text: # sql/crud.py
  # Copyright (C) 2005-2020 the SQLAlchemy authors and contributors
  # <see AUTHORS file>
  #
  # This module is part of SQLAlchemy and is released under
  # the MIT License: http://www.opensource.org/licenses/mit-license.php
  
  """Functions used by compiler.py to determine the parameters rendered
  within INSERT and UPDATE statements.
  
  """
  import functools
  import operator
  
  from . import coercions
  from . import dml
  from . import elements
  from . import roles
  from .. import exc
  from .. import util
  
  REQUIRED = util.symbol(
      "REQUIRED",
      """
  Placeholder for the value within a :class:`.BindParameter`
  which is required to be present when the statement is passed
  to :meth:`_engine.Connection.execute`.
  
  This symbol is typically used when a :func:`_expression.insert`
  or :func:`_expression.update` statement is compiled without parameter
  values present.
  
  """,
  )
  
  
  def _get_crud_params(compiler, stmt, compile_state, **kw):
      """create a set of tuples representing column/string pairs for use
      in an INSERT or UPDATE statement.
  
      Also generates the Compiled object's postfetch, prefetch, and
      returning column collections, used for default handling and ultimately
      populating the CursorResult's prefetch_cols() and postfetch_cols()
      collections.
  
      """
  
      compiler.postfetch = []
      compiler.insert_prefetch = []
      compiler.update_prefetch = []
      compiler.returning = []
  
      # getters - these are normally just column.key,
      # but in the case of mysql multi-table update, the rules for
      # .key must conditionally take tablename into account
      (
          _column_as_key,
          _getattr_col_key,
          _col_bind_name,
      ) = getters = _key_getters_for_crud_column(compiler, stmt, compile_state)
  
      compiler._key_getters_for_crud_column = getters
  
      # no parameters in the statement, no parameters in the
      # compiled params - return binds for all columns
      if compiler.column_keys is None and compile_state._no_parameters:
          return [
              (
                  c,
                  compiler.preparer.format_column(c),
                  _create_bind_param(compiler, c, None, required=True),
              )
              for c in stmt.table.columns
          ]
  
      if compile_state._has_multi_parameters:
          spd = compile_state._multi_parameters[0]
          stmt_parameter_tuples = list(spd.items())
      elif compile_state._ordered_values:
          spd = compile_state._dict_parameters
          stmt_parameter_tuples = compile_state._ordered_values
      elif compile_state._dict_parameters:
          spd = compile_state._dict_parameters
          stmt_parameter_tuples = list(spd.items())
      else:
          stmt_parameter_tuples = spd = None
  
      # if we have statement parameters - set defaults in the
      # compiled params
      if compiler.column_keys is None:
          parameters = {}
      elif stmt_parameter_tuples:
          parameters = dict(
              (_column_as_key(key), REQUIRED)
              for key in compiler.column_keys
              if key not in spd
          )
      else:
          parameters = dict(
              (_column_as_key(key), REQUIRED) for key in compiler.column_keys
          )
  
      # create a list of column assignment clauses as tuples
      values = []
  
      if stmt_parameter_tuples is not None:
          _get_stmt_parameter_tuples_params(
              compiler,
              compile_state,
              parameters,
              stmt_parameter_tuples,
              _column_as_key,
              values,
              kw,
          )
  
      check_columns = {}
  
      # special logic that only occurs for multi-table UPDATE
      # statements
      if compile_state.isupdate and compile_state.is_multitable:
          _get_multitable_params(
              compiler,
              stmt,
              compile_state,
              stmt_parameter_tuples,
              check_columns,
              _col_bind_name,
              _getattr_col_key,
              values,
              kw,
          )
  
      if compile_state.isinsert and stmt._select_names:
          _scan_insert_from_select_cols(
              compiler,
              stmt,
              compile_state,
              parameters,
              _getattr_col_key,
              _column_as_key,
              _col_bind_name,
              check_columns,
              values,
              kw,
          )
      else:
          _scan_cols(
              compiler,
              stmt,
              compile_state,
              parameters,
              _getattr_col_key,
              _column_as_key,
              _col_bind_name,
              check_columns,
              values,
              kw,
          )
  
