You're seeing just the function add_if_not_exists, go back to Ecto.Migration module for more information.
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add_if_not_exists(column, type, opts \\ [])

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Adds a column if it not exists yet when altering a table.

If the type value is a %Reference{}, it is used to add a constraint.

type and opts are exactly the same as in add/3.

This command is not reversible as Ecto does not know about column existence before the creation attempt.


alter table("posts") do
  add_if_not_exists :title, :string, default: ""