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scan_items.go
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scan_items.go
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// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
package main
import (
"fmt"
"log"
"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"
)
// Create structs to hold info about new item
type ItemInfo struct {
Plot string `json:"plot"`
Rating float64 `json:"rating"`
}
type Item struct {
Year int `json:"year"`
Title string `json:"title"`
Info ItemInfo `json:"info"`
}
// Get the movies with a minimum rating of 8.0 in 2011
func main() {
min_rating := 8.0
year := 2011
// Initialize a session in us-west-2 that the SDK will use to load
// credentials from the shared credentials file ~/.aws/credentials.
sess, err := session.NewSession(&aws.Config{
Region: aws.String("us-west-2")},
)
if err != nil {
log.Fatalf("Got error creating session: %s", err)
}
// Create DynamoDB client
svc := dynamodb.New(sess)
// Create the Expression to fill the input struct with.
// Get all movies in that year; we'll pull out those with a higher rating later
filt := expression.Name("year").Equal(expression.Value(year))
// Or we could get by ratings and pull out those with the right year later
// filt := expression.Name("info.rating").GreaterThan(expression.Value(min_rating))
// Get back the title, year, and rating
proj := expression.NamesList(expression.Name("title"), expression.Name("year"), expression.Name("info.rating"))
expr, err := expression.NewBuilder().WithFilter(filt).WithProjection(proj).Build()
if err != nil {
log.Fatalf("Got error building expression: %s", err)
}
// Build the query input parameters
params := &dynamodb.ScanInput{
ExpressionAttributeNames: expr.Names(),
ExpressionAttributeValues: expr.Values(),
FilterExpression: expr.Filter(),
ProjectionExpression: expr.Projection(),
TableName: aws.String("Movies"),
}
// Make the DynamoDB Query API call
result, err := svc.Scan(params)
if err != nil {
log.Fatalf("Query API call failed: %s", err)
}
num_items := 0
for _, i := range result.Items {
item := Item{}
err = dynamodbattribute.UnmarshalMap(i, &item)
if err != nil {
log.Fatalf("Got error unmarshalling: %s", err)
}
// Which ones had a higher rating?
if item.Info.Rating > min_rating {
// Or it we had filtered by rating previously:
// if item.Year == year {
num_items += 1
fmt.Println("Title: ", item.Title)
fmt.Println("Rating:", item.Info.Rating)
fmt.Println()
}
}
fmt.Println("Found", num_items, "movie(s) with a rating above", min_rating, "in", year)
}