I'm playing around with DynamoDB Toolbox, and one thing that wasn't clear in my mind was how do I actually create a table using the definitions I made using Toolbox.
Quick GitHub issues search lead me to this issue
where Simlu was asking the same question, and the answer was "Do It Yourself".
I dread code duplication especially around things like table definitions - it's trivial to have all your tests pass, but in the end, the app fails in production because you have a mismatch between two definitions of the same thing.
I've made a little example repo and a helper. For now, feel free to just copy and paste it.
A helper like this might get into the dynamodb-toolbox itself, so I didn't create a package for it yet. But if jeremydaly decides this code should live in a package, I will do that.
import type { DynamoDB } from "aws-sdk";
type DynamoDBTypes = "string" | "number" | "binary";
type ToolboxData = {
partitionKey: string;
sortKey?: string;
attributes: {
[key: string]: DynamoDBTypes;
};
name: string;
};
function getAttributes(tableDefinition: DynamoDB.CreateTableInput) {
const typesMap: { [key: string]: DynamoDBTypes } = {
S: "string",
N: "number",
B: "binary",
};
return tableDefinition.AttributeDefinitions.reduce((previous, current) => {
return {
...previous,
[current.AttributeName]: typesMap[current.AttributeType],
};
}, {});
}
function getPartitionKey(tableDefinition: DynamoDB.CreateTableInput) {
return tableDefinition.KeySchema.find((k) => {
return k.KeyType.toUpperCase() === "HASH";
}).AttributeName;
}
function getSortKey(tableDefinition: DynamoDB.CreateTableInput) {
const rangeAttribute = tableDefinition.KeySchema.find((k) => {
return k.KeyType.toUpperCase() === "RANGE";
});
return rangeAttribute ? rangeAttribute.AttributeName : undefined;
}
export const dynamoSdkToToolbox = (
tableDefinition: DynamoDB.CreateTableInput
): ToolboxData => ({
partitionKey: getPartitionKey(tableDefinition),
attributes: getAttributes(tableDefinition),
sortKey: getSortKey(tableDefinition),
name: tableDefinition.TableName,
});
(there are tests for it in the example repo)
This is how to use it. Assuming you have a table definition using AWS SDK format:
import type { DynamoDB } from "aws-sdk";
export const tableDefinition: DynamoDB.CreateTableInput = {
TableName: "my-table",
AttributeDefinitions: [
{
AttributeType: "S",
AttributeName: "pk",
},
{
AttributeType: "S",
AttributeName: "sk",
},
],
KeySchema: [
{
AttributeName: "pk",
KeyType: "HASH",
},
{
AttributeName: "sk",
KeyType: "RANGE",
},
],
BillingMode: "PAY_PER_REQUEST"
};
src/tableDefinition.ts
pass it to the dynamoSdkToToolbox helper:
const DocumentClient = new DynamoDB.DocumentClient()
const MyTable = new Table({
...dynamoSdkToToolbox(tableDefinition),
DocumentClient
})
src/Customer.ts
This will set things like attributes, partitionKey, sortKey, and name for you - making sure they are and stay in sync.
Using the same table definition you can create a table (although you would probably use cloud formation or CDK for that, that's a topic for a separate article, but you might want to use a helper like this to transform the SDK definition to CDK https://gist.github.com/lgandecki/e7806462ce7c3d0d47ce65d44c5aa43d )
await dynamoDB.createTable(tableDefinition).promise()
src/index.ts
Feel free to play around with the code.
Let me know if you have any questions or thoughts in the comments below.
