time.Parse in Go 具有不同的小数秒长度

Question

I am parsing a timestamp from a DB. My layout is the following:

layout = "2006-01-02 15:04:05.000000000 -0700 MST"

pipelineTS, err := time.Parse(layout, rawPipelineTS)

The issue is that sometimes the fractional seconds are not 9 digits, for example:

2018-12-18 15:25:08.73728596 +0000 UTC  

When it finds a value like this, it errors out. Any ideas on how to fix this? The timestamps come from a DB table. I need it to take any number of fractional second digits.

Answer 1

Package time

A decimal point followed by one or more zeros represents a fractional second, printed to the given number of decimal places. A decimal point followed by one or more nines represents a fractional second, printed to the given number of decimal places, with trailing zeros removed.

---

Use nines, not zeros, for the layout fractional seconds.

For example,

package main

import (
    "fmt"
    "time"
)

func main() {
    layout := "2006-01-02 15:04:05.999999999 -0700 MST"

    input := "2018-12-18 15:25:08.73728596 +0000 UTC" // 8 digits
    t, err := time.Parse(layout, input)
    fmt.Println(t, err)

    input = "2018-12-18 15:25:08.7372 +0000 UTC" // 4 digits
    t, err = time.Parse(layout, input)
    fmt.Println(t, err)

    input = "2018-12-18 15:25:08 +0000 UTC" // 0 digits
    t, err = time.Parse(layout, input)
    fmt.Println(t, err)
}

Playground: https://play.golang.org/p/j4WBmz3ENke

Output:

2018-12-18 15:25:08.73728596 +0000 UTC <nil>
2018-12-18 15:25:08.7372 +0000 UTC <nil>
2018-12-18 15:25:08 +0000 UTC <nil>

Answer 2

From the time docs:

A decimal point followed by one or more zeros represents a fractional second, printed to the given number of decimal places. A decimal point followed by one or more nines represents a fractional second, printed to the given number of decimal places, with trailing zeros removed. When parsing (only), the input may contain a fractional second field immediately after the seconds field, even if the layout does not signify its presence. In that case a decimal point followed by a maximal series of digits is parsed as a fractional second.

For time parsing:

1. If you don't specify fractional seconds in the layout, time.Parse will still accept it in the input, with full resolution (the "maximal series of digits"). ( source )
2. If you specify fractional seconds with one or more zeros, time.Parse requires the input to have that exact number of fractional digits. ( source )
3. If you specify fractional seconds with one or more nines, time.Parse actually accepts any number of fractional digits (up to 9). That is, the behavior is the same as if you didn't specify fractional seconds at all (case #1). I think the docs are not clear on this point at all, but for parsing (not formatting), .9 , .99 , .999 , .999999 , etc. are all exactly equivalent. ( source )

Playground samples: https://play.golang.org/p/aXYiaMsCVuz