16 files changed, 212 insertions, 89 deletions

diff --git a/src/mailman/database/alembic/versions/2bb9b382198_workflow_state_table.py b/src/mailman/database/alembic/versions/2bb9b382198_workflow_state_table.py
index 64def0253..df7a10e00 100644
--- a/src/mailman/database/alembic/versions/2bb9b382198_workflow_state_table.py
+++ b/src/mailman/database/alembic/versions/2bb9b382198_workflow_state_table.py
@@ -9,6 +9,7 @@ Create Date: 2015-03-25 18:09:18.338790
 import sqlalchemy as sa
 
 from alembic import op
+from mailman.database.types import SAUnicode
 
 
 # Revision identifiers, used by Alembic.
@@ -19,10 +20,10 @@ down_revision = '16c2b25c7b'
 def upgrade():
     op.create_table(
         'workflowstate',
-        sa.Column('name', sa.Unicode(), nullable=False),
-        sa.Column('token', sa.Unicode(), nullable=False),
-        sa.Column('step', sa.Unicode(), nullable=True),
-        sa.Column('data', sa.Unicode(), nullable=True),
+        sa.Column('name', SAUnicode(), nullable=False),
+        sa.Column('token', SAUnicode(), nullable=False),
+        sa.Column('step', SAUnicode(), nullable=True),
+        sa.Column('data', SAUnicode(), nullable=True),
         sa.PrimaryKeyConstraint('name', 'token')
         )
 
diff --git a/src/mailman/database/alembic/versions/33bc0099223_add_member_indexes.py b/src/mailman/database/alembic/versions/33bc0099223_add_member_indexes.py
index ce8f2f3f1..5f01f4a66 100644
--- a/src/mailman/database/alembic/versions/33bc0099223_add_member_indexes.py
+++ b/src/mailman/database/alembic/versions/33bc0099223_add_member_indexes.py
@@ -7,6 +7,7 @@ Create Date: 2015-11-19 23:04:42.449553
 """
 
 from alembic import op
+from mailman.database.helpers import is_mysql
 
 
 # Revision identifiers, used by Alembic.
@@ -15,22 +16,28 @@ down_revision = '42756496720'
 
 
 def upgrade():
-    op.create_index(op.f('ix_member_address_id'),
-                    'member', ['address_id'],
-                    unique=False)
-    op.create_index(op.f('ix_member_preferences_id'),
-                    'member', ['preferences_id'],
-                    unique=False)
-    op.create_index(op.f('ix_member_user_id'),
-                    'member', ['user_id'],
-                    unique=False)
     op.create_index(op.f('ix_address_email'),
                     'address', ['email'],
                     unique=False)
+    # MySQL automatically creates the indexes for primary keys so don't need
+    # to do it explicitly again.
+    if not is_mysql(op.get_bind()):
+        op.create_index(op.f('ix_member_address_id'),
+                        'member', ['address_id'],
+                        unique=False)
+        op.create_index(op.f('ix_member_preferences_id'),
+                        'member', ['preferences_id'],
+                        unique=False)
+        op.create_index(op.f('ix_member_user_id'),
+                        'member', ['user_id'],
+                        unique=False)
 
 
 def downgrade():
     op.drop_index(op.f('ix_address_email'), table_name='address')
-    op.drop_index(op.f('ix_member_user_id'), table_name='member')
-    op.drop_index(op.f('ix_member_preferences_id'), table_name='member')
-    op.drop_index(op.f('ix_member_address_id'), table_name='member')
+    # MySQL automatically creates and removes the indexes for primary keys.
+    # So, you cannot drop it without removing the foreign key constraint.
+    if not is_mysql(op.get_bind()):
+        op.drop_index(op.f('ix_member_user_id'), table_name='member')
+        op.drop_index(op.f('ix_member_preferences_id'), table_name='member')
+        op.drop_index(op.f('ix_member_address_id'), table_name='member')
diff --git a/src/mailman/database/alembic/versions/33e1f5f6fa8_.py b/src/mailman/database/alembic/versions/33e1f5f6fa8_.py
index a8b572518..72754d3c5 100644
--- a/src/mailman/database/alembic/versions/33e1f5f6fa8_.py
+++ b/src/mailman/database/alembic/versions/33e1f5f6fa8_.py
@@ -29,6 +29,7 @@ import sqlalchemy as sa
 
 from alembic import op
 from mailman.database.helpers import is_sqlite
+from mailman.database.types import SAUnicode
 
