Getting a struct from PostGres DB - database

I followed a thread in here and came up with this
var b Button
queryErr := connection.QueryRow("SELECT id_printer, name, has_children FROM button WHERE id_parent IS NULL;").Scan(&b.ID, &b.Name, &b.Children)
if queryErr != nil {
response, err := json.MarshalIndent(b, "", " ")
fmt.Fprint(w, string(response))
if err != nil {
log.Println("Error on jsonmarshalindent Starter")
}
} else {
log.Println("Error on queryErr starter")
log.Println(queryErr)
fmt.Fprint(w, "Error getting starter button")
}
it has 2 problems:
It breaks on b.Children
I don't know how to make it dynamically. for instance, the query returns 3 rows, but it depends on the company's client, it can be 3 or any number.
the struct is
type Starter struct {
Buttons []Button `json:buttons`
}
type Button struct {
ID int `json:id`
Name string `json:name`
Children bool `json:children`
}
Can someone shed some light in this please?

For the bool, it depends on the type of the actual column. If it isn't boolean, it won't map directly.
You may need to store in a temporary variable first and then translate and assign to the field in Button to match.
As for reading all rows, here's an example adapted from the docs.
You use Query instead of QueryRow to get all rows.
rows, err := db.Query("SELECT id_printer, name, has_children FROM button WHERE id_parent IS NULL;")
if err != nil {
log.Fatal(err)
}
defer rows.Close()
var buttons []Button
for rows.Next() {
var b Button
if err := rows.Scan(&b.ID, &b.Name, &b.Children); err != nil {
log.Fatal(err)
}
buttons = append(buttons,b)
}
// At this point, you have all your rows in the "buttons" variable

Related

How can i mock database calls without a library?

i've been trying to wrap my head around unit testing, dependency injection, tdd and all that stuff and i've been stuck on testing functions that make database calls, for example.
Let's say you have a PostgresStore struct that takes in a Database interface, which has a Query() method.
type PostgresStore struct {
db Database
}
type Database interface {
Query(query string, args ...interface{}) (*sql.Rows, error)
}
And your PostgresStore has a GetPatients method, which calls database query.
func (p *PostgresStore) GetPatients() ([]Patient, error) {
rows, err := p.db.Query("SELECT id, name, age, insurance FROM patients")
if err != nil {
return nil, err
}
defer rows.Close()
items := []Patient{}
for rows.Next() {
var i Patient
if err := rows.Scan(
&i.ID,
&i.Name,
&i.Surname,
&i.Age,
&i.InsuranceCompany,
); err != nil {
return nil, err
}
items = append(items, i)
}
if err := rows.Close(); err != nil {
return nil, err
}
if err := rows.Err(); err != nil {
return nil, err
}
return items, nil
}
In the real implementation, you would just pass a *sql.DB as Database argument, but how would you guys write a unit test with a fake database struct?
let me try to clarify some of your doubts. First of all, I'm gonna share a working example to better understand what's going on. Then, I'm gonna mention all of the relevant aspects.
repo/db.go
package repo
import "database/sql"
type Patient struct {
ID int
Name string
Surname string
Age int
InsuranceCompany string
}
type PostgresStore struct {
// rely on the generic DB provided by the "sql" package
db *sql.DB
}
func (p *PostgresStore) GetPatient(id int) ([]Patient, error) {
rows, err := p.db.Query("SELECT id, name, age, insurance FROM patients")
if err != nil {
return nil, err
}
defer rows.Close()
items := []Patient{}
for rows.Next() {
var i Patient
if err := rows.Scan(
&i.ID,
&i.Name,
&i.Surname,
&i.Age,
&i.InsuranceCompany,
); err != nil {
return nil, err
}
items = append(items, i)
}
if err := rows.Close(); err != nil {
return nil, err
}
if err := rows.Err(); err != nil {
return nil, err
}
return items, nil
}
Here, the only relevant change is how you define the PostgresStore struct. As the db field, you should rely on the generic DB provided by the database/sql package of the Go Standard Library. Thanks to this, it's trivial to swap its implementation with a fake one, as we're gonna see later.
Please note that in the GetPatient method you're accepting an id parameter but you're not using it. Your query is more suitable to a method like GetAllPatients or something like that. Be sure to fix it accordingly.
repo/db_test.go
package repo
import (
"testing"
"github.com/DATA-DOG/go-sqlmock"
"github.com/stretchr/testify/assert"
)
func TestGetPatient(t *testing.T) {
// 1. set up fake db and mock
db, mock, err := sqlmock.New()
if err != nil {
t.Fatalf("err not expected: %v", err)
}
// 2. configure the mock. What we expect (query or command)? The outcome (error vs no error).
rows := sqlmock.NewRows([]string{"id", "name", "surname", "age", "insurance"}).AddRow(1, "john", "doe", 23, "insurance-test")
mock.ExpectQuery("SELECT id, name, age, insurance FROM patients").WillReturnRows(rows)
// 3. instantiate the PostgresStore with the fake db
sut := &PostgresStore{
db: db,
}
// 4. invoke the action we've to test
got, err := sut.GetPatient(1)
// 5. assert the result
assert.Nil(t, err)
assert.Contains(t, got, Patient{1, "john", "doe", 23, "insurance-test"})
}
Here, there are a lot to cover. First, you can check the comments within the code that give you a better idea of each step. In the code, we're relying on the package github.com/DATA-DOG/go-sqlmock that allows us to easily mock a database client.
Obviously, the purpose of this code is to give a general idea on how to implement your needs. It can be written in a better way but it can be a good starting point for writing tests in this scenario.
Let me know if this helps, thanks!

