diff --git a/CHANGELOG.md b/CHANGELOG.md
index d302dc4..a32d9d4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,12 @@
 Change Log
 ==========
 
+v0.9.7
+------
+- Add `distinct` method to querysets
+- Add `AlterTableWithBuffer` migration operation
+- Support Merge engine (M1hacka)
+
 v0.9.6
 ------
 - Fix python3 compatibility (TvoroG)
diff --git a/docs/class_reference.md b/docs/class_reference.md
index 7e4bc74..e56fc7a 100644
--- a/docs/class_reference.md
+++ b/docs/class_reference.md
@@ -7,7 +7,7 @@ infi.clickhouse_orm.database
 ### Database
 
 
-Database instances connect to a specific ClickHouse database for running queries, 
+Database instances connect to a specific ClickHouse database for running queries,
 inserting data and other operations.
 
 #### Database(db_name, db_url="http://localhost:8123/", username=None, password=None, readonly=False, autocreate=True)
@@ -71,7 +71,7 @@ Insert records into the database.
 
 Executes schema migrations.
 
-- `migrations_package_name` - fully qualified name of the Python package 
+- `migrations_package_name` - fully qualified name of the Python package
   containing the migrations.
 - `up_to` - number of the last migration to apply.
 
@@ -89,7 +89,7 @@ Selects records and returns a single page of model instances.
 - `conditions`: optional SQL conditions (contents of the WHERE clause).
 - `settings`: query settings to send as HTTP GET parameters
 
-The result is a namedtuple containing `objects` (list), `number_of_objects`, 
+The result is a namedtuple containing `objects` (list), `number_of_objects`,
 `pages_total`, `number` (of the current page), and `page_size`.
 
 
@@ -128,7 +128,7 @@ infi.clickhouse_orm.models
 
 
 A base class for ORM models. Each model class represent a ClickHouse table. For example:
-    
+
     class CPUStats(Model):
         timestamp = DateTimeField()
         cpu_id = UInt16Field()
@@ -172,7 +172,7 @@ If omitted, it is assumed to be the names of all fields in the model, in order o
 #### get_database()
 
 
-Gets the `Database` that this model instance belongs to. 
+Gets the `Database` that this model instance belongs to.
 Returns `None` unless the instance was read from the database or written to it.
 
 
@@ -191,7 +191,7 @@ Returns a `QuerySet` for selecting instances of this model class.
 #### set_database(db)
 
 
-Sets the `Database` that this model instance belongs to. 
+Sets the `Database` that this model instance belongs to.
 This is done automatically when the instance is read from the database or written to it.
 
 
@@ -261,7 +261,7 @@ If omitted, it is assumed to be the names of all fields in the model, in order o
 #### get_database()
 
 
-Gets the `Database` that this model instance belongs to. 
+Gets the `Database` that this model instance belongs to.
 Returns `None` unless the instance was read from the database or written to it.
 
 
@@ -280,7 +280,7 @@ Returns a `QuerySet` for selecting instances of this model class.
 #### set_database(db)
 
 
-Sets the `Database` that this model instance belongs to. 
+Sets the `Database` that this model instance belongs to.
 This is done automatically when the instance is read from the database or written to it.
 
 
@@ -317,28 +317,28 @@ infi.clickhouse_orm.fields
 
 Abstract base class for all field types.
 
-#### Field(default=None, alias=None, materialized=None)
+#### Field(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### StringField
 
 Extends Field
 
-#### StringField(default=None, alias=None, materialized=None)
+#### StringField(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### DateField
 
 Extends Field
 
-#### DateField(default=None, alias=None, materialized=None)
+#### DateField(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### DateTimeField
 
 Extends Field
 
-#### DateTimeField(default=None, alias=None, materialized=None)
+#### DateTimeField(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### BaseIntField
@@ -348,7 +348,7 @@ Extends Field
 
 Abstract base class for all integer-type fields.
 
-#### BaseIntField(default=None, alias=None, materialized=None)
+#### BaseIntField(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### BaseFloatField
@@ -358,7 +358,7 @@ Extends Field
 
 Abstract base class for all float-type fields.
 
-#### BaseFloatField(default=None, alias=None, materialized=None)
+#### BaseFloatField(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### BaseEnumField
@@ -368,14 +368,14 @@ Extends Field
 
 Abstract base class for all enum-type fields.
 
-#### BaseEnumField(enum_cls, default=None, alias=None, materialized=None)
+#### BaseEnumField(enum_cls, default=None, alias=None, materialized=None, readonly=None)
 
 
 ### ArrayField
 
 Extends Field
 
-#### ArrayField(inner_field, default=None, alias=None, materialized=None)
+#### ArrayField(inner_field, default=None, alias=None, materialized=None, readonly=None)
 
 
 ### NullableField
@@ -389,91 +389,91 @@ Extends Field
 
 Extends StringField
 
-#### FixedStringField(length, default=None, alias=None, materialized=None)
+#### FixedStringField(length, default=None, alias=None, materialized=None, readonly=None)
 
 
 ### UInt8Field
 
 Extends BaseIntField
 
-#### UInt8Field(default=None, alias=None, materialized=None)
+#### UInt8Field(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### UInt16Field
 
