Introduction to Amazon Dynamodb (i)

DYNAMODB's data is stored on SSDS (solid state Drives, SSDs), which can store and access data of any size within the predicted low latency response time, while SSDs also have high I/O performance to handle large-scale request workloads. Let's take a look at the inappropriate usage scenarios for DYNAMODB: If you need to store large amounts of data, but the data is often accessed very low, dynamodb might not be appropriate.

DYNAMODB's data model is modeless and can be thought of as a simple key-value pattern. But what's special is that its primary key can be a single-attribute hash key or a composite hashing-range bond. For example, the hash primary key for a single attribute can be "UserID", which enables you to quickly read and write data about items associated with a specific user ID.

The hash-range key for a composite is indexed as a hash key element and as a range keys element. This multi-part key preserves the hierarchy between the first element value and the second element value. For example, a composite hash-range key might be a combination of "UserID" (hash) and "timestamp" (range). By keeping the hash key element constant, you can search within the range keys element to retrieve the item. This way you can use the Query API to retrieve all the items of a single UserID in a series of timestamps, and so on, which is why Dynamodb is very much like SQL in the same way that it is nosql, and it's possible to achieve both the benefits of SQL and NoSQL, and see how you design your database.

Now Dynamodb has replaced the location of the simpledb. If you know SimpleDB, you can look at the comparison between the two below:

1. Because Amazon SimpleDB automatically indexes all project properties, it supports flexible queries, like SQL, but affects performance and scalability.

2. SimpleDB is to limit the size of the table to 10g,dynamodb is to limit the total size of items (including attribute names and property values) to no more than 64KB, but not to limit the size of the table.

3. Amazon DynamoDB supports three types of scalar data: numeric, string, and binary. SimpleDB only supports strings.

4. The property value of DYNAMODB does not support null or an empty string.

Original: http://blog.csdn.net/hongchangfirst/article/details/25715029

Author: Hongchangfirst

Hongchangfirst's homepage: http://blog.csdn.net/hongchangfirst