Documentation

Work with strings

A string type represents a sequence of characters. Strings are immutable and cannot be modified once created.

Type name: string

String syntax

A string literal is represented by a sequence of characters enclosed in double quotes ("). Any character may appear inside a string literal except an unescaped double quote. String literals support several escape sequences and hex encoding using \x as a prefix.

"abc"
"string with double \" quote"
"string with backslash \\"
"日本語"
"\xe6\x97\xa5\xe6\x9c\xac\xe8\xaa\x9e"

Convert data types to strings

Use the string() function to convert other basic types to strings:

  • boolean
  • bytes
  • duration
  • float
  • int
  • uint
  • time
string(v: 42)
// Returns "42"

Convert regular expressions to strings

To convert a regular expression to a string:

  1. Import the regexp package.
  2. Use regexp.getString() and provide the regular expression to convert to a string.
import "regexp"

regexp.getString(r: /[a-zA-Z]/)
// Returns [a-zA-Z] (string)

Convert data types to hexadecimal strings

To convert basic types to hexadecimal strings:

  1. Import the contrib/bonitoo-io/hex package.
  2. Use hex.string() to convert other a value to a hexadecimal string.
import "contrib/bonitoo-io/hex"

hex.string(v: 123456)
// Returns 1e240

Convert columns to strings

Flux lets you iterate over rows in a stream of tables and convert columns to strings.

To convert the _value column to strings, use the toString() function.

toString() only operates on the _value column.

data
    |> toString()
Given the following input data:
_time_value (int)
2021-01-01T00:00:00Z1
2021-01-01T02:00:00Z2
2021-01-01T03:00:00Z3
2021-01-01T04:00:00Z4
The example above returns:
_time_value (string)
2021-01-01T00:00:00Z1
2021-01-01T02:00:00Z2
2021-01-01T03:00:00Z3
2021-01-01T04:00:00Z4

To convert any column to strings:

  1. Use map() to iterate over and rewrite rows.
  2. Use string() to convert columns values to strings.
data
    |> map(fn: (r) => ({ r with level: string(v: r.level) }))
Given the following input data:
_timelevel (int)
2021-01-01T00:00:00Z1
2021-01-01T02:00:00Z2
2021-01-01T03:00:00Z3
2021-01-01T04:00:00Z4
The example above returns:
_timelevel (string)
2021-01-01T00:00:00Z1
2021-01-01T02:00:00Z2
2021-01-01T03:00:00Z3
2021-01-01T04:00:00Z4

Operate on strings

Use functions in the Flux strings package to perform operations including:

Interpolate strings

To interpolate strings in another Flux string, enclose embedded expressions in a dollar sign and curly braces ${}. Flux replaces the placeholder with the result of the embedded expression and returns a string literal.

name = "John"
"My name is ${name}."
// My name is John.

d = 1m
"the answer is ${d}"
// the answer is 1m

t0 = 2016-06-13T17:43:50Z
"the answer is ${t0}"
// the answer is 2016-06-13T17:43:50.000000000Z

p = {name: "John", age: 42}
"My name is ${p.name} and I'm ${p.age} years old."
// My name is John and I'm 42 years old.

String interpolation expressions must satisfy the Stringable constraint.

Concatenate strings

To concatenate Flux strings, use the + operator between string values or expressions that resolve to strings. Flux resolves expressions and returns a single concatenated string.

Concatenated expressions must resolve to strings.

name = "John"
"My name is " + name + "."
// My name is John.

d = 1m
"the answer is " + string(v: d)
// the answer is 1m

t0 = 2016-06-13T17:43:50Z
"the answer is " + string(v: t0)
// the answer is 2016-06-13T17:43:50.000000000Z

p = {name: "John", age: 42}
"My name is " + p.name + " and I'm " + string(v: p.age) + " years old."
// My name is John and I'm 42 years old.

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The future of Flux

Flux is going into maintenance mode. You can continue using it as you currently are without any changes to your code.

Flux is going into maintenance mode and will not be supported in InfluxDB 3.0. This was a decision based on the broad demand for SQL and the continued growth and adoption of InfluxQL. We are continuing to support Flux for users in 1.x and 2.x so you can continue using it with no changes to your code. If you are interested in transitioning to InfluxDB 3.0 and want to future-proof your code, we suggest using InfluxQL.

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