database.go

package main

import (
	"database/sql"
	"fmt"

	"github.com/lib/pq"
)

type DatabaseInfo struct {
	Username string
	Password string
	Host     string
	DbName   string
}

type Data struct {
	Col1 string
	Col2 string
	Col3 string
}

func bulk_insert(db *sql.DB, data []Data) error {
	transaction, err := db.Begin()
	if err != nil {
		fmt.Println(err)
		return err
	}

	statement, err := transaction.Prepare(pq.CopyIn("tablename", "col1", "col2", "col3"))
	if err != nil {
		fmt.Println(err)
		return err
	}

	for _, d := range data {
		_, err = statement.Exec(d.Col1, d.Col2, d.Col3)
		if err != nil {
			fmt.Println(err)
			return err
		}
	}

	if err = statement.Close(); err != nil {
		fmt.Println(err)
		return err
	}

	if err = transaction.Commit(); err != nil {
		fmt.Println(err)
		return err
	}
}

func query_for_multiple_rows(db *sql.DB, query string) ([]Data, error) {
	var datas []Data
	rows, err := db.Query(query)
	if err != nil {
		fmt.Println(err)
		return datas, err
	}

	defer rows.Close()

	for rows.Next() {
		var d Data
		if err = rows.Scan(&d.Col1, &d.Col2, &d.Col3); err != nil {
			fmt.Println(err)
		} else {
			datas = append(datas, d)
		}
	}

	return datas, nil
}

func query_for_single_row(db *sql.DB, query string, id int) (Data, error) {
	var data Data
	if err := database.QueryRow(query, id).Scan(&d.Col1, &d.Col2, &d.Col3); err != nil {
		fmt.Println(err)
		return Data{}, err
	}

	return data, nil
}

func main() {
	var dbInfo DatabaseInfo

	//Fill out dbInfo before this call
	dbURL := fmt.Sprintf("postgres://%s:%s@%s/%s", dbInfo.Username, dbInfo.Password, dbInfo.Host, dbInfo.DbName)
	db, err := sql.Open("postgres", dbURL)
	if err != nil {
		fmt.Println(err)
		return
	}

	//Both db.Query and db.QueryRow take variable amount of arguments
	//	the first being the SQL string and the rest the variables
	//	that are being passed to the query
	fmt.Println(query_for_multiple_rows(db, "select * from data"))
	fmt.Println(query_for_single_row(db, "select * from data where id = $1", 1))
}