You're seeing just the function remove_if_exists, go back to Ecto.Migration module for more information.
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remove_if_exists(column, type)

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Removes a column only if the column exists when altering the constraint if the reference type is passed once it only has the constraint name on reference structure.

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


alter table("posts") do
  remove_if_exists :title, :string