function limits records in each output table to the last `n` records.
menu:
v2_0_ref:
name: tail
parent: built-in-transformations
weight: 401
related:
- /v2.0/reference/flux/functions/built-in/transformations/limit/
---
The `tail()` function limits records in each output table to the last [`n`](#n) records.
The function produces one output table for each input table.
Each output table contains the last `n` records before the [`offset`](#offset).
If the input table has less than `offset + n` records, `tail()` outputs all records before the `offset`.
_**Function type:** Filter_
```js
tail(n:10, offset: 0)
```
## Parameters
### n
The maximum number of records to output.
_**Data type:** Integer_
### offset
The number of records to skip at the end of a table table before limiting to `n`.
Defaults to `0`.
_**Data type:** Integer_
## Examples
##### Output the last ten records in each table
```js
from(bucket:"example-bucket")
|> range(start:-1h)
|> tail(n:10)
```
##### Output the last ten records in each table
```js
from(bucket:"example-bucket")
|> range(start:-1h)
|> tail(n:5, offset: 1)
```