Defines the columns Avram should use when performing an upsert

An "upsert" is short for "update or insert", or in Avram terminology a "create or update". If the values in an operation conflict with an existing record in the database, Avram updates that record. If there is no conflicting record, then Avram will create new one.

In Avram, you must define which columns Avram should look at when determining if a conflicting record exists. This is done using the macro Avram::Upsert.upsert_lookup_columns

Note: In almost every case the upsert_lookup_columns should have a unique index defined in the database to ensure no conflicting records are created, even from outside Avram.

Full Example

class User < BaseModel
  table do
    column name : String
    column email : String # This column has a unique index
  end
end

class SaveUser < User::SaveOperation
  # Can be one or more columns. In this case we choose just :email
  upsert_lookup_columns :email
end

# Will create a new row in the database since no row with
# `email: "[email protected]"` exists yet
SaveUser.upsert!(name: "Bobby", email: "[email protected]")

# Will update the name on the row we just created since the email is
# the same as one in the database
SaveUser.upsert!(name: "Bob", email: "[email protected]")

Difference between upsert and upsert!

There is an upsert and upsert! that work similarly to create and create!. upsert! will raise an error if the operation is invalid. Whereas upsert will yield the operation and the new record if the operation is valid, or the operation and nil if it is invalid.

# Will raise because the name is blank
SaveUser.upsert!(name: "", email: "[email protected]")

# Operation is invalid because name is blank
SaveUser.upsert(name: "", email: "[email protected]") do |operation, user|
  # `user` is `nil` because the operation is invalid.
  # If the `name` was valid `user` would be the newly created user
end