# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 237
def initialize(connection, logger, connection_parameters, config)
  super(connection, logger)
  @connection_parameters, @config = connection_parameters, config

  # @local_tz is initialized as nil to avoid warnings when connect tries to use it
  @local_tz = nil
  @table_alias_length = nil
  @postgresql_version = nil

  connect
  @local_tz = execute('SHOW TIME ZONE').first["TimeZone"]
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 251
def active?
  if @connection.respond_to?(:status)
    @connection.status == PGconn::CONNECTION_OK
  else
    # We're asking the driver, not Active Record, 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 232
def adapter_name
  ADAPTER_NAME
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 813
def add_column(table_name, column_name, type, options = {})
  default = options[:default]
  notnull = options[:null] == false

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

  change_column_default(table_name, column_name, default) if options_include_default?(options)
  change_column_null(table_name, column_name, false, default) if notnull
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 529
def begin_db_transaction
  execute "BEGIN"
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 825
def change_column(table_name, column_name, type, options = {})
  quoted_table_name = quote_table_name(table_name)

  begin
    execute "ALTER TABLE #{quoted_table_name} ALTER COLUMN #{quote_column_name(column_name)} TYPE #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}"
  rescue ActiveRecord::StatementInvalid => e
    raise e if postgresql_version > 80000
    # This is PostgreSQL 7.x, so we have to use a more arcane way of doing it.
    begin
      begin_db_transaction
      tmp_column_name = "#{column_name}_ar_tmp"
      add_column(table_name, tmp_column_name, type, options)
      execute "UPDATE #{quoted_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
    rescue
      rollback_db_transaction
    end
  end

  change_column_default(table_name, column_name, options[:default]) if options_include_default?(options)
  change_column_null(table_name, column_name, options[:null], options[:default]) if options.key?(:null)
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 851
def change_column_default(table_name, column_name, default)
  execute "ALTER TABLE #{quote_table_name(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 855
def change_column_null(table_name, column_name, null, default = nil)
  unless null || default.nil?
    execute("UPDATE #{quote_table_name(table_name)} SET #{quote_column_name(column_name)}=#{quote(default)} WHERE #{quote_column_name(column_name)} IS NULL")
  end
  execute("ALTER TABLE #{quote_table_name(table_name)} ALTER #{quote_column_name(column_name)} #{null ? 'DROP' : 'SET'} NOT NULL")
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 716
def client_min_messages
  query('SHOW client_min_messages')[0][0]
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 721
def client_min_messages=(level)
  execute("SET client_min_messages TO '#{level}'")
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 678
def columns(table_name, name = nil)
  # Limit, precision, and scale are all handled by the 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 534
def commit_db_transaction
  execute "COMMIT"
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 573
def create_database(name, options = {})
  options = options.reverse_merge(:encoding => "utf8")

  option_string = options.symbolize_keys.sum do |key, value|
    case key
    when :owner
      " OWNER = \"#{value}\""
    when :template
      " TEMPLATE = \"#{value}\""
    when :encoding
      " ENCODING = '#{value}'"
    when :tablespace
      " TABLESPACE = \"#{value}\""
    when :connection_limit
      " CONNECTION LIMIT = #{value}"
    else
      ""
    end
  end

  execute "CREATE DATABASE #{quote_table_name(name)}#{option_string}"
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 547
def create_savepoint
  execute("SAVEPOINT #{current_savepoint_name}")
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 686
def current_database
  query('select current_database()')[0][0]
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 276
def disconnect!
  @connection.close rescue nil
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 691
def encoding
  query(          SELECT pg_encoding_to_char(pg_database.encoding) FROM pg_database          WHERE pg_database.datname LIKE '#{current_database}')[0][0]
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 323
def escape_bytea(value)
  @connection.escape_bytea(value) if value
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 513
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 871
def index_name_length
  63
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 644
def indexes(table_name, name = nil)
   schemas = schema_search_path.split(/,/).map { |p| quote(p) }.join(',')
   result = query(           SELECT distinct i.relname, d.indisunique, d.indkey, t.oid             FROM pg_class t, pg_class i, pg_index d           WHERE i.relkind = 'i'             AND d.indexrelid = i.oid             AND d.indisprimary = 'f'             AND t.oid = d.indrelid             AND t.relname = '#{table_name}'             AND i.relnamespace IN (SELECT oid FROM pg_namespace WHERE nspname IN (#{schemas}) )          ORDER BY i.relname, name)


  result.map do |row|
    index_name = row[0]
    unique = row[1] == 't'
    indkey = row[2].split(" ")
    oid = row[3]

    columns = Hash[query(          SELECT a.attnum, a.attname          FROM pg_attribute a          WHERE a.attrelid = #{oid}          AND a.attnum IN (#{indkey.join(",")}), "Columns for index #{row[0]} on #{table_name}")]

    column_names = columns.values_at(*indkey).compact
    column_names.empty? ? nil : IndexDefinition.new(table_name, index_name, unique, column_names)
  end.compact
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 425
def insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
  # Extract the table from the insert sql. Yuck.
  table = sql.split(" ", 4)[2].gsub('"', '')

