# InfluxDB Flux 常用 functions
## 基本查詢和序列操作
```javascript=
from(bucket: "quote")
|> range(start: v.timeRangeStart, stop:v.timeRangeStop)
|> filter(fn: (r) =>
r._measurement == "realtime" and
r.symbol == "${symbolSel}" and
r._field == "volume_24h"
)
```
### 兩個序列 join
```javascript=
join(tables: {t1: t1, t2: t2}, on: ["_time"])
|> map(fn: (r) => ({ r with _value: (r._value_t1 - r._value_t2)/r._value_t2 }))
|>map(fn: (r) => ({ r with alias: "120d 投資比" }))
```
### pivot 同序列不同欄位 join
```javascript=
|> pivot(rowKey:["_time"], columnKey: ["valmean"], valueColumn: "_value")
|> map(fn: (r) => ({ r with _value: r.volume / r.open }))
```
### union 聯集
```javascript=
union(tables: [t1, t2])
```
#### 透過 union 增加 fields
```javascript=
import "influxdata/influxdb/v1"
import "array"
extend_fields = array.from(rows: [{_value: "test"}])
exist_fields= v1.tagValues(
bucket: v.bucket,
tag: "_field",
predicate: (r) => r._measurement == "mark" and r._field != "h1sdQ2" and r._field != "m5sdQ2" ,
start: -1y
)
union(tables: [extend_fields, exist_fields])
```
### 今天到現在 range
```javascript=
import "date"
from(bucket: "quote")
|> range(start: duration(v: string(v: -date.hour(t: now())) +"h") )
```
### 取得最後15筆
```javascript=
|> sort(columns: [ "_time"],desc: true)
|> limit(n: 15)
```
### duplicate 欄位
```javascript=
|> duplicate(column: "tag", as: "tag_dup")
```
## 移動平均 / window 相關
### By 個數
```javascript=
|> movingAverage(n: 2 )
```
### By 時間
```javascript=
|> timedMovingAverage(every: 1y, period: 5y)
```
### 每一小平均
```javascript=
from(bucket: "quote")
|> range(start: v.timeRangeStart, stop:v.timeRangeStop)
|> filter(fn: (r) =>
r._measurement == "realtime" and
r.symbol == "ETH" and
r._field == "price"
)
|> window(every: 1h)
|> mean()
|> duplicate(column: "_stop", as: "_time")
|> window(every: inf)
```
## Time
### 時間粗化
```javascript=
import "date"
...
|> map(fn: (r) => ({ r with _time: date.truncate(t: r._time, unit: 1d) }))
```
### 一定時間內的Min / Max
```javascript=
t1 = from(bucket: "quote")
|> range(start: v.timeRangeStart, stop:v.timeRangeStop)
|> filter(fn: (r) =>
r._measurement == "realtime" and
r._field == "price" and
r.symbol == "${symbolSel}"
)
|> window(every: 1h)
|> max()
|> window(every: inf)
|> map(fn: (r) => ({ r with alias:"1h max" }))
t1
```
### 時間shift
```javascript=
|> timeShift(duration: 120d)
```
### 時間增加...用在range()
```javascript=
maShiftDuration= duration(v: "-"+string(v: (5*${y1_ma_n})) +"m")
ser= from(bucket: "quote")
|> range(start: date.add(d: maShiftDuration , to : v.timeRangeStart ) , stop:v.timeRangeStop)
...
```
## value function / map 常用
### IF ... Else...
```javascript=
|>map(fn: (r) => ({ r with alias: if r._field == "quote" then "Ordered-"+r.side else "StartOrder-"+r.side}))
```
### Math.abs
```javascript=
import "math"
math.abs(x: -1.22)
```
### findColumn Example
```javascript=
a= from(bucket: "quote")
|> range(start: v.timeRangeStart, stop:v.timeRangeStop)
|> filter(fn: (r) =>
r._measurement == "realtime" and
r.symbol == "${symbol}" and
r._field == "price"
)
|>max()
|> findColumn(
fn: (key) => key._field == "price",
column: "_value"
)
from(bucket: "quote")
|> range(start: v.timeRangeStart, stop:v.timeRangeStop)
|> filter(fn: (r) =>
r._measurement == "realtime" and
r.symbol == "${symbol}" and
r._field == "price"
)
|>map(fn: (r) => ({ r with _value: a[0] }))
```
## string
### string replace
```javascript=
import "strings"
...
|> movingAverage(n: int( v: strings.replaceAll(v: "${period}", t: "m", u: ""))/5 )
```
## object to stream
```javascript=
import "experimental"
import "array"
import "experimental/record"
user = {firstName: "John", lastName: "Doe", age: "42"}
dKeys= experimental.objectKeys(o: user)// Returns [firstName, lastName, age]
showKeys = dKeys |> array.map(fn: (x) => ({_value: x}))
showKV = dKeys |> array.map(fn: (x) => ({field: x , val : record.get(r: user, key: x, default: "") }))
array.from(rows: showKV )
```
###### tags: `influx` `grafana`
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