class ActiveRecord::ConnectionAdapters::SchemaCache

def columns_hash(table_name)

value is the column object.
Get the columns for a table as a hash, key is the column name

def columns_hash(table_name)
  @columns_hash.fetch(table_name) do
    @columns_hash[deep_deduplicate(table_name)] = columns(table_name).index_by(&:name).freeze
  end
end