# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 230
      def initialize(connection, logger, connection_parameters, config)
        super(connection, logger)
        @connection_parameters, @config = connection_parameters, config

        connect
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 238
      def active?
        if @connection.respond_to?(:status)
          @connection.status == PGconn::CONNECTION_OK
        else
          # We're asking the driver, not ActiveRecord, so use @connection.query instead of #query
          @connection.query 'SELECT 1'
          true
        end
      # postgres-pr raises a NoMethodError when querying if no connection is available.
      rescue PGError, NoMethodError
        false
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 225
      def adapter_name
        'PostgreSQL'
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 583
      def add_column(table_name, column_name, type, options = {})
        default = options[:default]
        notnull = options[:null] == false

        quoted_column_name = quote_column_name(column_name)

        # Add the column.
        execute("ALTER TABLE #{table_name} ADD COLUMN #{quoted_column_name} #{type_to_sql(type, options[:limit])}")

        # Set optional default. If not null, update nulls to the new default.
        if options_include_default?(options)
          change_column_default(table_name, column_name, default)
          if notnull
            execute("UPDATE #{table_name} SET #{quoted_column_name}=#{quote(default, options[:column])} WHERE #{quoted_column_name} IS NULL")
          end
        end

        if notnull
          execute("ALTER TABLE #{table_name} ALTER #{quoted_column_name} SET NOT NULL")
        end
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 411
      def begin_db_transaction
        execute "BEGIN"
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 606
      def change_column(table_name, column_name, type, options = {})
        begin
          execute "ALTER TABLE #{table_name} ALTER COLUMN #{quote_column_name(column_name)} TYPE #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}"
        rescue ActiveRecord::StatementInvalid
          # This is PostgreSQL 7.x, so we have to use a more arcane way of doing it.
          begin_db_transaction
          tmp_column_name = "#{column_name}_ar_tmp"
          add_column(table_name, tmp_column_name, type, options)
          execute "UPDATE #{table_name} SET #{quote_column_name(tmp_column_name)} = CAST(#{quote_column_name(column_name)} AS #{type_to_sql(type, options[:limit], options[:precision], options[:scale])})"
          remove_column(table_name, column_name)
          rename_column(table_name, tmp_column_name, column_name)
          commit_db_transaction
        end

        if options_include_default?(options)
          change_column_default(table_name, column_name, options[:default])
        end
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 626
      def change_column_default(table_name, column_name, default)
        execute "ALTER TABLE #{table_name} ALTER COLUMN #{quote_column_name(column_name)} SET DEFAULT #{quote(default)}"
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 499
      def client_min_messages
        query('SHOW client_min_messages')[0][0]
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 504
      def client_min_messages=(level)
        execute("SET client_min_messages TO '#{level}'")
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 474
      def columns(table_name, name = nil)
        # Limit, precision, and scale are all handled by superclass.
        column_definitions(table_name).collect do |name, type, default, notnull|
          PostgreSQLColumn.new(name, default, type, notnull == 'f')
        end
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 416
      def commit_db_transaction
        execute "COMMIT"
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 263
      def disconnect!
        @connection.close rescue nil
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 395
      def execute(sql, name = nil)
        log(sql, name) do
          if @async
            @connection.async_exec(sql)
          else
            @connection.exec(sql)
          end
        end
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 439
      def indexes(table_name, name = nil)
        result = query("SELECT i.relname, d.indisunique, a.attname\nFROM pg_class t, pg_class i, pg_index d, pg_attribute a\nWHERE i.relkind = 'i'\nAND d.indexrelid = i.oid\nAND d.indisprimary = 'f'\nAND t.oid = d.indrelid\nAND t.relname = '\#{table_name}'\nAND a.attrelid = t.oid\nAND ( d.indkey[0]=a.attnum OR d.indkey[1]=a.attnum\nOR d.indkey[2]=a.attnum OR d.indkey[3]=a.attnum\nOR d.indkey[4]=a.attnum OR d.indkey[5]=a.attnum\nOR d.indkey[6]=a.attnum OR d.indkey[7]=a.attnum\nOR d.indkey[8]=a.attnum OR d.indkey[9]=a.attnum )\nORDER BY i.relname\n", name)

        current_index = nil
        indexes = []

        result.each do |row|
          if current_index != row[0]
            indexes << IndexDefinition.new(table_name, row[0], row[1] == "t", [])
            current_index = row[0]
          end

          indexes.last.columns << row[2]
        end

        indexes
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 377
      def insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
        table = sql.split(" ", 4)[2]
        super || last_insert_id(table, sequence_name || default_sequence_name(table, pk))
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 252
      def reconnect!
        if @connection.respond_to?(:reset)
          @connection.reset
          configure_connection
        else
          disconnect!
          connect
        end
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 636
      def remove_index(table_name, options = {})
        execute "DROP INDEX #{index_name(table_name, options)}"
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 631
      def rename_column(table_name, column_name, new_column_name)
        execute "ALTER TABLE #{table_name} RENAME COLUMN #{quote_column_name(column_name)} TO #{quote_column_name(new_column_name)}"
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 578
      def rename_table(name, new_name)
        execute "ALTER TABLE #{name} RENAME TO #{new_name}"
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 421
      def rollback_db_transaction
        execute "ROLLBACK"
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 494
      def schema_search_path
        @schema_search_path ||= query('SHOW search_path')[0][0]
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 486
      def schema_search_path=(schema_csv)
        if schema_csv
          execute "SET search_path TO #{schema_csv}"
          @schema_search_path = schema_csv
        end
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 372
      def select_rows(sql, name = nil)
        select_raw(sql, name).last
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 285
      def supports_migrations?
        true
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 290
      def supports_standard_conforming_strings?
        # Temporarily set the client message level above error to prevent unintentional
        # error messages in the logs when working on a PostgreSQL database server that
        # does not support standard conforming strings.
        client_min_messages_old = client_min_messages
        self.client_min_messages = 'panic'