Can't PUT GridDB Containers using the go_client

I'm trying to PUT my GridDB container (a simple container for users on my website) but it's having issues.
I've confirmed that the sample code for the go_client works so it's not an issue of improper build or anything of that sort.
func getAdminUsers(c echo.Context) error {
var tmp []interface{}
col, err1 := gridstore.GetContainer("users")
if err1 != nil {
fmt.Println("get container failed")
}
col.SetAutoCommit(true)
// Create normal query
query, err := col.Query("SELECT *")
if err != nil {
fmt.Println("create query failed")
}
//Execute query
rs, err := query.Fetch(true)
if err != nil {
fmt.Println("create rs from query failed")
}
for rs.HasNext() {
// Update row
rrow, err := rs.NextRow()
if err != nil {
fmt.Println("NextRow from rs failed")
}
tmp = rrow
fmt.Println("Person: name=", rrow[0], " status=", rrow[1], " count=", rrow[2], " lob=", rrow[3])
}
col.Commit()
fmt.Println(tmp)
return c.Render(http.StatusOK, "admin", "admin")
}
My container is properly being written but for some reason the querying isn't working. This is rather basic code so I expect there's some minor detail I'm missing somewhere.
As of now, I'm getting errors here: "get container failed". My error could either be from writing or querying, though I suspect it's from querying.
Can you try initializing your container by using the CreateContainerInfo instead? It will create container if it doesn't exist, but if it does exist, it's a more robust method of calling your container.
conInfo, _ := griddb_go.CreateContainerInfo("Users",
[][]interface{}{
{"email", griddb_go.TYPE_STRING},
{"password", griddb_go.TYPE_BLOB}},
griddb_go.CONTAINER_COLLECTION,
true)
col, _ := gridstore.PutContainer(conInfo, false)

How to make scanning DB rows in Go DRY?

