DynamoDB Dynomite Querying Find By

Important: These docs are for the outdated Jets 5 versions and below. For the latest Jets docs: docs.rubyonjets.com

Primary Key

Dynomite will look for the primary key and then use find underneath the hood if Primary Key fields are found. If the Primary Key is not found, it’ll use where.

> Product.find_by(category: "Electronics", sku: 101)
=>
#<Product:0x00007f14ca8981a0
 @attrs={"updated_at"=>"2023-08-03T16:17:50Z", "created_at"=>"2023-08-03T16:17:50Z", "name"=>"Smartphone", "stock_quantity"=>0.5e2, "category"=>"Electronics", "price"=>0.5e3, "sku"=>0.101e3},
 @new_record=false>
>

If multiple results are found, IE: A products table with a category and sku. It will return the first found result. Example:

> Product.find_by(category: "Electronics")
=>
#<Product:0x00007f14c9c1ab58
 @attrs={"updated_at"=>"2023-08-03T16:17:50Z", "created_at"=>"2023-08-03T16:17:50Z", "name"=>"Smartphone", "stock_quantity"=>0.5e2, "category"=>"Electronics", "price"=>0.5e3, "sku"=>0.101e3},
 @new_record=false>
>

find_by cheatsheat

There are different ways to use find_by. Post has a partition key only, and Product has a composite key (both partition key and sort key) in these examples.

Product.find_by(category: "Electronics", sku: 101)
Product.find_by(category: "Electronics")
Product.find_by(category: "Electronics", sku: 101, name: "Smartphone", price: 500, stock_quantity: 50)
Product.find_by(price: 500, stock_quantity: 50)

find vs find_by

The find and find_by interfaces are different.

  • find will raise a Dynomite::Error::RecordNotFound if the item is not found. find_by will return nil.
  • find can be passed a single element, Hash, or multiple elements with the Primary Keys. Underneath the hood find only uses get_item for fast lookup.
  • find_by can be passed an Hash. It can use either get_item or where, which can call a query or scan