 
 # Revision identifiers, used by Alembic.
@@ -50,7 +51,7 @@ def upgrade():
         # SQLite does not support altering columns.
         return
     for table, column in COLUMNS_TO_CHANGE:
-        op.alter_column(table, column, type_=sa.Unicode)
+        op.alter_column(table, column, type_=SAUnicode)
 
 
 def downgrade():
diff --git a/src/mailman/database/alembic/versions/42756496720_header_matches.py b/src/mailman/database/alembic/versions/42756496720_header_matches.py
index 4514fb398..d1308a134 100644
--- a/src/mailman/database/alembic/versions/42756496720_header_matches.py
+++ b/src/mailman/database/alembic/versions/42756496720_header_matches.py
@@ -10,7 +10,7 @@ import sqlalchemy as sa
 
 from alembic import op
 from mailman.database.helpers import exists_in_db, is_sqlite
-
+from mailman.database.types import SAUnicode
 
 # Revision identifiers, used by Alembic.
 revision = '42756496720'
@@ -23,9 +23,9 @@ def upgrade():
         'headermatch',
         sa.Column('id', sa.Integer(), nullable=False),
         sa.Column('mailing_list_id', sa.Integer(), nullable=True),
-        sa.Column('header', sa.Unicode(), nullable=False),
-        sa.Column('pattern', sa.Unicode(), nullable=False),
-        sa.Column('chain', sa.Unicode(), nullable=True),
+        sa.Column('header', SAUnicode(), nullable=False),
+        sa.Column('pattern', SAUnicode(), nullable=False),
+        sa.Column('chain', SAUnicode(), nullable=True),
         sa.ForeignKeyConstraint(['mailing_list_id'], ['mailinglist.id'], ),
         sa.PrimaryKeyConstraint('id')
         )
@@ -73,8 +73,8 @@ def downgrade():
     header_match_table = sa.sql.table(
         'headermatch',
         sa.sql.column('mailing_list_id', sa.Integer),
-        sa.sql.column('header', sa.Unicode),
-        sa.sql.column('pattern', sa.Unicode),
+        sa.sql.column('header', SAUnicode),
+        sa.sql.column('pattern', SAUnicode),
         )
     for mlist_id, header, pattern in connection.execute(
             header_match_table.select()).fetchall():
diff --git a/src/mailman/database/alembic/versions/46e92facee7_add_serverowner_domainowner.py b/src/mailman/database/alembic/versions/46e92facee7_add_serverowner_domainowner.py
index 1c689670a..bf734934b 100644
--- a/src/mailman/database/alembic/versions/46e92facee7_add_serverowner_domainowner.py
+++ b/src/mailman/database/alembic/versions/46e92facee7_add_serverowner_domainowner.py
@@ -56,8 +56,9 @@ def downgrade():
     if not is_sqlite(op.get_bind()):
         op.drop_column('user', 'is_server_owner')
     if not exists_in_db(op.get_bind(), 'domain', 'contact_address'):
-        # SQLite may not have removed it.
+        # SQLite may not have removed it.  Add a fixed length VARCHAR for
+        # MySQL.
         op.add_column(
             'domain',
-            sa.Column('contact_address', sa.VARCHAR(), nullable=True))
+            sa.Column('contact_address', sa.VARCHAR(255), nullable=True))
     op.drop_table('domain_owner')
diff --git a/src/mailman/database/alembic/versions/47294d3a604_pendable_indexes.py b/src/mailman/database/alembic/versions/47294d3a604_pendable_indexes.py
index 5e465af24..4aafb4613 100644
--- a/src/mailman/database/alembic/versions/47294d3a604_pendable_indexes.py
+++ b/src/mailman/database/alembic/versions/47294d3a604_pendable_indexes.py
@@ -13,6 +13,7 @@ import json
 import sqlalchemy as sa
 
 from alembic import op
+from mailman.database.types import SAUnicode
 
 
 # revision identifiers, used by Alembic.
@@ -34,8 +35,8 @@ pended_table = sa.sql.table(
 keyvalue_table = sa.sql.table(
     'pendedkeyvalue',
     sa.sql.column('id', sa.Integer),
-    sa.sql.column('key', sa.Unicode),
-    sa.sql.column('value', sa.Unicode),
+    sa.sql.column('key', SAUnicode),
+    sa.sql.column('value', SAUnicode),
     sa.sql.column('pended_id', sa.Integer),
     )
 
diff --git a/src/mailman/database/alembic/versions/70af5a4e5790_digests.py b/src/mailman/database/alembic/versions/70af5a4e5790_digests.py
index 50c87ccf3..1f9a93bcd 100644
--- a/src/mailman/database/alembic/versions/70af5a4e5790_digests.py
+++ b/src/mailman/database/alembic/versions/70af5a4e5790_digests.py
@@ -20,7 +20,10 @@ down_revision = '47294d3a604'
 