 Extends BaseIntField
 
-#### UInt16Field(default=None, alias=None, materialized=None)
+#### UInt16Field(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### UInt32Field
 
 Extends BaseIntField
 
-#### UInt32Field(default=None, alias=None, materialized=None)
+#### UInt32Field(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### UInt64Field
 
 Extends BaseIntField
 
-#### UInt64Field(default=None, alias=None, materialized=None)
+#### UInt64Field(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### Int8Field
 
 Extends BaseIntField
 
-#### Int8Field(default=None, alias=None, materialized=None)
+#### Int8Field(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### Int16Field
 
 Extends BaseIntField
 
-#### Int16Field(default=None, alias=None, materialized=None)
+#### Int16Field(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### Int32Field
 
 Extends BaseIntField
 
-#### Int32Field(default=None, alias=None, materialized=None)
+#### Int32Field(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### Int64Field
 
 Extends BaseIntField
 
-#### Int64Field(default=None, alias=None, materialized=None)
+#### Int64Field(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### Float32Field
 
 Extends BaseFloatField
 
-#### Float32Field(default=None, alias=None, materialized=None)
+#### Float32Field(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### Float64Field
 
 Extends BaseFloatField
 
-#### Float64Field(default=None, alias=None, materialized=None)
+#### Float64Field(default=None, alias=None, materialized=None, readonly=None)
 
 
 ### Enum8Field
 
 Extends BaseEnumField
 
-#### Enum8Field(enum_cls, default=None, alias=None, materialized=None)
+#### Enum8Field(enum_cls, default=None, alias=None, materialized=None, readonly=None)
 
 
 ### Enum16Field
 
 Extends BaseEnumField
 
-#### Enum16Field(enum_cls, default=None, alias=None, materialized=None)
+#### Enum16Field(enum_cls, default=None, alias=None, materialized=None, readonly=None)
 
 
 infi.clickhouse_orm.engines
@@ -512,6 +512,19 @@ Read more [here](https://clickhouse.yandex/reference_en.html#Buffer).
 #### Buffer(main_model, num_layers=16, min_time=10, max_time=100, min_rows=10000, max_rows=1000000, min_bytes=10000000, max_bytes=100000000)
 
 
+### Merge
+
+Extends Engine
+
+
+The Merge engine (not to be confused with MergeTree) does not store data itself,
+but allows reading from any number of other tables simultaneously.
+Writing to a table is not supported
+https://clickhouse.yandex/docs/en/single/index.html#document-table_engines/merge
+
+#### Merge(table_regex)
+
+
 ### CollapsingMergeTree
 
 Extends MergeTree
@@ -585,6 +598,13 @@ Returns the contents of the query's `WHERE` clause as a string.
 Returns the number of matching model instances.
 
 
+#### distinct()
+
+
+Adds a DISTINCT clause to the query, meaning that any duplicate rows
+in the results will be omitted.
+
+
 #### exclude(**kwargs)
 
 
@@ -678,6 +698,13 @@ Returns the contents of the query's `WHERE` clause as a string.
 Returns the number of rows after aggregation.
 
 
+#### distinct()
+
+
+Adds a DISTINCT clause to the query, meaning that any duplicate rows
+in the results will be omitted.
+
+
 #### exclude(**kwargs)
 
 
diff --git a/docs/querysets.md b/docs/querysets.md
index 2bbefd9..d27c836 100644
--- a/docs/querysets.md
+++ b/docs/querysets.md
@@ -99,6 +99,16 @@ When some of the model fields aren't needed, it is more efficient to omit them f
 
     qs = Person.objects_in(database).only('first_name', 'birthday')
 
+Distinct
+--------
+
+Adds a DISTINCT clause to the query, meaning that any duplicate rows in the results will be omitted.
+
+    >>> Person.objects_in(database).only('first_name').count()
+    100
+    >>> Person.objects_in(database).only('first_name').distinct().count()
+    94
+
 Slicing
 -------
 
diff --git a/docs/schema_migrations.md b/docs/schema_migrations.md
index e4647bf..ce56b04 100644
--- a/docs/schema_migrations.md
+++ b/docs/schema_migrations.md
@@ -34,11 +34,13 @@ The following operations are supported:
 
 **CreateTable**
 
-A migration operation that creates a table for a given model class.
+A migration operation that creates a table for a given model class. If the table already exists, the operation does nothing.
+
+In case the model class is a `BufferModel`, the operation first creates the underlying on-disk table, and then creates the buffer table.
 
 **DropTable**
 
-A migration operation that drops the table of a given model class.
+A migration operation that drops the table of a given model class. If the table does not exist, the operation does nothing.
 
 **AlterTable**
 
@@ -50,6 +52,13 @@ A migration operation that compares the table of a given model class to the mode
 
 Default values are not altered by this operation.
 