      if parameters and stmt_parameter_tuples:
          check = (
              set(parameters)
              .intersection(_column_as_key(k) for k, v in stmt_parameter_tuples)
              .difference(check_columns)
          )
          if check:
              raise exc.CompileError(
                  "Unconsumed column names: %s"
                  % (", ".join("%s" % (c,) for c in check))
              )
  
      if compile_state._has_multi_parameters:
          values = _extend_values_for_multiparams(
              compiler, stmt, compile_state, values, kw
          )
      elif not values and compiler.for_executemany:
          # convert an "INSERT DEFAULT VALUES"
          # into INSERT (firstcol) VALUES (DEFAULT) which can be turned
          # into an in-place multi values.  This supports
          # insert_executemany_returning mode :)
          values = [
              (
                  stmt.table.columns[0],
                  compiler.preparer.format_column(stmt.table.columns[0]),
                  "DEFAULT",
              )
          ]
  
      return values
  
  
  def _create_bind_param(
      compiler, col, value, process=True, required=False, name=None, **kw
  ):
      if name is None:
          name = col.key
      bindparam = elements.BindParameter(
          name, value, type_=col.type, required=required
      )
      bindparam._is_crud = True
      if process:
          bindparam = bindparam._compiler_dispatch(compiler, **kw)
      return bindparam
  
  
  def _handle_values_anonymous_param(compiler, col, value, name, **kw):
      # the insert() and update() constructs as of 1.4 will now produce anonymous
      # bindparam() objects in the values() collections up front when given plain
      # literal values.  This is so that cache key behaviors, which need to
      # produce bound parameters in deterministic order without invoking any
      # compilation here, can be applied to these constructs when they include
      # values() (but not yet multi-values, which are not included in caching
      # right now).
      #
      # in order to produce the desired "crud" style name for these parameters,
      # which will also be targetable in engine/default.py through the usual
      # conventions, apply our desired name to these unique parameters by
      # populating the compiler truncated names cache with the desired name,
      # rather than having
      # compiler.visit_bindparam()->compiler._truncated_identifier make up a
      # name.  Saves on call counts also.
      if value.unique and isinstance(value.key, elements._truncated_label):
          compiler.truncated_names[("bindparam", value.key)] = name
  
      if value.type._isnull:
          # either unique parameter, or other bound parameters that were
          # passed in directly
          # set type to that of the column unconditionally
          value = value._with_binary_element_type(col.type)
  
      return value._compiler_dispatch(compiler, **kw)
  
  
  def _key_getters_for_crud_column(compiler, stmt, compile_state):
      if compile_state.isupdate and compile_state._extra_froms:
          # when extra tables are present, refer to the columns
          # in those extra tables as table-qualified, including in
          # dictionaries and when rendering bind param names.
          # the "main" table of the statement remains unqualified,
          # allowing the most compatibility with a non-multi-table
          # statement.
          _et = set(compile_state._extra_froms)
  
          c_key_role = functools.partial(
              coercions.expect_as_key, roles.DMLColumnRole
          )
  
          def _column_as_key(key):
              str_key = c_key_role(key)
              if hasattr(key, "table") and key.table in _et:
                  return (key.table.name, str_key)
              else:
                  return str_key
  
          def _getattr_col_key(col):
              if col.table in _et:
                  return (col.table.name, col.key)
              else:
                  return col.key
  
          def _col_bind_name(col):
              if col.table in _et:
                  return "%s_%s" % (col.table.name, col.key)
              else:
                  return col.key
  
      else:
          _column_as_key = functools.partial(
              coercions.expect_as_key, roles.DMLColumnRole
          )
          _getattr_col_key = _col_bind_name = operator.attrgetter("key")
  
      return _column_as_key, _getattr_col_key, _col_bind_name
  
  
  def _scan_insert_from_select_cols(
      compiler,
      stmt,
      compile_state,
      parameters,
      _getattr_col_key,
      _column_as_key,
      _col_bind_name,
      check_columns,
      values,
      kw,
  ):
  
