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https://github.com/twharmon/dynago

Simplify working with AWS DynamoDB.
https://github.com/twharmon/dynago

aws dynamodb go golang

Last synced: 14 days ago
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Simplify working with AWS DynamoDB.

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# Dynago

![](https://github.com/twharmon/dynago/workflows/Test/badge.svg) [![](https://goreportcard.com/badge/github.com/twharmon/dynago)](https://goreportcard.com/report/github.com/twharmon/dynago) [![codecov](https://codecov.io/gh/twharmon/dynago/branch/main/graph/badge.svg?token=K0P59TPRAL)](https://codecov.io/gh/twharmon/dynago)

The aim of this package is to make it easier to work with AWS DynamoDB.

## Documentation
For full documentation see [pkg.go.dev](https://pkg.go.dev/github.com/twharmon/dynago).

## Usage

### Basic
```go
package main

import (
"fmt"
"os"
"time"

"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/dynamodb"
"github.com/twharmon/dynago"
)

type Schema struct {}

func (s *Schema) PrimaryKeys() []string {
return []string{"PK", "SK"}
}

type Post struct {
// Embed a struct that implements the dynago.Keyer interface.
*Schema

// Set attribute name with `attr` tag if it needs to be different
// than field name. Use `fmt:"Post#{}"` to indicate how the value
// will be stored in DynamoDB.
ID string `attr:"PK" fmt:"Post#{}"`

Created time.Time `attr:"SK" fmt:"Created#{}"`
AuthorID string
Title string
Body string
}

func main() {
// Get client.
ddb := dynago.New(getDynamoDB(), &dynago.Config{
DefaultTableName: "tmp",
})

// Put item in DynamoDB.
p := Post{
ID: "hello-world",
Title: "Hi",
Body: "Hello world!",
Created: time.Now(),
}
if err := ddb.PutItem(&p).Exec(); err != nil {
panic(err)
}

// Get same item from DynamoDB. Fields used in the primary key
// must be set.
p2 := Post{
ID: p.ID,
Created: p.Created,
}
if err := ddb.GetItem(&p2).Exec(); err != nil {
panic(err)
}
fmt.Println(p2)
}

func getDynamoDB() *dynamodb.DynamoDB {
os.Setenv("AWS_SDK_LOAD_CONFIG", "true")
sess, err := session.NewSession()
if err != nil {
panic(err)
}
return dynamodb.New(sess)
}
```

### Additional Attributes
```go
package main

import (
"fmt"
"os"
"reflect"
"time"

"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/dynamodb"
"github.com/twharmon/dynago"
)

type Schema struct {}

func (s *Schema) PrimaryKeys() []string {
return []string{"PK", "SK"}
}

type Post struct {
// Embed a struct that implements the dynago.Keyer interface.
*Schema

ID string `attr:"PK" fmt:"Post#{}"`
AuthorID string
Title string
Body string
Created time.Time `attr:"SK" fmt:"Created#{}"`
}

type Author struct {
ID string `attr:"PK" fmt:"Author#{}"`

// Copy same value to attribute AltName by using `copy:"AltName"` in tag.
Name string `copy:"AltName"`
}

func main() {
// Get client.
ddb := dynago.New(getDynamoDB(), &dynago.Config{
DefaultTableName: "tmp",
AdditionalAttrs: additionalAttrs,
})

// ...
}

func additionalAttrs(item map[string]*dynamodb.AttributeValue, v reflect.Value) {
ty := v.Type().Name()

// Add a "Type" attribute to every item
item["Type"] = &dynamodb.AttributeValue{S: &ty}

// Add additional attributes for specific types
switch val := v.Interface().(type) {
case Author:
// Add a fat partition or sparse global secondary index to
// make querying for all authors possible
author := fmt.Sprintf("Author#%s", val.ID)
item["GSIPK"] = &dynamodb.AttributeValue{S: &ty}
item["GSISK"] = &dynamodb.AttributeValue{S: &author}
}
}
```

### Compound Field Attributes
```go
type Event struct {
Org string `attr:"PK" fmt:"Org#{}"`

// In this `fmt` tag, {} is equivalent to {Country}. You can
// reference a different field name by putting it's name in
// curly brackets.
Country string `attr:"SK" fmt:"Country#{}#City#{City}"`

// Since the City is specified in the "SK" attribute, we can
// skip putting it in another attribute if we want.
City string `attr:"-"`
Created time.Time
}
```

## Contribute
Make a pull request.