add go-pq code and result

* COMMENT -*- mode: org -*-

#+Date: 2016-12-16

Time-stamp: <2016-12-23>

Time-stamp: <2017-01-18>

* database binding benchmark

I want to know the efficiency of the db binding for different language,

--

0.50

28.0

** postgres 9.4, go 1.7.3, pq

0.385

27.0

--

0.367

27.6

--

0.423

30.7

--

0.362

27.2

--

0.372

26.4

* COMMENT -*- mode: org -*-

#+Date: 2017-01-18

Time-stamp: <2017-01-18>

* go, postgres, using lib/pq which is a pure go client

pq - GoDoc

https://godoc.org/github.com/lib/pq

SQLInterface · golang/go Wiki

https://github.com/golang/go/wiki/SQLInterface

database/sql is in stdlib.

Get dependency:

    go get github.com/lib/pq

To run it:

    go run bench.go

* dev

- problems

  - SELECT command failed: pq: SSL is not enabled on the server

    sslmode - Whether or not to use SSL (default is require, this is not the default for libpq)

    // stupid default param.

    https://www.postgresql.org/docs/9.1/static/libpq-ssl.html

    Table 31-1. SSL Mode Descriptions

    The default value for sslmode is prefer. Which is not supported by go's

    driver.

    I will use sslmode=disable for this benchmark.

  - panic: SELECT command failed: pq: remaining connection slots are reserved for non-replication superuser connections

    Does go create a new connection every time I run a query?

    type DB

    https://golang.org/pkg/database/sql/#DB

    You need to run Close() on the Rows, or call .Next() repeatedly until it

    closes itself.

    Common Pitfalls When Using database/sql in Go

    https://www.vividcortex.com/blog/2015/09/22/common-pitfalls-go/

package main

import (

	"fmt"

	"time"

	"log"

	"database/sql"

	_ "github.com/lib/pq"

)

const TIMES = 3000

func trackRunTime(start time.Time, name string) {

    elapsed := time.Since(start)

    log.Printf("%s took %s", name, elapsed)

}

func selectTest(db *sql.DB) {

	defer trackRunTime(time.Now(), "select")

	for i := 0; i < TIMES; i++ {

		rows, err := db.Query("SELECT id, bar FROM foo")

		if err != nil {

			panic(fmt.Sprintf("SELECT command failed: %v\n", err))

		}

		for rows.Next() {    // for used as while loop

			//fetch and ignore rows, this will also Close() the rows.

		}

	}

}

func updateTest(db *sql.DB) {

	defer trackRunTime(time.Now(), "update")

	for i := 0; i < TIMES; i++ {

		_, err := db.Exec("UPDATE foo SET bar=bar+1 WHERE id=1")

		if err != nil {

			panic(fmt.Sprintf("UPDATE command failed: %v\n", err))

		}

	}

}

func main() {

	db, err := sql.Open("postgres", "host=localhost dbname=t1 user=t1 password=fNfwREMqO69TB9YqE+/OzF5/k+s= sslmode=disable")

	if err != nil {

		log.Fatal(err)

	}

	selectTest(db)

	updateTest(db)

}