Join several time-series from influxdb to a single csv output.

influx_to_csv.go

package main

import (
	"fmt"
	"log"
	"github.com/influxdata/influxdb/client/v2"
	"strings"
	"flag"
)

func main() {

	database := flag.String("database", "forecasts", "specify database name")
	username := flag.String("username", "admin", "specify database user")
	password := flag.String("password", "password", "specify user password")
	hostname := flag.String("hostname", "http://localhost:8086", "specify database hostname")
	query := flag.String("query", "select * from oslo, trondheim, stavanger", "query to execute")

	flag.Parse()

	// Create a new HTTPClient
	c, err := client.NewHTTPClient(client.HTTPConfig{
		Addr:               *hostname,
		Username:           *username,
		Password:           *password,
		InsecureSkipVerify: true,
	})

	if err != nil {
		log.Fatal(err)
	}

	res, err := queryDB(c, *database, *query)
	if err != nil {
		log.Fatal(err)
	}

	// headers
	for _, r := range res {
		var colNames []string
		for _, series := range r.Series {
			colNames = append(colNames, series.Columns...)
		}
		fmt.Println(strings.Join(colNames, ", "))
	}

	// join all values
	allValues := make(map[interface{}][]interface{})
	allTimes := make([]interface{}, 0)
	for _, r := range res {
		for _, series := range r.Series {
			for rowNumber, rowValues := range series.Values {
				if _, exists := allValues[rowValues[0]]; exists {
					allValues[rowValues[0]] = append(allValues[rowValues[0]], rowValues[1:]...)
				} else {
					allTimes = append(allTimes, rowValues[0])
					allValues[rowValues[0]] = rowValues
				}
			}
		}
	}

	// print results
	for _, time := range allTimes {
		fmt.Println(join(allValues[time], ","))
	}

}

// join values to a comma-separated string
func join(values []interface{}, sep string) (string) {
	ss := make([]string, len(values))
	for k, v := range values {
		ss[k] = fmt.Sprintf("%v", v)
	}
	return strings.Join(ss, sep)
}

func queryDB(clnt client.Client, database, cmd string) (res []client.Result, err error) {
	q := client.Query{
		Command:  cmd,
		Database: database,
	}
	if response, err := clnt.Query(q); err == nil {
		if response.Error() != nil {
			return res, response.Error()
		}
		res = response.Results
	} else {
		return res, err
	}
	return res, nil
}