Created
April 22, 2015 02:29
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golang db scan comparison
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package main | |
import ( | |
"database/sql" | |
"encoding/json" | |
"fmt" | |
_ "github.com/mattn/go-sqlite3" | |
) | |
func getDB() *sql.DB { | |
db, _ := sql.Open("sqlite3", ":memory:") | |
if _, err := db.Exec("CREATE TABLE test (id INT NOT NULL, name VARCHAR(255))"); err != nil { | |
panic(err) | |
} | |
if _, err := db.Exec("INSERT INTO test (id, name) VALUES (123, null),(456,'bob')"); err != nil { | |
panic(err) | |
} | |
return db | |
} | |
type user struct { | |
Id int `json:"id"` | |
Name string `json:"name"` | |
} | |
type userNPtr struct { | |
Id int `json:"id"` | |
Name *string `json:"name"` | |
} | |
type userNEmpty struct { | |
Id int `json:"id"` | |
Name string `json:"name,omitempty"` | |
} | |
type userNPtrEmpty struct { | |
Id int `json:"id"` | |
Name *string `json:"name,omitempty"` | |
} | |
func main() { | |
db := getDB() | |
scanners := []struct { | |
name string | |
f func(*sql.Rows) (string, []byte) | |
}{ | |
{"scanUser", scanUser}, | |
{"scanUser_ptr", scanUser_ptr}, | |
{"scanUserNPtr", scanUserNPtr}, | |
{"scanUserNEmpty", scanUserNEmpty}, | |
{"scanUserNEmpty_ptr", scanUserNEmpty_ptr}, | |
{"scanUserNPtrEmpty", scanUserNPtrEmpty}, | |
} | |
rows, err := db.Query("SELECT id,name FROM test") | |
if err != nil { | |
panic(err) | |
} | |
defer rows.Close() | |
for rows.Next() { | |
for _, scanner := range scanners { | |
printfv, jsonb := scanner.f(rows) | |
fmt.Printf("%-20s %-30s %s\n", scanner.name, printfv, jsonb) | |
} | |
} | |
} | |
func scanUser(rows *sql.Rows) (string, []byte) { | |
var u user | |
var name sql.NullString | |
rows.Scan(&u.Id, &name) | |
if name.Valid { | |
u.Name = name.String | |
} | |
jsonString, _ := json.Marshal(u) | |
return fmt.Sprintf("%+v", u), jsonString | |
} | |
func scanUser_ptr(rows *sql.Rows) (string, []byte) { | |
var u user | |
var name *string | |
rows.Scan(&u.Id, &name) | |
if name != nil { | |
u.Name = *name | |
} | |
jsonString, _ := json.Marshal(u) | |
return fmt.Sprintf("%+v", u), jsonString | |
} | |
func scanUserNPtr(rows *sql.Rows) (string, []byte) { | |
var u userNPtr | |
rows.Scan(&u.Id, &u.Name) | |
jsonString, _ := json.Marshal(u) | |
return fmt.Sprintf("%+v", u), jsonString | |
} | |
func scanUserNEmpty(rows *sql.Rows) (string, []byte) { | |
var u userNEmpty | |
var name sql.NullString | |
rows.Scan(&u.Id, &name) | |
if name.Valid { | |
u.Name = name.String | |
} | |
jsonString, _ := json.Marshal(u) | |
return fmt.Sprintf("%+v", u), jsonString | |
} | |
func scanUserNEmpty_ptr(rows *sql.Rows) (string, []byte) { | |
var u userNEmpty | |
var name *string | |
rows.Scan(&u.Id, &name) | |
if name != nil { | |
u.Name = *name | |
} | |
jsonString, _ := json.Marshal(u) | |
return fmt.Sprintf("%+v", u), jsonString | |
} | |
func scanUserNPtrEmpty(rows *sql.Rows) (string, []byte) { | |
var u userNPtrEmpty | |
rows.Scan(&u.Id, &u.Name) | |
jsonString, _ := json.Marshal(u) | |
return fmt.Sprintf("%+v", u), jsonString | |
} |
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# go run main.go | |
scanUser {Id:123 Name:} {"id":123,"name":""} | |
scanUser_ptr {Id:123 Name:} {"id":123,"name":""} | |
scanUserNPtr {Id:123 Name:<nil>} {"id":123,"name":null} | |
scanUserNEmpty {Id:123 Name:} {"id":123} | |
scanUserNEmpty_ptr {Id:123 Name:} {"id":123} | |
scanUserNPtrEmpty {Id:123 Name:<nil>} {"id":123} | |
scanUser {Id:456 Name:bob} {"id":456,"name":"bob"} | |
scanUser_ptr {Id:456 Name:bob} {"id":456,"name":"bob"} | |
scanUserNPtr {Id:456 Name:0xc20800a850} {"id":456,"name":"bob"} | |
scanUserNEmpty {Id:456 Name:bob} {"id":456,"name":"bob"} | |
scanUserNEmpty_ptr {Id:456 Name:bob} {"id":456,"name":"bob"} | |
scanUserNPtrEmpty {Id:456 Name:0xc20800a980} {"id":456,"name":"bob"} |
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