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October 19, 2023 18:15
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Multi-tenant querying with GraphQL::Dataloader
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| require "bundler/inline" | |
| gemfile do | |
| gem "graphql" | |
| end | |
| # Here's a pretend DB with three tenants: | |
| DATA = { | |
| "food_lion" => [ | |
| { id: 1, name: "Mayo" }, | |
| { id: 2, name: "Bread" }, | |
| { id: 3, name: "Apple" }, | |
| ], | |
| "books_a_million" => [ | |
| { id: 1, name: "Hannah Coulter" }, | |
| { id: 2, name: "Ruby Under a Microscope" }, | |
| { id: 3, name: "American Farmstead Cheese" }, | |
| ], | |
| "crozet_hardware" => [ | |
| { id: 1, name: "Paint brush" }, | |
| { id: 2, name: "Flashlight" }, | |
| { id: 3, name: "Gate hinge" }, | |
| ] | |
| } | |
| # Here's a dataloader source which selects by tenant: | |
| class PerTenantRecordSource < GraphQL::Dataloader::Source | |
| def initialize(tenant) | |
| @tenant = tenant | |
| end | |
| def fetch(ids) | |
| puts "Selecting from #{@tenant.inspect}: #{ids}" | |
| # IRL you'd query ActiveRecord, setting the tenant here | |
| tenant_data = DATA[@tenant] | |
| ids.map { |id| tenant_data.find { |d| d[:id] == id } } | |
| end | |
| end | |
| class ExampleSchema < GraphQL::Schema | |
| class Product < GraphQL::Schema::Object | |
| field :name, String | |
| end | |
| class Query < GraphQL::Schema::Object | |
| field :product, Product do | |
| argument :id, Integer | |
| end | |
| def product(id:) | |
| # This field passes the tenant to dataloader: | |
| dataloader.with(PerTenantRecordSource, context[:tenant]).load(id) | |
| end | |
| end | |
| use GraphQL::Dataloader | |
| query(Query) | |
| end | |
| result = ExampleSchema.multiplex([ | |
| { query: "{ product(id: 1) { name } }", context: { tenant: "food_lion" } }, | |
| { query: "{ product(id: 1) { name } }", context: { tenant: "books_a_million" } }, | |
| { query: "{ p1: product(id: 1) { name } p2: product(id: 2) { name } }", context: { tenant: "crozet_hardware" } }, | |
| { query: "{ p1: product(id: 1) { name } p2: product(id: 2) { name } p5: product(id: 5) { name } }", context: { tenant: "food_lion" } }, | |
| ]) | |
| # Under the hood, dataloader runs these separately: | |
| # | |
| # Selecting from "food_lion": [1, 2, 3] | |
| # Selecting from "books_a_million": [1] | |
| # Selecting from "crozet_hardware": [1, 2] | |
| pp result.map(&:to_h) | |
| # [ | |
| # {"data"=>{"product"=>{"name"=>"Mayo"}}}, | |
| # {"data"=>{"product"=>{"name"=>"Hannah Coulter"}}}, | |
| # {"data"=>{"p1"=>{"name"=>"Paint brush"}, "p2"=>{"name"=>"Flashlight"}}}, | |
| # {"data"=>{"p1"=>{"name"=>"Mayo"}, "p2"=>{"name"=>"Bread"}, "p5"=>nil}} | |
| # ] |
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