Flux vs InfluxQL

Flux is an alternative to InfluxQL and other SQL-like query languages for querying and analyzing data. Flux uses functional language patterns making it incredibly powerful, flexible, and able to overcome many of the limitations of InfluxQL. This article outlines many of the tasks possible with Flux but not InfluxQL and provides information about Flux and InfluxQL parity.

• Possible with Flux
• InfluxQL and Flux parity

Possible with Flux

• Joins
• Math across measurements
• Sort by tags
• Group by any column
• Window by calendar months and years
• Work with multiple data sources
• DatePart-like queries
• Pivot
• Histograms
• Covariance
• Cast booleans to integers
• String manipulation and data shaping
• Work with geo-temporal data

Joins

InfluxQL has never supported joins. They can be accomplished using TICKscript, but even TICKscript’s join capabilities are limited. Flux’s join() function lets you to join data from any bucket, any measurement, and on any columns as long as each data set includes the columns on which they are to be joined. This opens the door for really powerful and useful operations.

dataStream1 = from(bucket: "bucket1")
    |> range(start: -1h)
    |> filter(fn: (r) => r._measurement == "network" and r._field == "bytes-transferred")

dataStream2 = from(bucket: "bucket1")
    |> range(start: -1h)
    |> filter(fn: (r) => r._measurement == "httpd" and r._field == "requests-per-sec")

join(tables: {d1: dataStream1, d2: dataStream2}, on: ["_time", "_stop", "_start", "host"])

For an in-depth walkthrough of using the join() function, see How to join data with Flux.

Math across measurements

Being able to perform cross-measurement joins also allows you to run calculations using data from separate measurements – a highly requested feature from the InfluxData community. The example below takes two data streams from separate measurements, mem and processes, joins them, then calculates the average amount of memory used per running process:

// Memory used (in bytes)
memUsed = from(bucket: "telegraf/autogen")
    |> range(start: -1h)
    |> filter(fn: (r) => r._measurement == "mem" and r._field == "used")

// Total processes running
procTotal = from(bucket: "telegraf/autogen")
    |> range(start: -1h)
    |> filter(fn: (r) => r._measurement == "processes" and r._field == "total")

// Join memory used with total processes and calculate
// the average memory (in MB) used for running processes.
join(tables: {mem: memUsed, proc: procTotal}, on: ["_time", "_stop", "_start", "host"])
    |> map(fn: (r) => ({_time: r._time, _value: r._value_mem / r._value_proc / 1000000}))

Sort by tags

InfluxQL’s sorting capabilities are very limited, allowing you only to control the sort order of time using the ORDER BY time clause. Flux’s sort() function sorts records based on list of columns. Depending on the column type, records are sorted lexicographically, numerically, or chronologically.

from(bucket: "telegraf/autogen")
    |> range(start: -12h)
    |> filter(fn: (r) => r._measurement == "system" and r._field == "uptime")
    |> sort(columns: ["region", "host", "_value"])

Group by any column

InfluxQL lets you group by tags or by time intervals, but nothing else. Flux lets you group by any column in the dataset, including _value. Use the Flux group() function to define which columns to group data by.

from(bucket:"telegraf/autogen")
    |> range(start:-12h)
    |> filter(fn: (r) => r._measurement == "system" and r._field == "uptime" )
    |> group(columns:["host", "_value"])

Window by calendar months and years

InfluxQL does not support windowing data by calendar months and years due to their varied lengths. Flux supports calendar month and year duration units (1mo, 1y) and lets you window and aggregate data by calendar month and year.

from(bucket:"telegraf/autogen")
    |> range(start:-1y)
    |> filter(fn: (r) => r._measurement == "mem" and r._field == "used_percent" )
    |> aggregateWindow(every: 1mo, fn: mean)

Work with multiple data sources

InfluxQL can only query data stored in InfluxDB. Flux can query data from other data sources such as CSV, PostgreSQL, MySQL, Google BigTable, and more. Join that data with data in InfluxDB to enrich query results.

• Flux CSV package
• Flux SQL package
• Flux BigTable package

import "csv"
import "sql"

csvData = csv.from(csv: rawCSV)
sqlData = sql.from(
    driverName: "postgres",
    dataSourceName: "postgresql://user:password@localhost",
    query: "SELECT * FROM example_table",
)
data = from(bucket: "telegraf/autogen")
    |> range(start: -24h)
    |> filter(fn: (r) => r._measurement == "sensor")

auxData = join(tables: {csv: csvData, sql: sqlData}, on: ["sensor_id"])
enrichedData = join(tables: {data: data, aux: auxData}, on: ["sensor_id"])

enrichedData
    |> yield(name: "enriched_data")

For an in-depth walkthrough of querying SQL data, see Query SQL data sources.

