How to get timestamp value out of Postgresql without time zone? - postgresql

Question

I have a table with timestamp TIMESTAMP, data TEXT columns. I have a failing test because I can't get a timestamp value out of postgresql without time zone annotation. Here's an abridged version of what I've done in my Go application:
type Datapoint struct {
Timestamp string
Data sql.NullString
}
var testData = Datapoint{Timestamp:'2018-12-31 00:00:00', Data:'test'}
db.Exec("CREATE TABLE mytable (id SERIAL, timestamp TIMESTAMP, data TEXT);")
db.Exec("INSERT INTO mytable(timestamp, data) VALUES ($1, $2);", testData.Timestamp, testData.Data)
datapoints, err = db.Exec("SELECT timestamp::TIMESTAMP WITHOUT TIME ZONE, data FROM mytable;")
This trouble is that this query (after about 20 lines of error checking and row.Scan; golang's a bit verbose like that...) gives me:
expected 2018-12-31 00:00:00, received 2018-12-31T00:00:00Z
I requested without timezone (and the query succeeds in psql), so why am I getting the extra T and Z in the string?

Answer 1

Scan into a value of time.Time instead of string, then you can format the time as desired.
package main
import (
"database/sql"
"fmt"
"log"
"time"
)
type Datapoint struct {
Timestamp time.Time
Data sql.NullString
}
func main() {
var db *sql.DB
var dp Datapoint
err := db.QueryRow("SELECT timestamp, data FROM mytable").Scan(
&dp.Timestamp, &dp.Data,
)
switch {
case err == sql.ErrNoRows:
log.Fatal("No rows")
case err != nil:
log.Fatal(err)
default:
fmt.Println(dp.Timestamp.Format("2006-01-02 15:04:05"))
}
}

Answer 2

What you are receiving is an ISO 8601 representation of time.
T is the time designator that precedes the time components of the representation.
Z is used to represent that it is in UTC time, with Z representing zero offset.
In a way you are getting something without a timezone but it can be confusing, especially as you haven't localised your time at any point. I would suggest you consider using ISO times, or you could convert your time to a string like this
s := fmt.Sprintf("%d-%02d-%02d %02d:%02d:%02d\n",
t.Year(), t.Month(), t.Day(),
t.Hour(), t.Minute(), t.Second())