+**AlterTableWithBuffer**
+
+A compound migration operation for altering a buffer table and its underlying on-disk table. The buffer table is dropped, the on-disk table is altered, and then the buffer table is re-created. This is the procedure recommended in the ClickHouse documentation for handling scenarios in which the underlying table needs to be modified.
+
+Applying this migration operation to a regular table has the same effect as an `AlterTable` operation.
+
+
 Running Migrations
 ------------------
 
diff --git a/docs/table_engines.md b/docs/table_engines.md
index 2f92183..30aa07b 100644
--- a/docs/table_engines.md
+++ b/docs/table_engines.md
@@ -15,6 +15,7 @@ The following engines are supported by the ORM:
 - SummingMergeTree / ReplicatedSummingMergeTree
 - ReplacingMergeTree / ReplicatedReplacingMergeTree
 - Buffer
+- Merge
 
 
 Simple Engines
@@ -85,6 +86,18 @@ Then you can insert objects into Buffer model and they will be handled by ClickH
     suzy = PersonBuffer(first_name='Suzy', last_name='Jones')
     dan = PersonBuffer(first_name='Dan', last_name='Schwartz')
     db.insert([dan, suzy])
+    
+    
+Merge Engine
+-------------
+
+[ClickHouse docs](https://clickhouse.yandex/docs/en/single/index.html#merge)  
+A `Merge` engine is only used in conjunction with a `MergeModel`.   
+This table does not store data itself, but allows reading from any number of other tables simultaneously. So you can't insert in it.
+Engine parameter specifies re2 (similar to PCRE) regular expression, from which data is selected.
+
+    class MergeTable(models.MergeModel):
+        engine = engines.Merge('^table_prefix')
 
 
 ---
diff --git a/docs/toc.md b/docs/toc.md
index aa5bb3b..cc1c8a6 100644
--- a/docs/toc.md
+++ b/docs/toc.md
@@ -20,6 +20,7 @@
       * [Counting and Checking Existence](querysets.md#counting-and-checking-existence)
       * [Ordering](querysets.md#ordering)
       * [Omitting Fields](querysets.md#omitting-fields)
+      * [Distinct](querysets.md#distinct)
       * [Slicing](querysets.md#slicing)
       * [Pagination](querysets.md#pagination)
       * [Aggregation](querysets.md#aggregation)
@@ -36,6 +37,7 @@
       * [Engines in the MergeTree Family](table_engines.md#engines-in-the-mergetree-family)
          * [Data Replication](table_engines.md#data-replication)
       * [Buffer Engine](table_engines.md#buffer-engine)
+      * [Merge Engine](table_engines.md#merge-engine)
 
    * [Schema Migrations](schema_migrations.md#schema-migrations)
       * [Writing Migrations](schema_migrations.md#writing-migrations)
@@ -85,6 +87,7 @@
          * [Memory](class_reference.md#memory)
          * [MergeTree](class_reference.md#mergetree)
          * [Buffer](class_reference.md#buffer)
+         * [Merge](class_reference.md#merge)
          * [CollapsingMergeTree](class_reference.md#collapsingmergetree)
          * [SummingMergeTree](class_reference.md#summingmergetree)
          * [ReplacingMergeTree](class_reference.md#replacingmergetree)
diff --git a/scripts/generate_ref.py b/scripts/generate_ref.py
index c35e881..d2863fd 100644
--- a/scripts/generate_ref.py
+++ b/scripts/generate_ref.py
@@ -51,7 +51,10 @@ def get_method_sig(method):
     for arg in argspec.args:
         default_arg = _get_default_arg(argspec.args, argspec.defaults, arg_index)
         if default_arg.has_default:
-            args.append("%s=%s" % (arg, default_arg.default_value))
+            val = default_arg.default_value
+            if isinstance(val, basestring):
+                val = '"' + val + '"'
+            args.append("%s=%s" % (arg, val))
         else:
             args.append(arg)
         arg_index += 1
diff --git a/src/infi/clickhouse_orm/database.py b/src/infi/clickhouse_orm/database.py
index 5c816d6..4f94b6b 100644
--- a/src/infi/clickhouse_orm/database.py
+++ b/src/infi/clickhouse_orm/database.py
@@ -75,16 +75,16 @@ class Database(object):
         Creates a table for the given model class, if it does not exist already.
         '''
         # TODO check that model has an engine
-        if model_class.readonly:
-            raise DatabaseException("You can't create read only table")
+        if model_class.system:
+            raise DatabaseException("You can't create system table")
         self._send(model_class.create_table_sql(self.db_name))
 
     def drop_table(self, model_class):
         '''
         Drops the database table of the given model class, if it exists.
         '''
-        if model_class.readonly:
-            raise DatabaseException("You can't drop read only table")
+        if model_class.system:
+            raise DatabaseException("You can't drop system table")
         self._send(model_class.drop_table_sql(self.db_name))
 
     def insert(self, model_instances, batch_size=1000):
@@ -103,8 +103,8 @@ class Database(object):
             return  # model_instances is empty
         model_class = first_instance.__class__
 
-        if first_instance.readonly:
-            raise DatabaseException("You can't insert into read only table")
+        if first_instance.readonly or first_instance.system:
+            raise DatabaseException("You can't insert into read only and system tables")
 
         def gen():
             buf = BytesIO()
diff --git a/src/infi/clickhouse_orm/engines.py b/src/infi/clickhouse_orm/engines.py
index caa05c7..777bd2e 100644
--- a/src/infi/clickhouse_orm/engines.py
+++ b/src/infi/clickhouse_orm/engines.py
@@ -1,4 +1,7 @@
 from __future__ import unicode_literals
+
+import six
+
 from .utils import comma_join
 
