In a large table where a particularly embedded field is important enough to query, such as price in this case, it's a good idea to add an index. To find all reviews with such a structure and a price of 35, we can do the following: select * from metadata These can be queried in the DB with: select * from metadataĭigging in further we could examine only reviews with an an item field in the metadata and another nested field price. Over time, we might come to find that some reviews include an item field in their metadata. # How do we create an index a JSONB sub-field?Įnd Querying into JSONB fields with raw SQL It's particularly useful for situations involving user-submitted data, where we don't know the exact shape the data will come in.Ĭonsider this schema for user-submitted reviews: defmodule doĪdd :rating, :integer, default: 0, null: falseĬreate(unique_index(:reviews, )) Types contains additional data about the schema we are working with (fetched using the _schema_ method we saw in the previous section).Ĭhanges and errors are where it gets interesting.Ecto has a map type, which is implemented in Postgres as a JSONB field. The data and params are self-explanatory - the initial data and the params we fed to cast. Here's an example of how an Ecto query will look in AppSignal: Make sure the :otp_app configuration option matches your app’s OTP app name, and you’re all set! Instrumenting Ecto Queries with AppSignal in Your Elixir AppĪppSignal automatically instruments Ecto so you can get insights into Queries running in your Phoenix or Plug applications. Let's just take a very quick look at how you can monitor queries with AppSignal. There are many options available to configure the Repo or the adapter as per your needs, but that's out of the scope of this post. Then, each time a query is performed, this event triggers some query metadata that includes the time spent executing the query, retrieving the data from the database, and more.įor more details, see this full list of Ecto telemetry events. In addition, Ecto also automatically publishes telemetry events that can be monitored.įor example, to monitor statistics for all the queries sent to Ecto, you can subscribe to the event with telemetry. Monitor Queries Sent to Ecto from Your Elixir Application We will learn more about this when we get to the Query module. It also keeps a cache of all planned queries in an ETS table. A query planner starts that's responsible for planning and normalizing a query and its parameters.The Postgres adapter, in turn, starts a connection pool to your database using the DBConnection library. The Supervision tree initializes the adapter (, in this case), which is responsible for all communication with the database. A Supervisor starts that keeps track of all the processes required to keep Ecto working.The most common use cases include fetching records with /2, inserting new records with /2, and updating records with /2. Access to the full Ecto.Repo API included in MyApp.Repo.With the few lines of code above, you get the following: Application do use Application true def start ( _type, _args ) do children = # See # for other strategies and supported options opts = Supervisor. If you use mix phx.new to generate your Elixir project, this is done automatically for you.ĭefmodule MyApp. Simply call use Ecto.Repo inside your Repo module. provides an API to write migrations that interact with the database.It binds everything together and provides a centralized point of communication between a database and your application. If you use Ecto with a database (like most users out there), Repo is the heart of Ecto. In doing so, we'll demystify some of the apparent magic behind Ecto.Įcto is made up of four major modules - Repo, Query, Schema, and Changeset. In this post, we will dive into the internals of Ecto - its major components, their functions, and how they work. Ecto is a toolkit for mapping database objects to Elixir structs and provides a unified interface to manipulate that data.
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