diff --git a/datajoint/declare.py b/datajoint/declare.py
index 8b357b8c0..4f2cd2463 100644
--- a/datajoint/declare.py
+++ b/datajoint/declare.py
@@ -114,6 +114,5 @@ def compile_attribute(line, in_key=False):
         else:
             match['default'] = 'NOT NULL'
     match['comment'] = match['comment'].replace('"', '\\"')   # escape double quotes in comment
-    sql = ('`{name}` {type} {default}' + (' COMMENT "{comment}"' if match['comment'] else '')
-           ).format(**match)
+    sql = ('`{name}` {type} {default}' + (' COMMENT "{comment}"' if match['comment'] else '')).format(**match)
     return match['name'], sql
diff --git a/datajoint/fetch.py b/datajoint/fetch.py
index 955116892..395885528 100644
--- a/datajoint/fetch.py
+++ b/datajoint/fetch.py
@@ -1,4 +1,5 @@
 from collections import OrderedDict
+from collections.abc import Callable, Iterable
 from functools import wraps
 import warnings
 from .blob import unpack
@@ -47,7 +48,7 @@ def ret(*args, **kwargs):
     return ret
 
 
-class Fetch:
+class Fetch(Iterable, Callable):
     """
     A fetch object that handles retrieving elements from the database table.
 
@@ -59,9 +60,7 @@ def __init__(self, relation):
             self.behavior = dict(relation.behavior)
             self._relation = relation._relation
         else:
-            self.behavior = dict(
-                offset=None, limit=None, order_by=None, as_dict=False
-            )
+            self.behavior = dict(offset=None, limit=None, order_by=None, as_dict=False)
             self._relation = relation
 
     @copy_first
@@ -240,7 +239,7 @@ def __len__(self):
         return len(self._relation)
 
 
-class Fetch1:
+class Fetch1(Callable):
     """
     Fetch object for fetching exactly one row.
 
diff --git a/datajoint/heading.py b/datajoint/heading.py
index e3986c032..7a742416b 100644
--- a/datajoint/heading.py
+++ b/datajoint/heading.py
@@ -164,9 +164,6 @@ def init_from_database(self, conn, database, table_name):
             attr['string'] = bool(re.match(r'(var)?char|enum|date|time|timestamp', attr['type']))
             attr['is_blob'] = bool(re.match(r'(tiny|medium|long)?blob', attr['type']))
 
-            # strip field lengths off integer types
-            attr['type'] = re.sub(r'((tiny|small|medium|big)?int)\(\d+\)', r'\1', attr['type'])
-
             attr['computation'] = None
             if not (attr['numeric'] or attr['string'] or attr['is_blob']):
                 raise DataJointError('Unsupported field type {field} in `{database}`.`{table_name}`'.format(
diff --git a/datajoint/relation.py b/datajoint/relation.py
index 9f3ba6f49..ce02351dd 100644
--- a/datajoint/relation.py
+++ b/datajoint/relation.py
@@ -1,4 +1,5 @@
-from collections import Mapping, OrderedDict
+from collections.abc import Mapping
+from collections import OrderedDict
 import numpy as np
 import logging
 import abc
diff --git a/datajoint/relational_operand.py b/datajoint/relational_operand.py
index 2374f5d1b..d1733d67b 100644
--- a/datajoint/relational_operand.py
+++ b/datajoint/relational_operand.py
@@ -1,3 +1,4 @@
+from collections.abc import Iterable, Mapping
 import numpy as np
 import abc
 import re
@@ -103,7 +104,7 @@ def aggregate(self, group, *attributes, **renamed_attributes):
         if not isinstance(group, RelationalOperand):
             raise DataJointError('The second argument must be a relation')
         return Aggregation(
-            Join(self, Subquery(group), left=True),
+            Join(self, group, left=True),
             *attributes, **renamed_attributes)
 