 
@@ -118,7 +121,6 @@ class Buffer(Engine):
         self.min_bytes = min_bytes
         self.max_bytes = max_bytes
 
-
     def create_table_sql(self, db_name):
         # Overriden create_table_sql example:
         #sql = 'ENGINE = Buffer(merge, hits, 16, 10, 100, 10000, 1000000, 10000000, 100000000)'
@@ -128,3 +130,27 @@ class Buffer(Engine):
                    self.max_rows, self.min_bytes, self.max_bytes
               )
         return sql
+
+
+class Merge(Engine):
+    """
+    The Merge engine (not to be confused with MergeTree) does not store data itself,
+    but allows reading from any number of other tables simultaneously.
+    Writing to a table is not supported
+    https://clickhouse.yandex/docs/en/single/index.html#document-table_engines/merge
+    """
+
+    def __init__(self, table_regex):
+        assert isinstance(table_regex, six.string_types), "'table_regex' parameter must be string"
+
+        self.table_regex = table_regex
+
+        # Use current database as default
+        self.db_name = 'currentDatabase()'
+
+    def create_table_sql(self):
+        return "Merge(%s, '%s')" % (self.db_name, self.table_regex)
+
+    def set_db_name(self, db_name):
+        assert isinstance(db_name, six.string_types), "'db_name' parameter must be string"
+        self.db_name = db_name
diff --git a/src/infi/clickhouse_orm/fields.py b/src/infi/clickhouse_orm/fields.py
index a57314e..3e3207a 100644
--- a/src/infi/clickhouse_orm/fields.py
+++ b/src/infi/clickhouse_orm/fields.py
@@ -16,19 +16,21 @@ class Field(object):
     class_default = 0
     db_type = None
 
-    def __init__(self, default=None, alias=None, materialized=None):
+    def __init__(self, default=None, alias=None, materialized=None, readonly=None):
         assert (None, None) in {(default, alias), (alias, materialized), (default, materialized)}, \
             "Only one of default, alias and materialized parameters can be given"
         assert alias is None or isinstance(alias, string_types) and alias != "",\
             "Alias field must be string field name, if given"
         assert materialized is None or isinstance(materialized, string_types) and alias != "",\
             "Materialized field must be string, if given"
+        assert readonly is None or type(readonly) is bool, "readonly parameter must be bool if given"
 
         self.creation_counter = Field.creation_counter
         Field.creation_counter += 1
         self.default = self.class_default if default is None else default
         self.alias = alias
         self.materialized = materialized
+        self.readonly = bool(self.alias or self.materialized or readonly)
 
     def to_python(self, value, timezone_in_use):
         '''
@@ -75,10 +77,6 @@ class Field(object):
         else:
             return self.db_type
 
-    @property
-    def readonly(self):
-        return bool(self.alias or self.materialized)
-
 
 class StringField(Field):
 
@@ -95,10 +93,10 @@ class StringField(Field):
 
 class FixedStringField(StringField):
 
-    def __init__(self, length, default=None, alias=None, materialized=None):
+    def __init__(self, length, default=None, alias=None, materialized=None, readonly=None):
         self._length = length
         self.db_type = 'FixedString(%d)' % length
-        super(FixedStringField, self).__init__(default, alias, materialized)
+        super(FixedStringField, self).__init__(default, alias, materialized, readonly)
 
     def to_python(self, value, timezone_in_use):
         value = super(FixedStringField, self).to_python(value, timezone_in_use)
@@ -274,11 +272,11 @@ class BaseEnumField(Field):
     Abstract base class for all enum-type fields.
     '''
 
-    def __init__(self, enum_cls, default=None, alias=None, materialized=None):
+    def __init__(self, enum_cls, default=None, alias=None, materialized=None, readonly=None):
         self.enum_cls = enum_cls
         if default is None:
             default = list(enum_cls)[0]
-        super(BaseEnumField, self).__init__(default, alias, materialized)
+        super(BaseEnumField, self).__init__(default, alias, materialized, readonly)
 
     def to_python(self, value, timezone_in_use):
         if isinstance(value, self.enum_cls):
@@ -338,9 +336,9 @@ class ArrayField(Field):
 
     class_default = []
 
-    def __init__(self, inner_field, default=None, alias=None, materialized=None):
+    def __init__(self, inner_field, default=None, alias=None, materialized=None, readonly=None):
         self.inner_field = inner_field
-        super(ArrayField, self).__init__(default, alias, materialized)
+        super(ArrayField, self).__init__(default, alias, materialized, readonly)
 
     def to_python(self, value, timezone_in_use):
         if isinstance(value, text_type):
@@ -374,7 +372,7 @@ class NullableField(Field):
         self._null_values = [None]
         if extra_null_values:
             self._null_values.extend(extra_null_values)
-        super(NullableField, self).__init__(default, alias, materialized)
+        super(NullableField, self).__init__(default, alias, materialized, readonly=None)
 
     def to_python(self, value, timezone_in_use):
         if value == '\\N' or value is None:
diff --git a/src/infi/clickhouse_orm/migrations.py b/src/infi/clickhouse_orm/migrations.py
index 1a82a5b..a7843a7 100644
--- a/src/infi/clickhouse_orm/migrations.py
+++ b/src/infi/clickhouse_orm/migrations.py
@@ -82,6 +82,25 @@ class AlterTable(Operation):
                 self._alter_table(database, 'MODIFY COLUMN %s %s' % model_field)
 
