Some things will not work as expected, since we're joining and also grouping, but that comes down to your knowledge of SQL and your database server and differs slightly between database servers. So, in this case, we need to use COUNT with some conditions. You can add more clauses to the above queries as you would usually do. How to use Ectos fragment for building complex queries. Want to show a users' posts with number of upvotes/downvotes of each post? Write posts_with_votes_count function. ![]() Want to show posts with the number of comments on the home page? Write posts_with_comments_count function. You can write functions in your context to load posts differently based on where you want to use them. Select: % group_by: p.idĪnd we get both votedown_count and voteup_count filled, without loading all of the votes. Now we can load the posts and fill comments_count field in a query like this: from p in Post, We can preload comments relation and then show the number of comments, but that would load all the comments unnecessarily.Ī solution can be to use a virtual field, for example, comments_count, like this: schema "posts" doįield :comments_count, :integer, virtual: true Now, consider we want to show a list of posts, with the number of comments each post has. We can use Ecto virtual fields to achieve this.Ĭonsider a schema defined as: schema "posts" do #. show a list of posts with the number of comments? Ever wanted to show a list of items along with the number of another related item, e.g. An addition to the Ecto query API called selectmerge this will take the existing select mapdictlist and merge it with the one supplied to selectmerge overwriting keys in the new map, if no select is currently defined it will use the value as is. # Fetch all post titles query = from p in Post, select : p. Now if we want to rename totalcount we'll need to do it in 3 different places. See the "Shared options" section at the module It is supported at least by Postgres and MySQL and defaults to 500. :max_rows - The number of rows to load from the database as we stream. For more information see the "Query Prefix" section of the This will be applied to all fromĪnd joins in the query that did not have a prefix previously givenĮither via the :prefix option on join/ from or via the schema. :prefix - The prefix to run the query on (such as the schema path May raise Ecto.QueryError if query validation fails. SQL adapters, such as Postgres and MySQL, can only enumerate a stream Returns a lazy enumerable that emits all entries from the data store delete_all ( stream(queryable :: (), opts :: Keyword.t()) :: Enum.t() Init/2 repository callback: def init ( _type, config ) do = from ( p in Post, where : p. Reading a system environment variable, such can be done via the Shows how to pass these configuration values: config :my_app, Repo, url : case the URL needs to be dynamically configured, for example by Options, like ssl, timeout and pool_size. URL can include query parameters to override shared and adapter-specific For example, the configurationĪbove could be rewritten to: config :my_app, Repo, url : schema can be of any value. :stacktrace- when true, publishes the stacktrace in telemetry events Use the :repo property in the event metadata for distinguishing Should keep the :telemetry_prefix consistent for each repo and Note that if you have multiple databases, you "Telemetry Events" section to see which events we recommendĪdapters to publish. Is based on the module name, so if your module is called :telemetry_prefix - we recommend adapters to publish events :pool_size - the size of the pool used by the connection module. If false,ĭisables logging for that repository. ![]() Can be any of Logger.level/0 values or false. :log - the log level used when logging the query with Elixir's :url - an URL that specifies storage information. ![]() ![]() It must always point to a subdirectory inside the priv directory :priv - the directory where to keep repository data, like :name- The name of the Repo supervisor process In spite of this, the following configuration values For this particular example, you can checkįor more information. Most of the configuration that goes into the config is specific For example, the repository: defmodule Repo do use Ecto.Repo, otp_app : :my_app, adapter : endĬould be configured with: config :my_app, Repo, database : "ecto_simple", username : "postgres", password : "postgres", hostname : "localhost" The :otp_app should point to an OTP application that has When used, the repository expects the :otp_app and :adapter as For example, Ecto ships with a Postgres adapter that Settings View Source Ecto.Repo behaviour (Ecto v3.10.3)Ī repository maps to an underlying data store, controlled by theĪdapter.
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