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@ -43,15 +43,72 @@ There are two types of primary key available:
As well as the index provided by the primary key, you can set one or more As well as the index provided by the primary key, you can set one or more
**secondary indices**. A secondary index lets you query the data in the table **secondary indices**. A secondary index lets you query the data in the table
using an alternate key. The main type of secondary index is a _global secondary using an alternate key.
index_. GSIs are useful for querying data that needs to be accessed using
non-primary key attributes. For example, if you have a Users table with UserID
as the primary key but often need to fetch users by their Email, a GSI on Email
would be appropriate.
**Global secondary indices** span the entire table allowing you to query accross A **global secondary index** is useful for querying data that needs to be
all partition keys whereas local secondary indices have the same partition key accessed using non-primary key attributes. For example, if you have a Users
as the table with UserID as the primary key but often need to fetch users by their
Email, a GSI on Email would be appropriate.
There are also **local secondary indices** but I don't understand the
difference.
## Real example
Below is a specification of the DynamoDB table I am using for my time-entries
project:
```json
{
"TableName": "TimeEntries",
"AttributeDefinitions": [
{
"AttributeName": "activity_start_end",
"AttributeType": "S"
},
{
"AttributeName": "start",
"AttributeType": "S"
},
{
"AttributeName": "activity_type",
"AttributeType": "S"
}
],
"KeySchema": [
{
"AttributeName": "activity_start_end",
"KeyType": "HASH"
}
],
"GlobalSecondaryIndexes": [
{
"IndexName": "StartIndex",
"KeySchema": [
{
"AttributeName": "start",
"KeyType": "HASH"
},
{
"AttributeName": "activity_type",
"KeyType": "RANGE"
}
],
"Projection": {
"ProjectionType": "ALL"
},
"ProvisionedThroughput": {
"ReadCapacityUnits": 1,
"WriteCapacityUnits": 1
}
}
],
"ProvisionedThroughput": {
"ReadCapacityUnits": 1,
"WriteCapacityUnits": 1
}
}
```
## Usage ## Usage