 
+class AlterTableWithBuffer(Operation):
+    '''
+    A migration operation for altering a buffer table and its underlying on-disk table.
+    The buffer table is dropped, the on-disk table is altered, and then the buffer table
+    is re-created.
+    '''
+
+    def __init__(self, model_class):
+        self.model_class = model_class
+
+    def apply(self, database):
+        if issubclass(self.model_class, BufferModel):
+            DropTable(self.model_class).apply(database)
+            AlterTable(self.model_class.engine.main_model).apply(database)
+            CreateTable(self.model_class).apply(database)
+        else:
+            AlterTable(self.model_class).apply(database)
+
+
 class DropTable(Operation):
     '''
     A migration operation that drops the table of a given model class.
@@ -91,7 +110,7 @@ class DropTable(Operation):
         self.model_class = model_class
 
     def apply(self, database):
-        logger.info('    Drop table %s', self.model_class.__name__)
+        logger.info('    Drop table %s', self.model_class.table_name())
         database.drop_table(self.model_class)
 
 
diff --git a/src/infi/clickhouse_orm/models.py b/src/infi/clickhouse_orm/models.py
index 8714447..33cfde2 100644
--- a/src/infi/clickhouse_orm/models.py
+++ b/src/infi/clickhouse_orm/models.py
@@ -4,9 +4,10 @@ from logging import getLogger
 from six import with_metaclass
 import pytz
 
-from .fields import Field
+from .fields import Field, StringField
 from .utils import parse_tsv
 from .query import QuerySet
+from .engines import Merge
 
 logger = getLogger('clickhouse_orm')
 
@@ -86,8 +87,13 @@ class Model(with_metaclass(ModelBase)):
     '''
 
     engine = None
+
+    # Insert operations are restricted for read only models
     readonly = False
 
+    # Create table, drop table, insert operations are restricted for system models
+    system = False
+
     def __init__(self, **kwargs):
         '''
         Creates a model instance, using keyword arguments as field values.
@@ -246,3 +252,25 @@ class BufferModel(Model):
         engine_str = cls.engine.create_table_sql(db_name)
         parts.append(engine_str)
         return ' '.join(parts)
+
+
+class MergeModel(Model):
+    '''
+    Model for Merge engine
+    Predefines virtual _table column an controls that rows can't be inserted to this table type
+    https://clickhouse.yandex/docs/en/single/index.html#document-table_engines/merge
+    '''
+    readonly = True
+
+    # Virtual fields can't be inserted into database
+    _table = StringField(readonly=True)
+
+    def set_database(self, db):
+        '''
+        Gets the `Database` that this model instance belongs to.
+        Returns `None` unless the instance was read from the database or written to it.
+        '''
+        assert isinstance(self.engine, Merge), "engine must be engines.Merge instance"
+        res = super(MergeModel, self).set_database(db)
+        self.engine.set_db_name(db.db_name)
+        return res
diff --git a/src/infi/clickhouse_orm/query.py b/src/infi/clickhouse_orm/query.py
index c1c1dd0..0bf764a 100644
--- a/src/infi/clickhouse_orm/query.py
+++ b/src/infi/clickhouse_orm/query.py
@@ -187,6 +187,7 @@ class QuerySet(object):
         self._q = []
         self._fields = []
         self._limits = None
+        self._distinct = False
 
     def __iter__(self):
         """
@@ -228,14 +229,15 @@ class QuerySet(object):
         """
         Returns the whole query as a SQL string.
         """
+        distinct = 'DISTINCT ' if self._distinct else ''
         fields = '*'
         if self._fields:
             fields = comma_join('`%s`' % field for field in self._fields)
         ordering = '\nORDER BY ' + self.order_by_as_sql() if self._order_by else ''
         limit = '\nLIMIT %d, %d' % self._limits if self._limits else ''
-        params = (fields, self._model_cls.table_name(),
+        params = (distinct, fields, self._model_cls.table_name(),
                   self.conditions_as_sql(), ordering, limit)
-        return u'SELECT %s\nFROM `%s`\nWHERE %s%s%s' % params
+        return u'SELECT %s%s\nFROM `%s`\nWHERE %s%s%s' % params
 
     def order_by_as_sql(self):
         """
@@ -259,6 +261,11 @@ class QuerySet(object):
         """
         Returns the number of matching model instances.
         """
+        if self._distinct:
+            # Use a subquery, since a simple count won't be accurate
+            sql = u'SELECT count() FROM (%s)' % self.as_sql()
+            raw = self._database.raw(sql)
+            return int(raw) if raw else 0
         return self._database.count(self._model_cls, self.conditions_as_sql())
 
     def order_by(self, *field_names):
@@ -296,7 +303,7 @@ class QuerySet(object):
         return qs
 
     def paginate(self, page_num=1, page_size=100):
-        '''
+        """
         Returns a single page of model instances that match the queryset.
         Note that `order_by` should be used first, to ensure a correct
         partitioning of records into pages.
@@ -306,7 +313,7 @@ class QuerySet(object):
 