      (
          need_pks,
          implicit_returning,
          implicit_return_defaults,
          postfetch_lastrowid,
      ) = _get_returning_modifiers(compiler, stmt, compile_state)
  
      cols = [stmt.table.c[_column_as_key(name)] for name in stmt._select_names]
  
      compiler._insert_from_select = stmt.select
  
      add_select_cols = []
      if stmt.include_insert_from_select_defaults:
          col_set = set(cols)
          for col in stmt.table.columns:
              if col not in col_set and col.default:
                  cols.append(col)
  
      for c in cols:
          col_key = _getattr_col_key(c)
          if col_key in parameters and col_key not in check_columns:
              parameters.pop(col_key)
              values.append((c, compiler.preparer.format_column(c), None))
          else:
              _append_param_insert_select_hasdefault(
                  compiler, stmt, c, add_select_cols, kw
              )
  
      if add_select_cols:
          values.extend(add_select_cols)
          compiler._insert_from_select = compiler._insert_from_select._generate()
          compiler._insert_from_select._raw_columns = tuple(
              compiler._insert_from_select._raw_columns
          ) + tuple(expr for col, col_expr, expr in add_select_cols)
  
  
  def _scan_cols(
      compiler,
      stmt,
      compile_state,
      parameters,
      _getattr_col_key,
      _column_as_key,
      _col_bind_name,
      check_columns,
      values,
      kw,
  ):
  
      (
          need_pks,
          implicit_returning,
          implicit_return_defaults,
          postfetch_lastrowid,
      ) = _get_returning_modifiers(compiler, stmt, compile_state)
  
      if compile_state._parameter_ordering:
          parameter_ordering = [
              _column_as_key(key) for key in compile_state._parameter_ordering
          ]
          ordered_keys = set(parameter_ordering)
          cols = [
              stmt.table.c[key]
              for key in parameter_ordering
              if isinstance(key, util.string_types) and key in stmt.table.c
          ] + [c for c in stmt.table.c if c.key not in ordered_keys]
  
      else:
          cols = stmt.table.columns
  
      for c in cols:
          col_key = _getattr_col_key(c)
  
          if col_key in parameters and col_key not in check_columns:
  
              _append_param_parameter(
                  compiler,
                  stmt,
                  compile_state,
                  c,
                  col_key,
                  parameters,
                  _col_bind_name,
                  implicit_returning,
                  implicit_return_defaults,
                  values,
                  kw,
              )
  
          elif compile_state.isinsert:
              if (
                  c.primary_key
                  and need_pks
                  and (
                      implicit_returning
                      or not postfetch_lastrowid
                      or c is not stmt.table._autoincrement_column
                  )
              ):
  
                  if implicit_returning:
                      _append_param_insert_pk_returning(
                          compiler, stmt, c, values, kw
                      )
                  else:
                      _append_param_insert_pk(compiler, stmt, c, values, kw)
  
              elif c.default is not None:
  
                  _append_param_insert_hasdefault(
                      compiler, stmt, c, implicit_return_defaults, values, kw
                  )
  
              elif c.server_default is not None:
                  if implicit_return_defaults and c in implicit_return_defaults:
                      compiler.returning.append(c)
                  elif not c.primary_key:
                      compiler.postfetch.append(c)
              elif implicit_return_defaults and c in implicit_return_defaults:
                  compiler.returning.append(c)
              elif (
                  c.primary_key
                  and c is not stmt.table._autoincrement_column
                  and not c.nullable
              ):
                  _warn_pk_with_no_anticipated_value(c)
  
          elif compile_state.isupdate:
              _append_param_update(
                  compiler,
                  compile_state,
                  stmt,
                  c,
                  implicit_return_defaults,
                  values,
                  kw,
              )
  