I have a table in the database containing user account information. I have a struct called User defined.
type User struct {
Id uint
Username string
Password string
FirstName string
LastName string
Address1 string
Address2 string
.... a bunch more fields ...
}
For fetching individual user accounts, I have a method defined
func (user *User) GetById(db *sql.DB, id uint) error {
query := `SELECT
...a whole bunch of SQL ...
WHERE id = $1
... more SQL ...
LIMIT 1`
row := db.QueryRow(query, id)
err := row.Scan(
&user.Id,
&user.UserName,
&user.Password,
&user.FirstName,
&user.LastName,
... some 20 more lines of fields read into the struct ...
)
if err != nil {
return err
}
return nil
}
And there are several places in the system where I need to fetch user information as part of a larger query. That is, I am fetching some other type of object, but also a user account related to it.
That means, I have to repeat the whole rows.Scan(&user.Username, &user...) thing over and over again and it takes a whole page and it is error prone and if I ever change the user table structure I would have to change the code in a whole bunch of places. How can I make this more DRY?
Edit: I am not sure why this was marked as a duplicate, but since this edit is required, I will try to explain one more time. I am not asking how to scan a row into a struct. I already know how to do that, as the code above clearly shows. I am asking how to structure the struct scanning code in such a way that I do not have to repeat the same page of scanning code every time I am scanning the same type of struct.
Edit: also, yes, I am aware of sqlstruct and sqlx and similar libraries. I am deliberately avoiding these, because they depend on reflect package with well documented performance issues. And I intend to potentially scan millions of rows using these techniques (not millions of users, but this question extends to other record types).
Edit: so, yes, I know I should write a function. I am not sure what this function should take as arguments and what results it should return. Lets say that the other query I want to accommodate looks like this
SELECT
s.id,
s.name,
... more site fields ...
u.id,
u.username,
... more user fields ...
FROM site AS s
JOIN user AS u ON (u.id = s.user_id)
JOIN some_other_table AS st1 ON (site.id = st1.site_id)
... more SQL ...
And I have a site struct method that embeds a user struct. I don't want to repeat the user scanning code here. I want to call a function that will scan the user portion of the raw into a user struct the same way it does in the user method above.
To eliminate the repetition of the required steps to scan the *sql.Rows structure you could introduce two interfaces. One that describes the already implemented behaviour of *sql.Rows and *sql.Row.
// This interface is already implemented by *sql.Rows and *sql.Row.
type Row interface {
Scan(...interface{}) error
}
And another one that abstracts away the actual scanning step of the row(s).
// have your entity types implement this one
type RowScanner interface {
ScanRow(Row) error
}
An example implementation of the RowScanner interface could look like this:
type User struct {
Id uint
Username string
// ...
}
// Implements RowScanner
func (u *User) ScanRow(r Row) error {
return r.Scan(
&u.Id,
&u.Username,
// ...
)
}
type UserList struct {
Items []*User
}
// Implements RowScanner
func (list *UserList) ScanRow(r Row) error {
u := new(User)
if err := u.ScanRow(r); err != nil {
return err
}
list.Items = append(list.Items, u)
return nil
}
With these interfaces you can now dry your rows-scanning code for all of your types that implement the RowScanner interface by using these two functions.
func queryRows(query string, rs RowScanner, params ...interface{}) error {
rows, err := db.Query(query, params...)
if err != nil {
return err
}
defer rows.Close()
for rows.Next() {
if err := rs.ScanRow(rows); err != nil {
return err
}
}
return rows.Err()
}
func queryRow(query string, rs RowScanner, params ...interface{}) error {
return rs.ScanRow(db.QueryRow(query, params...))
}
// example
ulist := new(UserList)
if err := queryRows(queryString, ulist, arg1, arg2); err != nil {
panic(err)
}
// or
u := new(User)
if err := queryRow(queryString, u, arg1, arg2); err != nil {
panic(err)
}
If you have composite types that you want to scan but you want to avoid having to repeat the enumeration of its elements' fields, then you could introduce a method that returns a type's fields and reuse that method where you need it. For example:
func (u *User) ScannableFields() []interface{} {
return []interface{}{
&u.Id,
&u.Username,
// ...
}
}
func (u *User) ScanRow(r Row) error {
return r.Scan(u.ScannableFields()...)
}
// your other entity type
type Site struct {
Id uint
Name string
// ...
}
func (s *Site) ScannableFields() []interface{} {
return []interface{}{
&p.Id,
&p.Name,
// ...
}
}
// Implements RowScanner
func (s *Site) ScanRow(r Row) error {
return r.Scan(s.ScannableFields()...)
}
// your composite
type UserWithSite struct {
User *User
Site *Site
}
// Implements RowScanner
func (u *UserWithSite) ScanRow(r Row) error {
u.User = new(User)
u.Site = new(Site)
fields := append(u.User.ScannableFields(), u.Site.ScannableFields()...)
return r.Scan(fields...)
}
// retrieve from db
u := new(UserWithSite)
if err := queryRow(queryString, u, arg1, arg2); err != nil {
panic(err)
}

