[20 Days of DynamoDB] Day 4 - Conditional UpdateItem

Posted: 11/Jan/2024

Conditional operations are helpful in cases when you want a DynamoDB write operation (PutItem, UpdateItem or DeleteItem) to be executed based on a certain criteria. To do so, use a condition expression - it must evaluate to true in order for the operation to succeed.

Here is an example that demonstrates a conditional UpdateItem operation. It uses the attribute_not_exists function:

    resp, err := client.UpdateItem(context.Background(), &dynamodb.UpdateItemInput{
        TableName: aws.String(tableName),
        Key: map[string]types.AttributeValue{
            "email": &types.AttributeValueMemberS{Value: email},
        },
        UpdateExpression: aws.String("SET first_name = :fn"),
        ExpressionAttributeValues: map[string]types.AttributeValue{
            ":fn": &types.AttributeValueMemberS{
                Value: firstName,
            },
        },

        ConditionExpression:    aws.String("attribute_not_exists(account_locked)"),
        ReturnConsumedCapacity: types.ReturnConsumedCapacityTotal,
    })

Recommended reading - ConditionExpressions