  
  def _append_param_parameter(
      compiler,
      stmt,
      compile_state,
      c,
      col_key,
      parameters,
      _col_bind_name,
      implicit_returning,
      implicit_return_defaults,
      values,
      kw,
  ):
  
      value = parameters.pop(col_key)
  
      col_value = compiler.preparer.format_column(
          c, use_table=compile_state.include_table_with_column_exprs
      )
  
      if coercions._is_literal(value):
          value = _create_bind_param(
              compiler,
              c,
              value,
              required=value is REQUIRED,
              name=_col_bind_name(c)
              if not compile_state._has_multi_parameters
              else "%s_m0" % _col_bind_name(c),
              **kw
          )
      elif value._is_bind_parameter:
          value = _handle_values_anonymous_param(
              compiler,
              c,
              value,
              name=_col_bind_name(c)
              if not compile_state._has_multi_parameters
              else "%s_m0" % _col_bind_name(c),
              **kw
          )
      else:
          if c.primary_key and implicit_returning:
              compiler.returning.append(c)
              value = compiler.process(value.self_group(), **kw)
          elif implicit_return_defaults and c in implicit_return_defaults:
              compiler.returning.append(c)
              value = compiler.process(value.self_group(), **kw)
          else:
              # postfetch specifically means, "we can SELECT the row we just
              # inserted by primary key to get back the server generated
              # defaults". so by definition this can't be used to get the primary
              # key value back, because we need to have it ahead of time.
              if not c.primary_key:
                  compiler.postfetch.append(c)
              value = compiler.process(value.self_group(), **kw)
      values.append((c, col_value, value))
  
  
  def _append_param_insert_pk_returning(compiler, stmt, c, values, kw):
      """Create a primary key expression in the INSERT statement and
      possibly a RETURNING clause for it.
  
      If the column has a Python-side default, we will create a bound
      parameter for it and "pre-execute" the Python function.  If
      the column has a SQL expression default, or is a sequence,
      we will add it directly into the INSERT statement and add a
      RETURNING element to get the new value.  If the column has a
      server side default or is marked as the "autoincrement" column,
      we will add a RETRUNING element to get at the value.
  
      If all the above tests fail, that indicates a primary key column with no
      noted default generation capabilities that has no parameter passed;
      raise an exception.
  
      """
      if c.default is not None:
          if c.default.is_sequence:
              if compiler.dialect.supports_sequences and (
                  not c.default.optional
                  or not compiler.dialect.sequences_optional
              ):
                  values.append(
                      (
                          c,
                          compiler.preparer.format_column(c),
                          compiler.process(c.default, **kw),
                      )
                  )
              compiler.returning.append(c)
          elif c.default.is_clause_element:
              values.append(
                  (
                      c,
                      compiler.preparer.format_column(c),
                      compiler.process(c.default.arg.self_group(), **kw),
                  )
              )
              compiler.returning.append(c)
          else:
              values.append(
                  (
                      c,
                      compiler.preparer.format_column(c),
                      _create_insert_prefetch_bind_param(compiler, c, **kw),
                  )
              )
      elif c is stmt.table._autoincrement_column or c.server_default is not None:
          compiler.returning.append(c)
      elif not c.nullable:
          # no .default, no .server_default, not autoincrement, we have
          # no indication this primary key column will have any value
          _warn_pk_with_no_anticipated_value(c)
  
  
  def _create_insert_prefetch_bind_param(
      compiler, c, process=True, name=None, **kw
  ):
      param = _create_bind_param(
          compiler, c, None, process=process, name=name, **kw
      )
      compiler.insert_prefetch.append(c)
      return param
  
  
  def _create_update_prefetch_bind_param(
      compiler, c, process=True, name=None, **kw
  ):
      param = _create_bind_param(
          compiler, c, None, process=process, name=name, **kw
      )
      compiler.update_prefetch.append(c)
      return param
  