         The result is a namedtuple containing `objects` (list), `number_of_objects`,
         `pages_total`, `number` (of the current page), and `page_size`.
-        '''
+        """
         from .database import Page
         count = self.count()
         pages_total = int(ceil(count / float(page_size)))
@@ -323,8 +330,17 @@ class QuerySet(object):
             page_size=page_size
         )
 
+    def distinct(self):
+        """
+        Adds a DISTINCT clause to the query, meaning that any duplicate rows
+        in the results will be omitted.
+        """
+        qs = copy(self)
+        qs._distinct = True
+        return qs
+
     def aggregate(self, *args, **kwargs):
-        '''
+        """
         Returns an `AggregateQuerySet` over this query, with `args` serving as
         grouping fields and `kwargs` serving as calculated fields. At least one
         calculated field is required. For example:
@@ -337,7 +353,7 @@ class QuerySet(object):
             WHERE data > '2017-08-01'
             GROUP BY event_type
         ```
-        '''
+        """
         return AggregateQuerySet(self, args, kwargs)
 
 
@@ -368,6 +384,7 @@ class AggregateQuerySet(QuerySet):
         self._order_by = list(base_qs._order_by)
         self._q = list(base_qs._q)
         self._limits = base_qs._limits
+        self._distinct = base_qs._distinct
 
     def group_by(self, *args):
         """
@@ -398,15 +415,17 @@ class AggregateQuerySet(QuerySet):
         """
         Returns the whole query as a SQL string.
         """
+        distinct = 'DISTINCT ' if self._distinct else ''
         grouping = comma_join('`%s`' % field for field in self._grouping_fields)
         fields = comma_join(list(self._fields) + ['%s AS %s' % (v, k) for k, v in self._calculated_fields.items()])
         params = dict(
+            distinct=distinct,
             grouping=grouping or "''",
             fields=fields,
             table=self._model_cls.table_name(),
             conds=self.conditions_as_sql()
         )
-        sql = u'SELECT %(fields)s\nFROM `%(table)s`\nWHERE %(conds)s\nGROUP BY %(grouping)s' % params
+        sql = u'SELECT %(distinct)s%(fields)s\nFROM `%(table)s`\nWHERE %(conds)s\nGROUP BY %(grouping)s' % params
         if self._order_by:
             sql += '\nORDER BY ' + self.order_by_as_sql()
         if self._limits:
diff --git a/src/infi/clickhouse_orm/system_models.py b/src/infi/clickhouse_orm/system_models.py
index 49247d9..5ca3efd 100644
--- a/src/infi/clickhouse_orm/system_models.py
+++ b/src/infi/clickhouse_orm/system_models.py
@@ -20,6 +20,7 @@ class SystemPart(Model):
     OPERATIONS = frozenset({'DETACH', 'DROP', 'ATTACH', 'FREEZE', 'FETCH'})
 
     readonly = True
+    system = True
 
     database = StringField()  # Name of the database where the table that this part belongs to is located.
     table = StringField()  # Name of the table that this part belongs to.
@@ -27,6 +28,10 @@ class SystemPart(Model):
     partition = StringField()  # Name of the partition, in the format YYYYMM.
     name = StringField()  # Name of the part.
 
+    # This field is present in the docs (https://clickhouse.yandex/docs/en/single/index.html#system-parts),
+    # but is absent in ClickHouse (in version 1.1.54245)
+    # replicated = UInt8Field()  # Whether the part belongs to replicated data.
+
     # Whether the part is used in a table, or is no longer needed and will be deleted soon.
     # Inactive parts remain after merging.
     active = UInt8Field()
diff --git a/tests/sample_migrations/0010.py b/tests/sample_migrations/0010.py
new file mode 100644
index 0000000..3892583
--- /dev/null
+++ b/tests/sample_migrations/0010.py
@@ -0,0 +1,6 @@
+from infi.clickhouse_orm import migrations
+from ..test_migrations import *
+
+operations = [
+    migrations.CreateTable(Model4Buffer)
+]
diff --git a/tests/sample_migrations/0011.py b/tests/sample_migrations/0011.py
new file mode 100644
index 0000000..dd9d09e
--- /dev/null
+++ b/tests/sample_migrations/0011.py
@@ -0,0 +1,6 @@
+from infi.clickhouse_orm import migrations
+from ..test_migrations import *
+
+operations = [
+    migrations.AlterTableWithBuffer(Model4Buffer_changed)
+]
diff --git a/tests/test_engines.py b/tests/test_engines.py
index ddc3a85..65497ca 100644
--- a/tests/test_engines.py
+++ b/tests/test_engines.py
@@ -2,7 +2,7 @@ from __future__ import unicode_literals
 import unittest
 
 from infi.clickhouse_orm.database import Database, DatabaseException
-from infi.clickhouse_orm.models import Model
+from infi.clickhouse_orm.models import Model, MergeModel
 from infi.clickhouse_orm.fields import *
 from infi.clickhouse_orm.engines import *
 