        # postgres-pr does not raise an exception when client_min_messages is set higher
        # than error and "SHOW standard_conforming_strings" fails, but returns an empty
        # PGresult instead.
        has_support = execute('SHOW standard_conforming_strings')[0][0] rescue false
        self.client_min_messages = client_min_messages_old
        has_support
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 307
      def table_alias_length
        @table_alias_length ||= (postgresql_version >= 80000 ? query('SHOW max_identifier_length')[0][0].to_i : 63)
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 428
      def tables(name = nil)
        schemas = schema_search_path.split(/,/).map { |p| quote(p) }.join(',')
        query("SELECT tablename\nFROM pg_tables\nWHERE schemaname IN (\#{schemas})\n", name).map { |row| row[0] }
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 641
      def type_to_sql(type, limit = nil, precision = nil, scale = nil)
        return super unless type.to_s == 'integer'

        if limit.nil? || limit == 4
          'integer'
        elsif limit < 4
          'smallint'
        else
          'bigint'
        end
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 406
      def update_sql(sql, name = nil)
        super.cmdtuples
      end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 690
        def postgresql_version
          @postgresql_version ||=
            if @connection.respond_to?(:server_version)
              @connection.server_version
            else
              # Mimic PGconn.server_version behavior
              begin
                query('SELECT version()')[0][0] =~ /PostgreSQL (\d+)\.(\d+)\.(\d+)/
                ($1.to_i * 10000) + ($2.to_i * 100) + $3.to_i
              rescue
                0
              end
            end
        end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 749
        def configure_connection
          if @config[:encoding]
            if @connection.respond_to?(:set_client_encoding)
              @connection.set_client_encoding(@config[:encoding])
            else
              execute("SET client_encoding TO '#{@config[:encoding]}'")
            end
          end
          self.client_min_messages = @config[:min_messages] if @config[:min_messages]
          self.schema_search_path = @config[:schema_search_path] || @config[:schema_order]
        end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 711
        def connect
          @connection = PGconn.connect(*@connection_parameters)
          PGconn.translate_results = false if PGconn.respond_to?(:translate_results=)

          # Ignore async_exec and async_query when using postgres-pr.
          @async = @config[:allow_concurrency] && @connection.respond_to?(:async_exec)

          # Use escape string syntax if available. We cannot do this lazily when encountering
          # the first string, because that could then break any transactions in progress.
          # See: http://www.postgresql.org/docs/current/static/runtime-config-compatible.html
          # If PostgreSQL doesn't know the standard_conforming_strings parameter then it doesn't
          # support escape string syntax. Don't override the inherited quoted_string_prefix.
          if supports_standard_conforming_strings?
            self.class.instance_eval do
              define_method(:quoted_string_prefix) { 'E' }
            end
          end

          # Money type has a fixed precision of 10 in PostgreSQL 8.2 and below, and as of
          # PostgreSQL 8.3 it has a fixed precision of 19. PostgreSQLColumn.extract_precision
          # should know about this but can't detect it there, so deal with it here.
          money_precision = (postgresql_version >= 80300) ? 19 : 10
          PostgreSQLColumn.module_eval("def extract_precision(sql_type)\nif sql_type =~ /^money$/\n\#{money_precision}\nelse\nsuper\nend\nend\n")

          configure_connection
        end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 768
        def select(sql, name = nil)
          fields, rows = select_raw(sql, name)
          result = []
          for row in rows
            row_hash = {}
            fields.each_with_index do |f, i|
              row_hash[f] = row[i]
            end
            result << row_hash
          end
          result
        end

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 781
        def select_raw(sql, name = nil)
          res = execute(sql, name)
          results = res.result
          fields = []
          rows = []
          if results.length > 0
            fields = res.fields
            results.each do |row|
              hashed_row = {}
              row.each_index do |cell_index|
                # If this is a money type column and there are any currency symbols,
                # then strip them off. Indeed it would be prettier to do this in
                # PostgreSQLColumn.string_to_decimal but would break form input
                # fields that call value_before_type_cast.
                if res.type(cell_index) == MONEY_COLUMN_TYPE_OID
                  # Because money output is formatted according to the locale, there are two
                  # cases to consider (note the decimal seperators):
                  #  (1) $12,345,678.12        
                  #  (2) $12.345.678,12
                  case column = row[cell_index]
                    when /^-?\D+[\d,]+\.\d{2}$/  # (1)
                      row[cell_index] = column.gsub(/[^-\d\.]/, '')
                    when /^-?\D+[\d\.]+,\d{2}$/  # (2)
                      row[cell_index] = column.gsub(/[^-\d,]/, '').sub(/,/, '.')
                  end
                end

                hashed_row[fields[cell_index]] = column
              end
              rows << row
            end
          end
          res.clear
          return fields, rows
        end