  # Try an insert with 'returning id' if available (PG >= 8.2)
  if supports_insert_with_returning?
    pk, sequence_name = *pk_and_sequence_for(table) unless pk
    if pk
      id = select_value("#{sql} RETURNING #{quote_column_name(pk)}")
      clear_query_cache
      return id
    end
  end

  # Otherwise, insert then grab last_insert_id.
  if insert_id = super
    insert_id
  else
    # If neither pk nor sequence name is given, look them up.
    unless pk || sequence_name
      pk, sequence_name = *pk_and_sequence_for(table)
    end

    # If a pk is given, fallback to default sequence name.
    # Don't fetch last insert id for a table without a pk.
    if pk && sequence_name ||= default_sequence_name(table, pk)
      last_insert_id(table, sequence_name)
    end
  end
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 543
def outside_transaction?
  @connection.transaction_status == PGconn::PQTRANS_IDLE
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 801
def primary_key(table)
  pk_and_sequence = pk_and_sequence_for(table)
  pk_and_sequence && pk_and_sequence.first
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 373
def quote_table_name(name)
  schema, name_part = extract_pg_identifier_from_name(name.to_s)

  unless name_part
    quote_column_name(schema)
  else
    table_name, name_part = extract_pg_identifier_from_name(name_part)
    "#{quote_column_name(schema)}.#{quote_column_name(table_name)}"
  end
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 265
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 555
def release_savepoint
  execute("RELEASE SAVEPOINT #{current_savepoint_name}")
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 863
def rename_column(table_name, column_name, new_column_name)
  execute "ALTER TABLE #{quote_table_name(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 807
def rename_table(name, new_name)
  execute "ALTER TABLE #{quote_table_name(name)} RENAME TO #{quote_table_name(new_name)}"
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 539
def rollback_db_transaction
  execute "ROLLBACK"
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 551
def rollback_to_savepoint
  execute("ROLLBACK TO SAVEPOINT #{current_savepoint_name}")
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 711
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 703
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 420
def select_rows(sql, name = nil)
  select_raw(sql, name).last
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 295
def set_standard_conforming_strings
  old, self.client_min_messages = client_min_messages, 'panic'
  execute('SET standard_conforming_strings = on') rescue nil
ensure
  self.client_min_messages = old
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 306
def supports_ddl_transactions?
  true
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 302
def supports_insert_with_returning?
  postgresql_version >= 80200
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 310
def supports_savepoints?
  true
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 316
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 621
def table_exists?(name)
  name          = name.to_s
  schema, table = name.split('.', 2)

  unless table # A table was provided without a schema
    table  = schema
    schema = nil
  end

  if name =~ /^"/ # Handle quoted table names
    table  = name
    schema = nil
  end

  query(            SELECT COUNT(*)            FROM pg_tables            WHERE tablename = '#{table.gsub(/(^"|"$)/,'')}'            #{schema ? "AND schemaname = '#{schema}'" : ''}).first[0].to_i > 0
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 613
def tables(name = nil)
  query(          SELECT tablename          FROM pg_tables          WHERE schemaname = ANY (current_schemas(false)), name).map { |row| row[0] }
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 876
def type_to_sql(type, limit = nil, precision = nil, scale = nil)
  return super unless type.to_s == 'integer'
  return 'integer' unless limit

  case limit
    when 1, 2; 'smallint'
    when 3, 4; 'integer'
    when 5..8; 'bigint'
    else raise(ActiveRecordError, "No integer type has byte size #{limit}. Use a numeric with precision 0 instead.")
  end
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 330
def unescape_bytea(value)
  @connection.unescape_bytea(value) if value
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 524
def update_sql(sql, name = nil)
  super.cmd_tuples
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 911
def postgresql_version
  @postgresql_version ||=
    if @connection.respond_to?(:server_version)
      @connection.server_version
    else
      # Mimic PGconn.server_version behavior
      begin
        if query('SELECT version()')[0][0] =~ /PostgreSQL ([0-9.]+)/
          major, minor, tiny = $1.split(".")
          (major.to_i * 10000) + (minor.to_i * 100) + tiny.to_i
        else
          0
        end
      rescue
        0
      end
    end
end

  # File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 930
def translate_exception(exception, message)
  case exception.message
  when /duplicate key value violates unique constraint/
    RecordNotUnique.new(message, exception)
  when /violates foreign key constraint/
    InvalidForeignKey.new(message, exception)
  else
    super
  end
end