Method: ActiveRecord::ConnectionAdapters::SchemaStatements#distinct_relation_for_primary_key

Defined in:
activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb

#distinct_relation_for_primary_key(relation) ⇒ Object

:nodoc:



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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1429

def distinct_relation_for_primary_key(relation) # :nodoc:
  primary_key_columns = Array(relation.primary_key).map do |column|
    visitor.compile(relation.table[column])
  end

  values = columns_for_distinct(
    primary_key_columns,
    relation.order_values
  )

  limited = relation.reselect(values).distinct!
  limited_ids = select_rows(limited.arel, "SQL").map do |results|
    results.last(Array(relation.primary_key).length) # ignores order values for MySQL and PostgreSQL
  end

  if limited_ids.empty?
    relation.none!
  else
    relation.where!(**Array(relation.primary_key).zip(limited_ids.transpose).to_h)
  end

  relation.limit_value = relation.offset_value = nil
  relation
end