  
  class _multiparam_column(elements.ColumnElement):
      _is_multiparam_column = True
  
      def __init__(self, original, index):
          self.index = index
          self.key = "%s_m%d" % (original.key, index + 1)
          self.original = original
          self.default = original.default
          self.type = original.type
  
      def compare(self, other, **kw):
          raise NotImplementedError()
  
      def _copy_internals(self, other, **kw):
          raise NotImplementedError()
  
      def __eq__(self, other):
          return (
              isinstance(other, _multiparam_column)
              and other.key == self.key
              and other.original == self.original
          )
  
  
  def _process_multiparam_default_bind(compiler, stmt, c, index, kw):
  
      if not c.default:
          raise exc.CompileError(
              "INSERT value for column %s is explicitly rendered as a bound"
              "parameter in the VALUES clause; "
              "a Python-side value or SQL expression is required" % c
          )
      elif c.default.is_clause_element:
          return compiler.process(c.default.arg.self_group(), **kw)
      else:
          col = _multiparam_column(c, index)
          if isinstance(stmt, dml.Insert):
              return _create_insert_prefetch_bind_param(compiler, col, **kw)
          else:
              return _create_update_prefetch_bind_param(compiler, col, **kw)
  
  
  def _append_param_insert_pk(compiler, stmt, c, values, kw):
      """Create a bound parameter in the INSERT statement to receive a
      'prefetched' default value.
  
      The 'prefetched' value indicates that we are to invoke a Python-side
      default function or expliclt SQL expression before the INSERT statement
      proceeds, so that we have a primary key value available.
  
      if the column has no noted default generation capabilities, it has
      no value passed in either; raise an exception.
  
      """
  
      if (
          # column has a Python-side default
          c.default is not None
          and (
              # and it either is not a sequence, or it is and we support
              # sequences and want to invoke it
              not c.default.is_sequence
              or (
                  compiler.dialect.supports_sequences
                  and (
                      not c.default.optional
                      or not compiler.dialect.sequences_optional
                  )
              )
          )
      ) or (
          # column is the "autoincrement column"
          c is stmt.table._autoincrement_column
          and (
              # and it's either a "sequence" or a
              # pre-executable "autoincrement" sequence
              compiler.dialect.supports_sequences
              or compiler.dialect.preexecute_autoincrement_sequences
          )
      ):
          values.append(
              (
                  c,
                  compiler.preparer.format_column(c),
                  _create_insert_prefetch_bind_param(compiler, c, **kw),
              )
          )
      elif c.default is None and c.server_default is None and not c.nullable:
          # no .default, no .server_default, not autoincrement, we have
          # no indication this primary key column will have any value
          _warn_pk_with_no_anticipated_value(c)
  
  
  def _append_param_insert_hasdefault(
      compiler, stmt, c, implicit_return_defaults, values, kw
  ):
  
      if c.default.is_sequence:
          if compiler.dialect.supports_sequences and (
              not c.default.optional or not compiler.dialect.sequences_optional
          ):
              values.append(
                  (
                      c,
                      compiler.preparer.format_column(c),
                      compiler.process(c.default, **kw),
                  )
              )
              if implicit_return_defaults and c in implicit_return_defaults:
                  compiler.returning.append(c)
              elif not c.primary_key:
                  compiler.postfetch.append(c)
      elif c.default.is_clause_element:
          values.append(
              (
                  c,
                  compiler.preparer.format_column(c),
                  compiler.process(c.default.arg.self_group(), **kw),
              )
          )
  
          if implicit_return_defaults and c in implicit_return_defaults:
              compiler.returning.append(c)
          elif not c.primary_key:
              # don't add primary key column to postfetch
              compiler.postfetch.append(c)
      else:
          values.append(
              (
                  c,
                  compiler.preparer.format_column(c),
                  _create_insert_prefetch_bind_param(compiler, c, **kw),
              )
          )
  
  
  def _append_param_insert_select_hasdefault(compiler, stmt, c, values, kw):
  