@@ -74,6 +74,56 @@ class EnginesTestCase(unittest.TestCase):
             engine = Memory()
         self._create_and_insert(TestModel)
 
+    def test_merge(self):
+        class TestModel1(SampleModel):
+            engine = TinyLog()
+
+        class TestModel2(SampleModel):
+            engine = TinyLog()
+
+        class TestMergeModel(MergeModel, SampleModel):
+            engine = Merge('^testmodel')
+
+        self.database.create_table(TestModel1)
+        self.database.create_table(TestModel2)
+        self.database.create_table(TestMergeModel)
+
+        # Insert operations are restricted for this model type
+        with self.assertRaises(DatabaseException):
+            self.database.insert([
+                TestMergeModel(date='2017-01-01', event_id=23423, event_group=13, event_count=7, event_version=1)
+            ])
+
+        # Testing select
+        self.database.insert([
+            TestModel1(date='2017-01-01', event_id=1, event_group=1, event_count=1, event_version=1)
+        ])
+        self.database.insert([
+            TestModel2(date='2017-01-02', event_id=2, event_group=2, event_count=2, event_version=2)
+        ])
+        # event_uversion is materialized field. So * won't select it and it will be zero
+        res = self.database.select('SELECT *, event_uversion FROM $table ORDER BY event_id', model_class=TestMergeModel)
+        res = [row for row in res]
+        self.assertEqual(2, len(res))
+        self.assertDictEqual({
+            '_table': 'testmodel1',
+            'date': datetime.date(2017, 1, 1),
+            'event_id': 1,
+            'event_group': 1,
+            'event_count': 1,
+            'event_version': 1,
+            'event_uversion': 1
+        }, res[0].to_dict(include_readonly=True))
+        self.assertDictEqual({
+            '_table': 'testmodel2',
+            'date': datetime.date(2017, 1, 2),
+            'event_id': 2,
+            'event_group': 2,
+            'event_count': 2,
+            'event_version': 2,
+            'event_uversion': 2
+        }, res[1].to_dict(include_readonly=True))
+
 
 class SampleModel(Model):
 
diff --git a/tests/test_migrations.py b/tests/test_migrations.py
index 3478f9f..7e31c84 100644
--- a/tests/test_migrations.py
+++ b/tests/test_migrations.py
@@ -2,7 +2,7 @@ from __future__ import unicode_literals
 import unittest
 
 from infi.clickhouse_orm.database import Database
-from infi.clickhouse_orm.models import Model
+from infi.clickhouse_orm.models import Model, BufferModel
 from infi.clickhouse_orm.fields import *
 from infi.clickhouse_orm.engines import *
 from infi.clickhouse_orm.migrations import MigrationHistory
@@ -61,6 +61,7 @@ class MigrationsTestCase(unittest.TestCase):
         self.assertTrue(self.tableExists(EnumModel1))
         self.assertEquals(self.getTableFields(EnumModel2),
                           [('date', 'Date'), ('f1', "Enum16('dog' = 1, 'cat' = 2, 'horse' = 3, 'pig' = 4)")])
+        # Materialized fields and alias fields
         self.database.migrate('tests.sample_migrations', 8)
         self.assertTrue(self.tableExists(MaterializedModel))
         self.assertEquals(self.getTableFields(MaterializedModel),
@@ -69,6 +70,15 @@ class MigrationsTestCase(unittest.TestCase):
         self.assertTrue(self.tableExists(AliasModel))
         self.assertEquals(self.getTableFields(AliasModel),
                           [('date', 'Date'), ('date_alias', "Date")])
+        # Buffer models creation and alteration
+        self.database.migrate('tests.sample_migrations', 10)
+        self.assertTrue(self.tableExists(Model4))
+        self.assertTrue(self.tableExists(Model4Buffer))
+        self.assertEquals(self.getTableFields(Model4), [('date', 'Date'), ('f1', 'Int32'), ('f2', 'String')])
+        self.assertEquals(self.getTableFields(Model4Buffer), [('date', 'Date'), ('f1', 'Int32'), ('f2', 'String')])
+        self.database.migrate('tests.sample_migrations', 11)
+        self.assertEquals(self.getTableFields(Model4), [('date', 'Date'), ('f3', 'DateTime'), ('f2', 'String')])
+        self.assertEquals(self.getTableFields(Model4Buffer), [('date', 'Date'), ('f3', 'DateTime'), ('f2', 'String')])
 
