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dynamodb.go
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dynamodb.go
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package mawsgo
import (
"fmt"
"strconv"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/dynamodb"
"github.com/aws/aws-sdk-go/service/dynamodb/dynamodbattribute"
"github.com/aws/aws-sdk-go/service/dynamodb/expression"
)
// ---------------------------------------------------------------------------
// Abstrakce nad DynamoDB tabulkou. Zjednodusene schema tabulky, kde
// existuje pouze jeden primarni klic (KeyItem) typu string (typicky UUID)
// ---------------------------------------------------------------------------
// Predpokladame jiz existenci tabulky (zrizene v AWS)
type MAWSDynamoTable struct {
// jmeno tabulky
TableName string
// jeden key atribut typu string !!!
KeyItem string
// handle na tabulku
Handle *dynamodb.DynamoDB
// handle na spojeni AWS (kopiruje se)
AWS *session.Session
}
// ---------------------------------------------------------------------------
// vytvoreni Handle na Dynamo DB tabulku splnujici schema
func (maws *MAWS) MAWSMakeDynamoTable(name string, keyItem string) *MAWSDynamoTable {
//
return &MAWSDynamoTable{
TableName: name,
KeyItem: keyItem,
Handle: dynamodb.New(maws.AWS),
AWS: maws.AWS,
}
}
// ---------------------------------------------------------------------------
// vlozeni v zasade libovolneho typu struct do tabulky
func (tbl *MAWSDynamoTable) PutItem(itm interface{}) error {
// konverze obsahu na mapu klic-hodnota
_item, _err := dynamodbattribute.MarshalMap(itm)
//
if _err != nil {
//
return _err
}
// put
_, __err := tbl.Handle.PutItem(&dynamodb.PutItemInput{
Item: _item,
TableName: aws.String(tbl.TableName)})
// je ok?
return __err
}
// ---------------------------------------------------------------------------
// getitem, opet velmi dynamicky-volna typova kontrola
func (tbl *MAWSDynamoTable) GetItem(keyValue string, itm interface{}) error {
//
_get, _err := tbl.Handle.GetItem(&dynamodb.GetItemInput{
TableName: aws.String(tbl.TableName),
Key: DynamoDBStringKey(tbl.KeyItem, keyValue),
})
// neco neni oukej
if _get.Item == nil || _err != nil {
//
return _err
}
// oukeja
return dynamodbattribute.UnmarshalMap(_get.Item, &itm)
}
// ---------------------------------------------------------------------------
// deleteitem, key
func (tbl *MAWSDynamoTable) DeleteItem(keyValue string) error {
//
_, _err := tbl.Handle.DeleteItem(&dynamodb.DeleteItemInput{
TableName: aws.String(tbl.TableName),
Key: DynamoDBStringKey(tbl.KeyItem, keyValue),
})
// oukeja
return _err
}
// ---------------------------------------------------------------------------
// keyValue - primarni klic zaznamu
// updateCmd - syntax odpovida pozadavkum AWS
// -- set COSI = :arg, COSIJ = :argj, ...
// args - key:value
func (tbl *MAWSDynamoTable) UpdateItem(keyValue string, updateCmd string, args map[string]interface{}) error {
//
input := &dynamodb.UpdateItemInput{
ExpressionAttributeValues: DynamoDBKeys(args),
TableName: aws.String(tbl.TableName),
Key: DynamoDBStringKey(tbl.KeyItem, keyValue),
ReturnValues: aws.String("UPDATED_NEW"),
UpdateExpression: aws.String(updateCmd),
}
_, err := tbl.Handle.UpdateItem(input)
//
return err
}
// ---------------------------------------------------------------------------
// ValRecord - musi byt pole/slice !!!
// ---------------------------------------------------------------------------
// cond - filtracni condition
// LessThan, GreaterThan, Equal, *Equal
// filt := expression.Name("Age").GreaterThan(expression.Value(10))
func (tbl *MAWSDynamoTable) Scan(cond expression.ConditionBuilder, ValRecord interface{}) error {
// vytvoreni zaznamu o filtru
expr, _exprerr := expression.NewBuilder().WithFilter(cond).Build()
//
if _exprerr != nil {
//
return _exprerr
}
// parametry scanu
params := &dynamodb.ScanInput{
ExpressionAttributeNames: expr.Names(),
ExpressionAttributeValues: expr.Values(),
FilterExpression: expr.Filter(),
ProjectionExpression: expr.Projection(),
TableName: aws.String(tbl.TableName),
}
//
res, scanerr := tbl.Handle.Scan(params)
//
if res.Items == nil || scanerr != nil {
//
return scanerr
}
//
return dynamodbattribute.UnmarshalListOfMaps(res.Items, ValRecord)
}
// ---------------------------------------------------------------------------
//
func DynamoDBStringKey(key, value string) map[string]*dynamodb.AttributeValue {
//
return map[string]*dynamodb.AttributeValue{
key: {
S: aws.String(value),
},
}
}
// ---------------------------------------------------------------------------
//
func DynamoDBNumKey(key string, value int) map[string]*dynamodb.AttributeValue {
//
_val := strconv.Itoa(value)
//
return map[string]*dynamodb.AttributeValue{
key: {
N: aws.String(_val),
},
}
}
// ---------------------------------------------------------------------------
//
func DynamoDBKeys(asmap map[string]interface{}) map[string]*dynamodb.AttributeValue {
//
_val := make(map[string]*dynamodb.AttributeValue)
//
for k, v := range asmap {
//
switch tp := v.(type) {
case int:
_val[k] = &dynamodb.AttributeValue{N: aws.String(strconv.Itoa(tp))}
case float64:
_tp := fmt.Sprintf("%f", tp)
_val[k] = &dynamodb.AttributeValue{N: aws.String(_tp)}
case string:
_val[k] = &dynamodb.AttributeValue{S: aws.String(tp)}
default:
panic("neznam typ")
}
}
//
return _val
}