      if c.default.is_sequence:
          if compiler.dialect.supports_sequences and (
              not c.default.optional or not compiler.dialect.sequences_optional
          ):
              values.append(
                  (c, compiler.preparer.format_column(c), c.default.next_value())
              )
      elif c.default.is_clause_element:
          values.append(
              (c, compiler.preparer.format_column(c), c.default.arg.self_group())
          )
      else:
          values.append(
              (
                  c,
                  compiler.preparer.format_column(c),
                  _create_insert_prefetch_bind_param(
                      compiler, c, process=False, **kw
                  ),
              )
          )
  
  
  def _append_param_update(
      compiler, compile_state, stmt, c, implicit_return_defaults, values, kw
  ):
  
      include_table = compile_state.include_table_with_column_exprs
      if c.onupdate is not None and not c.onupdate.is_sequence:
          if c.onupdate.is_clause_element:
              values.append(
                  (
                      c,
                      compiler.preparer.format_column(
                          c, use_table=include_table,
                      ),
                      compiler.process(c.onupdate.arg.self_group(), **kw),
                  )
              )
              if implicit_return_defaults and c in implicit_return_defaults:
                  compiler.returning.append(c)
              else:
                  compiler.postfetch.append(c)
          else:
              values.append(
                  (
                      c,
                      compiler.preparer.format_column(
                          c, use_table=include_table,
                      ),
                      _create_update_prefetch_bind_param(compiler, c, **kw),
                  )
              )
      elif c.server_onupdate is not None:
          if implicit_return_defaults and c in implicit_return_defaults:
              compiler.returning.append(c)
          else:
              compiler.postfetch.append(c)
      elif (
          implicit_return_defaults
          and stmt._return_defaults is not True
          and c in implicit_return_defaults
      ):
          compiler.returning.append(c)
  
  
  def _get_multitable_params(
      compiler,
      stmt,
      compile_state,
      stmt_parameter_tuples,
      check_columns,
      _col_bind_name,
      _getattr_col_key,
      values,
      kw,
  ):
      normalized_params = dict(
          (coercions.expect(roles.DMLColumnRole, c), param)
          for c, param in stmt_parameter_tuples
      )
  
      include_table = compile_state.include_table_with_column_exprs
  
      affected_tables = set()
      for t in compile_state._extra_froms:
          for c in t.c:
              if c in normalized_params:
                  affected_tables.add(t)
                  check_columns[_getattr_col_key(c)] = c
                  value = normalized_params[c]
  
                  col_value = compiler.process(c, include_table=include_table)
                  if coercions._is_literal(value):
                      value = _create_bind_param(
                          compiler,
                          c,
                          value,
                          required=value is REQUIRED,
                          name=_col_bind_name(c),
                          **kw  # TODO: no test coverage for literal binds here
                      )
                  elif value._is_bind_parameter:
                      value = _handle_values_anonymous_param(
                          compiler, c, value, name=_col_bind_name(c), **kw
                      )
                  else:
                      compiler.postfetch.append(c)
                      value = compiler.process(value.self_group(), **kw)
                  values.append((c, col_value, value))
      # determine tables which are actually to be updated - process onupdate
      # and server_onupdate for these
      for t in affected_tables:
          for c in t.c:
              if c in normalized_params:
                  continue
              elif c.onupdate is not None and not c.onupdate.is_sequence:
                  if c.onupdate.is_clause_element:
                      values.append(
                          (
                              c,
                              compiler.process(c, include_table=include_table),
                              compiler.process(
                                  c.onupdate.arg.self_group(), **kw
                              ),
                          )
                      )
                      compiler.postfetch.append(c)
                  else:
                      values.append(
                          (
                              c,
                              compiler.process(c, include_table=include_table),
                              _create_update_prefetch_bind_param(
                                  compiler, c, name=_col_bind_name(c), **kw
                              ),
                          )
                      )
              elif c.server_onupdate is not None:
                  compiler.postfetch.append(c)
  