 
 # Several different models with the same table name, to simulate a table that changes over time
@@ -159,3 +169,47 @@ class AliasModel(Model):
     @classmethod
     def table_name(cls):
         return 'alias_date'
+
+
+class Model4(Model):
+
+    date = DateField()
+    f1 = Int32Field()
+    f2 = StringField()
+
+    engine = MergeTree('date', ('date',))
+
+    @classmethod
+    def table_name(cls):
+        return 'model4'
+
+
+class Model4Buffer(BufferModel, Model4):
+
+    engine = Buffer(Model4)
+
+    @classmethod
+    def table_name(cls):
+        return 'model4buffer'
+
+
+class Model4_changed(Model):
+
+    date = DateField()
+    f3 = DateTimeField()
+    f2 = StringField()
+
+    engine = MergeTree('date', ('date',))
+
+    @classmethod
+    def table_name(cls):
+        return 'model4'
+
+
+class Model4Buffer_changed(BufferModel, Model4_changed):
+
+    engine = Buffer(Model4_changed)
+
+    @classmethod
+    def table_name(cls):
+        return 'model4buffer'
diff --git a/tests/test_querysets.py b/tests/test_querysets.py
index ad834bb..cbbc65d 100644
--- a/tests/test_querysets.py
+++ b/tests/test_querysets.py
@@ -21,8 +21,11 @@ class QuerySetTestCase(TestCaseWithData):
 
     def _test_qs(self, qs, expected_count):
         logging.info(qs.as_sql())
+        count = 0
         for instance in qs:
-            logging.info('\t%s' % instance.to_dict())
+            count += 1
+            logging.info('\t[%d]\t%s' % (count, instance.to_dict()))
+        self.assertEquals(count, expected_count)
         self.assertEquals(qs.count(), expected_count)
 
     def test_no_filtering(self):
@@ -202,6 +205,11 @@ class QuerySetTestCase(TestCaseWithData):
         page = qs.paginate(1, 100)
         self.assertEquals(page.number_of_objects, 10)
 
+    def test_distinct(self):
+        qs = Person.objects_in(self.database).distinct()
+        self._test_qs(qs, 100)
+        self._test_qs(qs.only('first_name'), 94)
+
 
 class AggregateTestCase(TestCaseWithData):
 
@@ -310,6 +318,12 @@ class AggregateTestCase(TestCaseWithData):
             qs = qs.filter(weekday=1)
             self.assertEquals(qs.count(), 1)
 
+    def test_aggregate_with_distinct(self):
+        # In this case distinct has no effect
+        qs = Person.objects_in(self.database).aggregate(average_height='avg(height)').distinct()
+        print(qs.as_sql())
+        self.assertEquals(qs.count(), 1)
+
 
 Color = Enum('Color', u'red blue green yellow brown white black')
 
diff --git a/tests/test_readonly.py b/tests/test_readonly.py
index ae3d54f..facbaa0 100644
--- a/tests/test_readonly.py
+++ b/tests/test_readonly.py
@@ -1,12 +1,7 @@
 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
-import unittest
 
-import six
-from infi.clickhouse_orm.database import Database, DatabaseException
-from infi.clickhouse_orm.models import Model
-from infi.clickhouse_orm.fields import *
-from infi.clickhouse_orm.engines import *
+from infi.clickhouse_orm.database import DatabaseException
 from .base_test_with_data import *
 
 
@@ -45,15 +40,15 @@ class ReadonlyTestCase(TestCaseWithData):
             self.database.insert([m])
 
     def test_create_readonly_table(self):
-        with self.assertRaises(DatabaseException):
-            self.database.create_table(ReadOnlyModel)
+        self.database.create_table(ReadOnlyModel)
 
     def test_drop_readonly_table(self):
-        with self.assertRaises(DatabaseException):
-            self.database.drop_table(ReadOnlyModel)
+        self.database.drop_table(ReadOnlyModel)
 
 
 class ReadOnlyModel(Model):
     readonly = True
 
     name = StringField()
+    date = DateField()
+    engine = MergeTree('date', ('name',))
diff --git a/tests/test_system_models.py b/tests/test_system_models.py
index 1a3b49a..54b6650 100644
--- a/tests/test_system_models.py
+++ b/tests/test_system_models.py
@@ -2,14 +2,34 @@ from __future__ import unicode_literals
 import unittest
 from datetime import date
 import os
-import shutil
-from infi.clickhouse_orm.database import Database
+from infi.clickhouse_orm.database import Database, DatabaseException
 from infi.clickhouse_orm.engines import *
 from infi.clickhouse_orm.fields import *
 from infi.clickhouse_orm.models import Model
 from infi.clickhouse_orm.system_models import SystemPart
 
 
+class SystemTest(unittest.TestCase):
+    def setUp(self):
+        self.database = Database('test-db')
+
+    def tearDown(self):
+        self.database.drop_database()
+
+    def test_insert_system(self):
+        m = SystemPart()
+        with self.assertRaises(DatabaseException):
+            self.database.insert([m])
+
+    def test_create_readonly_table(self):
+        with self.assertRaises(DatabaseException):
+            self.database.create_table(SystemTestModel)
+
+    def test_drop_readonly_table(self):
+        with self.assertRaises(DatabaseException):
+            self.database.drop_table(SystemTestModel)
+
+
 class SystemPartTest(unittest.TestCase):
 
     BACKUP_DIRS = ['/var/lib/clickhouse/shadow', '/opt/clickhouse/shadow/']
@@ -75,3 +95,7 @@ class TestTable(Model):
     date_field = DateField()
 
     engine = MergeTree('date_field', ('date_field',))
+
+
+class SystemTestModel(Model):
+    system = True