CODEWITHSUNDEEP
goamazon-dynamodb
j3d
j3d

Reputation: 9724

How to Delete Multiple Items from a DynamoDB Table in Go

I've a DynamoDB table that contains items like this:

type AuthEntry struct {
    UserID    string    `dynamodbav:"userId"`
    Token     string    `dynamodbav:"token"`
    CreatedOn time.Time `dynamodbav:"createdOn"`
}

I need to delete all the AuthEntry items older than 5 minutes (CreatedOn < now - 5 mins) and without a token (Token is empty). It is clear to me how to remove one item at a time... but I'm wondering how to delete multiple items in one shot. Thank u very much.

Upvotes: 1

Views: 6430

Answers (2)

j3d
j3d

Reputation: 9724

I was looking for an example like the one here below... and I hope it helps other newbie like me. For instance, first I use Scan to retrieve the expired entries, and then I run BatchWriteItemInput to actually delete them.

import (
    "context"
    "time"

    "github.com/aws/aws-sdk-go-v2/aws"
    "github.com/aws/aws-sdk-go-v2/config"
    "github.com/aws/aws-sdk-go-v2/feature/dynamodb/attributevalue"
    "github.com/aws/aws-sdk-go-v2/service/dynamodb"
    "github.com/aws/aws-sdk-go-v2/service/dynamodb/types"

)

var tableName = "USER_AUTH"

...

type AuthRepository struct {
    ctx context.Context
    svc *dynamodb.Client
}

...

func NewAuthRepository(ctx context.Context) (*AuthRepository, error) {
    cfg, err := config.LoadDefaultConfig(ctx)
    if err != nil {
        return nil, err
    }

    return &AuthRepository{ctx, dynamodb.NewFromConfig(cfg)}, nil
}

...

func (r *AuthRepository) Collect(maxAge int) (int32, error) {
    t := time.Now().Add(time.Duration(maxAge*-1) * time.Millisecond).UTC()
    params := &dynamodb.ScanInput{
        TableName:            aws.String(tableName),
        ProjectionExpression: aws.String("userId"),
        ExpressionAttributeValues: map[string]types.AttributeValue{
            "t": &types.AttributeValueMemberS{*aws.String(t.String())},
        },
        FilterExpression: aws.String("createdOn < :t"),
    }

    result, err := r.svc.Scan(r.ctx, params)
    if err != nil {
        return 0, err
    }

    wr := make([]types.WriteRequest, result.Count)
    for _, v := range result.Items {
        authEntry := &AuthEntry{}
        if err := attributevalue.UnmarshalMap(v, &authEntry); err != nil {
        return 0, err
        }
        wr = append(wr, types.WriteRequest{
            DeleteRequest: &types.DeleteRequest{
                Key: map[string]types.AttributeValue{
                    "userId": &types.AttributeValueMemberS{*aws.String(authEntry.UserID)},
                },
            }})
    }

    input := &dynamodb.BatchWriteItemInput{
        RequestItems: map[string][]types.WriteRequest{
            tableName: wr,
        },
    }

    _, err = r.svc.BatchWriteItem(r.ctx, input)
    return result.Count, nil
}

Upvotes: 4

Seth Geoghegan
Seth Geoghegan

Reputation: 5747

When it comes to deletion, you have a few options.

deleteItem - Deletes a single item in a table by primary key.

batchWriteItem - The BatchWriteItem operation puts or deletes multiple items in one or more tables. A single call to BatchWriteItem can write up to 16 MB of data, which can comprise as many as 25 put or delete requests

TimeToLive - You can utilize DynamoDBs Time To Live (TTL) feature to delete items you no longer need. Keep in mind that TTL only marks your items for deletion and actual deletion could take up to 48 hours.

I'm not sure which items in your table are part of the primary key, so it's difficult to give you an example. However, this operation is the preferred method to delete multiple items at a time.

Upvotes: 4

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