     def __and__(self, restriction):
@@ -112,8 +113,7 @@ def __and__(self, restriction):
         :return: a restricted copy of the argument
         """
         ret = copy(self)
-        ret._restrictions = list(ret.restrictions)  # copy restriction list
-        ret.restrict(restriction)
+        ret.restrict(restriction, *ret.restrictions)
         return ret
 
     def restrict(self, *restrictions):
@@ -124,7 +124,8 @@ def restrict(self, *restrictions):
         However, each member of restrictions can be a list of conditions, which are combined with OR.
         :param restrictions: list of restrictions.
         """
-        restrictions = [r for r in restrictions if r is not None]  # remove Nones
+        # remove Nones and duplicates
+        restrictions = [r for r in restrictions if r is not None and r not in self.restrictions]
         if restrictions:
             if any(is_empty_set(r) for r in restrictions):
                 # if any condition is an empty list, return empty
@@ -135,6 +136,14 @@ def restrict(self, *restrictions):
                 else:
                     self._restrictions.extend(restrictions)
 
+    def attributes_in_restrictions(self):
+        """
+        :return: list of attributes that are probably used in the restrictions.
+        This is used internally for optimizing SQL statements
+        """
+        where_clause = self.where_clause
+        return set(name for name in self.heading.names if name in where_clause)
+
     def __sub__(self, restriction):
         """
         inverted restriction aka antijoin
@@ -212,7 +221,7 @@ def where_clause(self):
             return ''
 
         def make_condition(arg):
-            if isinstance(arg, dict):
+            if isinstance(arg, Mapping):
                 condition = ['`%s`=%s' % (k, repr(v)) for k, v in arg.items() if k in self.heading]
             elif isinstance(arg, np.void):
                 condition = ['`%s`=%s' % (k, arg[k]) for k in arg.dtype.fields if k in self.heading]
@@ -225,20 +234,20 @@ def make_condition(arg):
             negate = isinstance(r, Not)
             if negate:
                 r = r.restriction
-            if isinstance(r, dict) or isinstance(r, np.void):
+            if isinstance(r, Mapping) or isinstance(r, np.void):
                 r = make_condition(r)
             elif isinstance(r, np.ndarray) or isinstance(r, list):
                 r = '(' + ') OR ('.join([make_condition(q) for q in r]) + ')'
             elif isinstance(r, RelationalOperand):
-                common_attributes = ','.join([q for q in self.heading.names if q in r.heading.names])
+                common_attributes = [q for q in self.heading.names if q in r.heading.names]
                 if not common_attributes:
                     r = 'FALSE' if negate else 'TRUE'
                 else:
-                    r = '({fields}) {not_}in (SELECT {fields} FROM {from_}{where})'.format(
+                    common_attributes = '`'+'`,`'.join(common_attributes)+'`'
+                    r = '({fields}) {not_}in ({subquery})'.format(
                         fields=common_attributes,
                         not_="not " if negate else "",
-                        from_=r.from_clause,
-                        where=r.where_clause)
+                        subquery=r.make_select(common_attributes))
                 negate = False
             if not isinstance(r, str):
                 raise DataJointError('Invalid restriction object')
@@ -267,7 +276,8 @@ def __init__(self, arg1, arg2, left=False):
             raise DataJointError('Cannot join relations with different database connections')
         self._arg1 = Subquery(arg1) if arg1.heading.computed else arg1
         self._arg2 = Subquery(arg2) if arg2.heading.computed else arg2
-        self._restrictions = self._arg1.restrictions + self._arg2.restrictions
+        self.restrict(*self._arg1.restrictions)
+        self.restrict(*self._arg2.restrictions)
         self._left = left
         self._heading = self._arg1.heading.join(self._arg2.heading, left=left)
 
@@ -311,12 +321,15 @@ def __init__(self, arg, *attributes, **renamed_attributes):
                 self._renamed_attributes.update({d['alias']: d['sql_expression']})
             else:
                 self._attributes.append(attribute)
+        self._arg = arg
 
