Insert/Update

Insert

Repo.insert(%User{email: "[e-mail]"}) 
#{:ok, [new User object...]}

Update

Unlike insert, get, or delete, update NEEDS a changeset

user
|> User.changeset(attrs)
|> Repo.update()
# {:ok, %User{} = user}
    
MyRepo.update_all(Post, set: [title: "New title"])

MyRepo.update_all(Post, inc: [visits: 1])

from(p in Post, where: p.id < 10, select: p.visits)
|> MyRepo.update_all(set: [title: "New title"])

Advanced

Insert or Update, Upsert

Works most of the time:

result =
  case MyRepo.get(Post, id) do
    nil  -> %Post{id: id}
    post -> post
  end
  |> Post.changeset(changes)
  |> MyRepo.insert_or_update

# {:ok, struct} or {:error, changeset}

Race condition immune

Method 1:

*note a unique index must be on daily_recording_id

    %Recording{}
    |> Recording.changeset(attrs)
    |> Repo.insert(on_conflict: :nothing, conflict_target: :daily_recording_id)

Method 2, reget on changeset error:

case get_chat_channel(attrs) do
  %ChatChannel{} = cc -> cc

  nil ->
  	case create_chat_channel(attrs) do
  		{:ok, cc} -> cc

  		{:error,
  			%Ecto.Changeset{
  				errors: [
  					unique_constraint:
  					{"has already been taken",
  						[constraint: :unique, constraint_name: "chat_channels_unique_index"]}
  				]
  			}} ->
  			%ChatChannel{} = cc = get_chat_channel(attrs)
end

Composing queries

# Create a query
query = from u in User, where: u.age > 18

# Extend the query
query = from u in query, select: u.name

Fragments

Allow you to define raw SQL

  from p in Post,
    where: is_nil(p.published_at) and
           fragment("lower(?)", p.title) == ^title

Custom Macros

defmodule ReactPhoenix.Helpers.QueryMacros do
  defmacro filter(agg, condition) do
    quote do
      fragment("? FILTER(WHERE ?)", unquote(agg), unquote(condition))
    end
  end

  defmacro type_count(id, condition) do
    quote do
      filter(count(unquote(id)), unquote(condition))
    end
  end
end

  import ReactPhoenix.Helpers.QueryMacros