DatePart-like queries

InfluxQL doesn’t support DatePart-like queries that only return results during specified hours of the day. The Flux hourSelection function returns only data with time values in a specified hour range.

from(bucket: "telegraf/autogen")
    |> range(start: -1h)
    |> filter(fn: (r) => r._measurement == "cpu" and r.cpu == "cpu-total")
    |> hourSelection(start: 9, stop: 17)

Pivot

Pivoting data tables has never been supported in InfluxQL. The Flux pivot() function provides the ability to pivot data tables by specifying rowKey, columnKey, and valueColumn parameters.

from(bucket: "telegraf/autogen")
    |> range(start: -1h)
    |> filter(fn: (r) => r._measurement == "cpu" and r.cpu == "cpu-total")
    |> pivot(rowKey: ["_time"], columnKey: ["_field"], valueColumn: "_value")

Histograms

The ability to generate histograms has been a highly requested feature for InfluxQL, but has never been supported. Flux’s histogram() function uses input data to generate a cumulative histogram with support for other histogram types coming in the future.

from(bucket: "telegraf/autogen")
    |> range(start: -1h)
    |> filter(fn: (r) => r._measurement == "mem" and r._field == "used_percent")
    |> histogram(buckets: [10, 20, 30, 40, 50, 60, 70, 80, 90, 100,])

For an example of using Flux to create a cumulative histogram, see Create histograms.

Covariance

Flux provides functions for simple covariance calculation. The covariance() function calculates the covariance between two columns and the cov() function calculates the covariance between two data streams.

Covariance between two columns

from(bucket: "telegraf/autogen")
    |> range(start: -5m)
    |> covariance(columns: ["x", "y"])

Covariance between two streams of data

table1 = from(bucket: "telegraf/autogen")
    |> range(start: -15m)
    |> filter(fn: (r) => r._measurement == "measurement_1")

table2 = from(bucket: "telegraf/autogen")
    |> range(start: -15m)
    |> filter(fn: (r) => r._measurement == "measurement_2")

cov(x: table1, y: table2, on: ["_time", "_field"])

Cast booleans to integers

InfluxQL supports type casting, but only for numeric data types (floats to integers and vice versa). Flux type conversion functions provide much broader support for type conversions and let you perform some long-requested operations like casting a boolean values to integers.

Cast boolean field values to integers

from(bucket: "telegraf/autogen")
    |> range(start: -1h)
    |> filter(fn: (r) => r._measurement == "m" and r._field == "bool_field")
    |> toInt()

String manipulation and data shaping

InfluxQL doesn’t support string manipulation when querying data. The Flux Strings package is a collection of functions that operate on string data. When combined with the map() function, functions in the string package allow for operations like string sanitization and normalization.

import "strings"

from(bucket: "telegraf/autogen")
    |> range(start: -1h)
    |> filter(fn: (r) => r._measurement == "weather" and r._field == "temp")
    |> map(
        fn: (r) => ({
            r with
            location: strings.toTitle(v: r.location),
            sensor: strings.replaceAll(v: r.sensor, t: " ", u: "-"),
            status: strings.substring(v: r.status, start: 0, end: 8),
        })
    )

Work with geo-temporal data

InfluxQL doesn’t provide functionality for working with geo-temporal data. The Flux Geo package is a collection of functions that let you shape, filter, and group geo-temporal data.

import "experimental/geo"

from(bucket: "geo/autogen")
    |> range(start: -1w)
    |> filter(fn: (r) => r._measurement == "taxi")
    |> geo.shapeData(latField: "latitude", lonField: "longitude", level: 20)
    |> geo.filterRows(region: {lat: 40.69335938, lon: -73.30078125, radius: 20.0}, strict: true)
    |> geo.asTracks(groupBy: ["fare-id"])

InfluxQL and Flux parity

Flux is working towards complete parity with InfluxQL and new functions are being added to that end. The table below shows InfluxQL statements, clauses, and functions along with their equivalent Flux functions.

For a complete list of Flux functions, view all Flux functions.

InfluxQL and Flux parity

* The to() function only writes to InfluxDB 2.0.