Golang graphql iterate over map with submap

Recently I was trying to an implementation of a Mutation Request using GoLang as a Graphql Server, Basically this is the query that i send: As you can see its an array of object that contains name and an array of strings
mutation{
CellTest(cells:[{name:"lero",child:["1","2"]},{name:"lero2",child:["12","22"]}]){
querybody
}
}
In my Go code I have a type object that is gonna set the values sent
type Cell struct {
name string `json:"name"`
child []string `json:"child"`
}
and a custom array that is gonna be []Cell
type Cells []*Cell
However when the request is received by GO I get this:
Note that this is the print of cellsInterface
[map[child:[1 2] name:lero] map[child:[12 22] name:lero2]]
How can i get each value and assign those in my Array Cells
something like this:
Cells[0] = {name="first",child={"1","2"}}
Cells[1] = {name="second",child={"hello","good"}}
this is my current attempt:
var resolvedCells Cells
cellsInterface := params.Args["cells"].([]interface{})
cellsByte, err := json.Marshal(cellsInterface)
if err != nil {
fmt.Println("marshal the input json", err)
return resolvedCells, err
}
if err := json.Unmarshal(cellsByte, &resolvedCells); err != nil {
fmt.Println("unmarshal the input json to Data.Cells", err)
return resolvedCells, err
}
for cell := range resolvedCells {
fmt.Println(cellsInterface[cell].([]interface{}))
}
However this only split the cells array into 0 and 1.
Range through the map values in the result and append those values to Cell slice. If you are getting an object from json. Then you can unmarshall the bytes into Cell.
The result when unmarshalling should be a slice of Cell struct as
var resolvedCells []Cell
if err := json.Unmarshal(cellsByte, &resolvedCells); err != nil {
fmt.Println("unmarshal the input json to Data.Cells", err)
}
fmt.Println(resolvedCells)
Working Code on Go playground
Or if you want to use pointers loop over the resolvedCell as
type Cells []*Cell
func main() {
var resolvedCells Cells
if err := json.Unmarshal(cellsByte, &resolvedCells); err != nil {
fmt.Println("unmarshal the input json to Data.Cells", err)
}
fmt.Println(*resolvedCells[1])
for _, value := range resolvedCells{
fmt.Println(value)
fmt.Printf("%+v",value.Child) // access child struct value of array
}
}
Playground example

How to query a entity from datastore with Namespace In golang?

I am working on a multi tenant application, I need to query a particular user from a KIND and From Particular Namespace.
I am able to get the values from default Namespace.the package i am using here is "google.golang.org/appengine/datastore"
q := datastore.NewQuery(ENTITYNAME).Filter("Name =", ed.Expense.Name)
var expenses []ExpenseEntiry
return q.GetAll(ed.Ctx, &expenses)
The namespace value is not part of the query (it's not a property of the query). The namespace comes from the context which you pass when executing the query, e.g. to Query.GetAll().
If you have a context (you do as you pass it to q.GetAll()), you can create a derivative context with a given namespace using the appengine.Namespace() function.
For example:
ctx2, err := appengine.Namespace(ed.Ctx, "mynamespace")
// check err
And use this new context to pass to Query.GetAll():
return q.GetAll(ctx2, &expenses)
It is rare that you need to create a new context with a different namespace, ed.Ctx should already be a context with the right namespace. So when / where you create ed.Ctx, you should already apply the namespace there, so you can avoid "accidental" exposure of data of other tenants (which is a major security issue).
If you are using the old lib: google.golang.org/appengine/datastore, then you need to create the context with the namespace:
ctx2, err := appengine.Namespace(ed.Ctx, "mynamespace")
if err != nil {
return err
}
But you WANT to be using the latest lib: cloud.google.com/go/datastore. The Namespace can be set directly on the Query object. This is new. You must then run the query using datastoreClient.Run(ctx, query).
func deleteTestNamespace(ctx context.Context, namespaces string) error {
dsClient, err := datastore.NewClient(ctx, log, datastore.Config{...})
err := dsClient.DeleteMulti(ctx, keys[i:i+chunk])
if err != nil {
return err
}
var keys []*datastore.Key
for _, kind := range envKinds {
// Get all keys
query := datastore.NewQuery(kind).KeysOnly().Namespace(namespace)
it := dsClient.Run(ctx, query)
for {
var key datastore.Key
_, err := it.Next(&key)
if err == iterator.Done {
break
}
if err != nil {
return err
}
keys = append(keys, &key)
}
// Delete all records in chunks of 500 or less
for i := 0; i < len(keys); i += 500 {
chunk := min(len(keys)-i, 500)
err := dsClient.DeleteMulti(ctx, keys[i:i+chunk])
if err != nil {
return err
}
}
}
return nil
}
func min(num1 int, num2 int) int {
if num1 < num2 {
return num1
}
return num2
}

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