How to check if an index already exists in rails?

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Rails provides a straightforward way to check if an index exists using the index_exists? method.

Syntax

index_exists?(table_name, column_name, **options)

Example

Here’s an example of how to use index_exists?

class AddIndexToUsersEmail < ActiveRecord::Migration[7.1]
  def change
    unless index_exists?(:users, :email)
      add_index(:users, :email)
    end
  end
end

Following are some more examples of how to use index_exists? method:

# Checks if an index on multiple columns exists
index_exists?(:users, [:provider, :auth_id])

# Checks if a unique index exists
index_exists?(:users, :email, unique: true)

# Checks if an index with a custom name exists
index_exists?(:users, :email, name: "idx_email")

NOTE: This can also be re-written using the if_not_exists option in the add_index method.

class AddIndexToUsersEmail < ActiveRecord::Migration[7.1]
  def change
    add_index(:users, :email, if_not_exists: true)
  end
end

References

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