You are previewing Programming Amazon Web Services.

Programming Amazon Web Services

Cover of Programming Amazon Web Services by James Murty Published by O'Reilly Media, Inc.
  1. Programming Amazon Web Services
    1. SPECIAL OFFER: Upgrade this ebook with O’Reilly
    2. A Note Regarding Supplemental Files
    3. Preface
      1. What’s in This Book?
      2. Ruby and Interactive Examples
      3. Conventions Used in This Book
      4. Using Code Examples
      5. Safari® Enabled
      6. How to Contact Us
      7. Acknowledgments
    4. 1. Infrastructure in the Cloud
      1. Amazon Web Services for Infrastructure
      2. Thinking Like Amazon
      3. Reality Check
      4. Interfaces: REST and Query Versus SOAP
    5. 2. Interacting with Amazon Web Services
      1. REST-Based APIs
      2. User Authentication
      3. Performing AWS Requests
    6. 3. S3: Simple Storage Service
      1. S3 Overview
      2. Interacting with S3
      3. Buckets
      4. Objects
      5. Alternative Hostnames
      6. Access Control Lists
      7. Server Access Logging (Beta)
      8. Signed URIs
      9. Distributing Objects with BitTorrent
    7. 4. S3 Applications
      1. Share Large Files
      2. Online Backup with AWS::S3
      3. S3 Filesystem with ElasticDrive
      4. Mediated Access to S3 with JetS3t
    8. 5. EC2: Elastic Compute Cloud (Beta)
      1. EC2 Overview
      2. Interacting with EC2
      3. Keypairs
      4. Network Security by IP
      5. Finding Amazon Machine Images
      6. Controlling Instances
      7. Log In to an Instance
      8. Security Groups
      9. Managing and Sharing AMIs
      10. Console Output and Instance Reboot
    9. 6. Using EC2 Instances and Images
      1. EC2 Instances in Detail
      2. Data Management in EC2
      3. Modifying an AMI
      4. Registering an AMI
      5. Create an AMI from Scratch
    10. 7. EC2 Applications
      1. Dynamic DNS
      2. On-Demand VPN Server with OpenVPN
      3. Web Photo Album with Gallery 2
    11. 8. SQS: Simple Queue Service
      1. SQS Overview
      2. Interacting with SQS
      3. Queues
      4. Messages
      5. Queue Attributes
      6. Queue Access Control
    12. 9. SQS Applications
      1. Messaging Simulator
      2. Distributed Application Services with BOTO
      3. Automated Management of EC2 Instance Pools with Lifeguard
    13. 10. FPS: Flexible Payments Service (Beta)
      1. FPS Overview
      2. Interacting with FPS
      3. Managing Your Tokens
      4. Acquiring Third-Party Tokens
      5. Pay Now Widgets
    14. 11. FPS Transactions and Accounts
      1. Performing FPS Transactions
      2. Account Management and Information
    15. 12. FPS Advanced Topics
      1. Gatekeeper Language Guide
      2. Micropayments with FPS
      3. Building a Marketplace Application
      4. Subscribing to FPS Event Notifications
    16. 13. SimpleDB (Beta)
      1. SimpleDB Overview
      2. Interacting with SimpleDB
      3. Domains
      4. Items and Attributes
      5. Representing Data in SimpleDB
      6. Performing Queries
      7. Stock Price Database: A Mini SimpleDB Application
    17. A. AWS Resources
      1. AWS Online Resources
      2. Client Tools
      3. API Libraries
      4. Third-Party AWS Solutions
    18. B. AWS API Error Codes
      1. S3: Simple Storage Service
      2. EC2: Elastic Compute Cloud
      3. SQS: Simple Queue Service
      4. FPS: Flexible Payments Service
      5. SimpleDB
    19. Index
    20. About the Author
    21. Colophon
    22. SPECIAL OFFER: Upgrade this ebook with O’Reilly
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Representing Data in SimpleDB

The SimpleDB service stores all content as text, including the attribute values that store your data. The service does not recognize data types in the same way that a relational database does. This feature makes the service more flexible, because you can store any values you like without having to worry about whether they match a predefined schema; however, it also means that the service is only able to compare or sort values based on lexicographical (alphabetical) ordering. Whereas a traditional database can compare various data types based on a full understanding of what the particular type means, SimpleDB is oblivious to the standard data types and will assume that an alphabetical ordering always makes sense.

If you intend to perform queries that use comparison operators, such as less-than and greater-than, you will have to carefully encode any nontextual data you store in the service so that its lexicographical ordering is the same as the expected ordering for data of that type. You will also need to be able to decode these text values when you retrieve them from SimpleDB.

In this section we will define methods to encode and decode the most commonly used data types: Boolean, date, integer, and float. Our data-type encodings are designed to meet two criteria:

  1. The encoded values retain the expected ordering when sorted lexicographically.

  2. Encoded values include a special prefix character (!), to make it easy to recognize them, and a second character to ...

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