  
  def _extend_values_for_multiparams(compiler, stmt, compile_state, values, kw):
      values_0 = values
      values = [values]
  
      for i, row in enumerate(compile_state._multi_parameters[1:]):
          extension = []
          for (col, col_expr, param) in values_0:
              if col in row or col.key in row:
                  key = col if col in row else col.key
  
                  if coercions._is_literal(row[key]):
                      new_param = _create_bind_param(
                          compiler,
                          col,
                          row[key],
                          name="%s_m%d" % (col.key, i + 1),
                          **kw
                      )
                  else:
                      new_param = compiler.process(row[key].self_group(), **kw)
              else:
                  new_param = _process_multiparam_default_bind(
                      compiler, stmt, col, i, kw
                  )
  
              extension.append((col, col_expr, new_param))
  
          values.append(extension)
  
      return values
  
  
  def _get_stmt_parameter_tuples_params(
      compiler,
      compile_state,
      parameters,
      stmt_parameter_tuples,
      _column_as_key,
      values,
      kw,
  ):
  
      for k, v in stmt_parameter_tuples:
          colkey = _column_as_key(k)
          if colkey is not None:
              parameters.setdefault(colkey, v)
          else:
              # a non-Column expression on the left side;
              # add it to values() in an "as-is" state,
              # coercing right side to bound param
  
              col_expr = compiler.process(
                  k, include_table=compile_state.include_table_with_column_exprs
              )
  
              if coercions._is_literal(v):
                  v = compiler.process(
                      elements.BindParameter(None, v, type_=k.type), **kw
                  )
              else:
                  v = compiler.process(v.self_group(), **kw)
  
              values.append((k, col_expr, v))
  
  
  def _get_returning_modifiers(compiler, stmt, compile_state):
  
      need_pks = (
          compile_state.isinsert
          and not stmt._inline
          and (
              not compiler.for_executemany
              or (
                  compiler.dialect.insert_executemany_returning
                  and stmt._return_defaults
              )
          )
          and not stmt._returning
          and not compile_state._has_multi_parameters
      )
  
      implicit_returning = (
          need_pks
          and compiler.dialect.implicit_returning
          and stmt.table.implicit_returning
      )
  
      if compile_state.isinsert:
          implicit_return_defaults = implicit_returning and stmt._return_defaults
      elif compile_state.isupdate:
          implicit_return_defaults = (
              compiler.dialect.implicit_returning
              and stmt.table.implicit_returning
              and stmt._return_defaults
          )
      else:
          # this line is unused, currently we are always
          # isinsert or isupdate
          implicit_return_defaults = False  # pragma: no cover
  
      if implicit_return_defaults:
          if stmt._return_defaults is True:
              implicit_return_defaults = set(stmt.table.c)
          else:
              implicit_return_defaults = set(stmt._return_defaults)
  
      postfetch_lastrowid = need_pks and compiler.dialect.postfetch_lastrowid
  
      return (
          need_pks,
          implicit_returning,
          implicit_return_defaults,
          postfetch_lastrowid,
      )
  
  
  def _warn_pk_with_no_anticipated_value(c):
      msg = (
          "Column '%s.%s' is marked as a member of the "
          "primary key for table '%s', "
          "but has no Python-side or server-side default generator indicated, "
          "nor does it indicate 'autoincrement=True' or 'nullable=True', "
          "and no explicit value is passed.  "
          "Primary key columns typically may not store NULL."
          % (c.table.fullname, c.name, c.table.fullname)
      )
      if len(c.table.primary_key) > 1:
          msg += (
              " Note that as of SQLAlchemy 1.1, 'autoincrement=True' must be "
              "indicated explicitly for composite (e.g. multicolumn) primary "
              "keys if AUTO_INCREMENT/SERIAL/IDENTITY "
              "behavior is expected for one of the columns in the primary key. "
              "CREATE TABLE statements are impacted by this change as well on "
              "most backends."
          )
      util.warn(msg)
  