Crate aws_dynamo_derive

dynamo-derive

Helper crate for aws-sdk-dynamodb.

Generates conversion codes from Rust primitive types to AWS DynamoDB types. Works well with nested types!

Example

use aws_dynamo_derive::{Item, Table};

#[derive(Table)]
struct Foo {
    #[aws_dynamo(hash_key)]
    pub name: String,
    pub value: Value
}

#[derive(Item, Clone)]
struct Value {
    pub numbers: Vec<u64>,
    pub list_of_ss: Vec<Vec<String>>, 
}

this generates

{
    "Value": M(
        {
            "Numbers": Ns(["1", "2", "3"]), 
            "ListOfSs": L([Ss(["one"]), Ss(["two"]), Ss(["three"])])
        }
    ), 
    "Name": S("foo_value")
}

KeySchemas and AttributeDefinitions

Struct fields decorated with #[aws_dynamo(hash_key)] add KeyType::Hash KeySchemas, and by data type of the fields, macro maps those to AttributeDefinitions.

Available KeySchemas:

• range_key
• hash_key

AttributeDefinition mappings:

• String -> S
• i8 | u8 | .. | u128 -> N
• Blob -> B

AttributeValue

• String -> S
• bool -> BOOL
• Blob -> B
• i8 | u8 | .. | u128 -> N
• Vec<String> -> SS
• For T: i8 | u8 | .. | u128, Vec<T> -> NS
• Vec<Blob> -> Bs
• Option<()> -> NULL
• If T is Vec<T> but not SS | NS | Bs -> L
• HashMap<String, T> -> M, automatically converts inner values of HashMap to AttributeValue types.
• struct that derives Item and be converted into AttributeValue.

GlobalSecondaryIndex

There are many things to set for GSI compared to other fields. This API only provides KeySchemaElement. get_global_secondary_index_key_schemas returns a HashMap of { index name: [KeySchemaElement] } with the value given to the attribute. By getting the Vec<KeySchemaElement> using the index_name as the key of HashMap, you can pass the retrieved value to the set_key_schema method of GlobalSecondaryIndexBuilder.

AttributeValue conversions

from_attribute_value converts HashMap<String, AttributeValue> to Rust types. If any field type does not match the given AttributeValue type, it returns Err(AttributeValue).

Downsides

The macro tries to convert all possible types, which leads to extra allocation while iterating items of collection types like Vector or HashMap. If the type is super complex and heavy, you might need to benchmark before using it.

Derive Macros

• Item
  Derive macro for AwsDynamoDb Item
• Table
  Derive macro for AwsDynamoDb table