-        if arg.heading.computed or arg.restrictions:
+        restricting_on_removed_attributes = bool(
+            arg.attributes_in_restrictions() - set(self.heading.names))
+        use_subquery = restricting_on_removed_attributes or arg.heading.computed
+        if use_subquery:
             self._arg = Subquery(arg)
         else:
-            self._arg = arg
-            self._restrictions = arg.restrictions
+            self.restrict(*arg.restrictions)
 
     def _repr_helper(self):
         return "(%r).project(%r)" % (self._arg, self._attributes)
@@ -329,13 +342,17 @@ def connection(self):
     def heading(self):
         return self._arg.heading.project(*self._attributes, **self._renamed_attributes)
 
+    @property
+    def _grouped(self):
+        return self._arg._grouped
+
     @property
     def from_clause(self):
         return self._arg.from_clause
 
     def __and__(self, restriction):
         """
-        When projection has renamed attributes, it must be enclosed in a subquery before restriction
+        When restricting on renamed attributes, enclose in subquery
         """
         has_restriction = isinstance(restriction, RelationalOperand) or restriction
         do_subquery = has_restriction and self.heading.computed
diff --git a/setup.py b/setup.py
index 112b22ce7..1e95bf956 100644
--- a/setup.py
+++ b/setup.py
@@ -16,7 +16,7 @@
     long_description=long_description,
     author='Dimitri Yatsenko',
     author_email='Dimitri.Yatsenko@gmail.com',
-    license = "GNU LGPL",
+    license="GNU LGPL",
     url='https://github.com/datajoint/datajoint-python',
     keywords='database organization',
     packages=find_packages(exclude=['contrib', 'docs', 'tests*']),
diff --git a/tests/test_fetch.py b/tests/test_fetch.py
index bac9eda77..e4757998c 100644
--- a/tests/test_fetch.py
+++ b/tests/test_fetch.py
@@ -38,10 +38,11 @@ def test_getitem(self):
 
     def test_getitem_for_fetch1(self):
         """Testing Fetch1.__getitem__"""
-        assert_true( (self.subject & "subject_id=10").fetch1['subject_id'] == 10)
-        assert_true( (self.subject & "subject_id=10").fetch1['subject_id','species'] == (10, 'monkey'))
-        assert_true( (self.subject & "subject_id=10").fetch1['subject_id':'species'] == (10, 'Curious George'))
-
+        assert_true((self.subject & "subject_id=10").fetch1['subject_id'] == 10)
+        assert_equal((self.subject & "subject_id=10").fetch1['subject_id', 'species'],
+                     (10, 'monkey'))
+        assert_equal((self.subject & "subject_id=10").fetch1['subject_id':'species'],
+                     (10, 'Curious George'))
 
     def test_order_by(self):
         """Tests order_by sorting order"""
@@ -113,14 +114,14 @@ def test_keys(self):
         langs.sort(key=itemgetter(0), reverse=True)
         langs.sort(key=itemgetter(1), reverse=False)
 
-        cur = self.lang.fetch.order_by('language', 'name DESC')['name','language']
+        cur = self.lang.fetch.order_by('language', 'name DESC')['name', 'language']
         cur2 = list(self.lang.fetch.order_by('language', 'name DESC').keys())
 
         for c, c2 in zip(zip(*cur), cur2):
             assert_true(c == tuple(c2.values()), 'Values are not the same')
 
     def test_fetch1(self):
-        key = {'name': 'Edgar', 'language':'Japanese'}
+        key = {'name': 'Edgar', 'language': 'Japanese'}
         true = schema.Language.contents[-1]
 
         dat = (self.lang & key).fetch1()
@@ -170,7 +171,6 @@ def test_offset(self):
         for c, l in list(zip(cur, langs[1:]))[:4]:
             assert_true(np.all([cc == ll for cc, ll in zip(c, l)]), 'Sorting order is different')
 
-
     def test_limit_warning(self):
         """Tests whether warning is raised if offset is used without limit."""
         with warnings.catch_warnings(record=True) as w: