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# MySQL / MariaDB default to a tx isolation level of "REPEATABLE READ". This

# patch sets the tx isolation level to "READ COMMITTED" for the duration of the

# connection.

#

# Reason: Repeatable Read semantics break the current implementation of the

# issue nested set model on MySQL when parallel modifications to the same tree

# happen.

#

module Mysql2ReadCommittedIsolation

  private

  def configure_connection

    super.tap do

      execute("SET SESSION tx_isolation='READ-COMMITTED'")

    end

  end

end

ActiveRecord::ConnectionAdapters::Mysql2Adapter.prepend Mysql2ReadCommittedIsolation