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scan_items.go

Gets items from and Amazon DymanoDB table using the Expression Builder package.

/* Copyright 2010-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved. This file is licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance with the License. A copy of the License is located at http://aws.amazon.com/apache2.0/ This file is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. */ package main import ( "fmt" "os" "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 { fmt.Println("Got error creating session:") fmt.Println(err.Error()) os.Exit(1) } // 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 { fmt.Println("Got error building expression:") fmt.Println(err.Error()) os.Exit(1) } // 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 { fmt.Println("Query API call failed:") fmt.Println((err.Error())) os.Exit(1) } num_items := 0 for _, i := range result.Items { item := Item{} err = dynamodbattribute.UnmarshalMap(i, &item) if err != nil { fmt.Println("Got error unmarshalling:") fmt.Println(err.Error()) os.Exit(1) } // 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) }

Sample Details

Service: dynamodb

Last tested: 2018-03-16

Author: Doug-AWS

Type: full-example

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