DynamoDB Dynomite Querying Find By
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.
findwill raise aDynomite::Error::RecordNotFoundif the item is not found.find_bywill returnnil.findcan be passed a single element, Hash, or multiple elements with the Primary Keys. Underneath the hoodfindonly uses get_item for fast lookup.find_bycan be passed an Hash. It can use either get_item or where, which can call a query or scan