 def upgrade():
     with op.batch_alter_table('mailinglist') as batch_op:
-        batch_op.alter_column('digestable', new_column_name='digests_enabled')
+        batch_op.alter_column('digestable',
+                              new_column_name='digests_enabled',
+                              existing_type=sa.Boolean)
+        # All column modifications require existing types for Mysql.
         batch_op.drop_column('nondigestable')
     # Non-database migration: rename the list's data-path.
     for dirname in os.listdir(config.LIST_DATA_DIR):
@@ -34,7 +37,9 @@ def upgrade():
 
 def downgrade():
     with op.batch_alter_table('mailinglist') as batch_op:
-        batch_op.alter_column('digests_enabled', new_column_name='digestable')
+        batch_op.alter_column('digests_enabled',
+                              new_column_name='digestable',
+                              existing_type=sa.Boolean)
         # The data for this column is lost, it's not used anyway.
         batch_op.add_column(sa.Column('nondigestable', sa.Boolean))
     for dirname in os.listdir(config.LIST_DATA_DIR):
diff --git a/src/mailman/database/alembic/versions/7b254d88f122_members_and_list_moderation_action.py b/src/mailman/database/alembic/versions/7b254d88f122_members_and_list_moderation_action.py
index 6b4d7bfd1..9f19e3278 100644
--- a/src/mailman/database/alembic/versions/7b254d88f122_members_and_list_moderation_action.py
+++ b/src/mailman/database/alembic/versions/7b254d88f122_members_and_list_moderation_action.py
@@ -13,7 +13,7 @@ fallback to the list's default.
 import sqlalchemy as sa
 
 from alembic import op
-from mailman.database.types import Enum
+from mailman.database.types import Enum, SAUnicode
 from mailman.interfaces.action import Action
 from mailman.interfaces.member import MemberRole
 
@@ -26,7 +26,7 @@ down_revision = 'd4fbb4fd34ca'
 mailinglist_table = sa.sql.table(
     'mailinglist',
     sa.sql.column('id', sa.Integer),
-    sa.sql.column('list_id', sa.Unicode),
+    sa.sql.column('list_id', SAUnicode),
     sa.sql.column('default_member_action', Enum(Action)),
     sa.sql.column('default_nonmember_action', Enum(Action)),
     )
@@ -35,7 +35,7 @@ mailinglist_table = sa.sql.table(
 member_table = sa.sql.table(
     'member',
     sa.sql.column('id', sa.Integer),
-    sa.sql.column('list_id', sa.Unicode),
+    sa.sql.column('list_id', SAUnicode),
     sa.sql.column('role', Enum(MemberRole)),
     sa.sql.column('moderation_action', Enum(Action)),
     )
diff --git a/src/mailman/database/alembic/versions/d4fbb4fd34ca_header_match_order.py b/src/mailman/database/alembic/versions/d4fbb4fd34ca_header_match_order.py
index 2608bb812..313963b86 100644
--- a/src/mailman/database/alembic/versions/d4fbb4fd34ca_header_match_order.py
+++ b/src/mailman/database/alembic/versions/d4fbb4fd34ca_header_match_order.py
@@ -9,6 +9,7 @@ Create Date: 2016-02-01 15:57:09.807678
 import sqlalchemy as sa
 
 from alembic import op
+from mailman.database.helpers import is_mysql
 
 
 # Revision identifiers, used by Alembic.
@@ -20,19 +21,34 @@ def upgrade():
     with op.batch_alter_table('headermatch') as batch_op:
         batch_op.add_column(
             sa.Column('position', sa.Integer(), nullable=True))
-        batch_op.alter_column(
-            'mailing_list_id', existing_type=sa.INTEGER(), nullable=False)
         batch_op.create_index(
             op.f('ix_headermatch_position'), ['position'], unique=False)
-        batch_op.create_index(
-            op.f('ix_headermatch_mailing_list_id'), ['mailing_list_id'],
-            unique=False)
+        if not is_mysql(op.get_bind()):
+            # MySQL automatically creates indexes for primary keys.
+            batch_op.create_index(
+                op.f('ix_headermatch_mailing_list_id'), ['mailing_list_id'],
+                unique=False)
+            # MySQL doesn't allow changing columns used in a foreign key
+            # constrains since MySQL version 5.6.  We need to drop the
+            # constraint before changing the column.  But, since the
+            # constraint name is auto-generated, we can't really hardcode the
+            # name here to use batch_op.drop_constraint().  Until we have a
+            # better fix for this, it should be safe to skip this.
+            batch_op.alter_column(
+                'mailing_list_id', existing_type=sa.INTEGER(), nullable=False)
 
 
 def downgrade():
     with op.batch_alter_table('headermatch') as batch_op:
-        batch_op.drop_index(op.f('ix_headermatch_mailing_list_id'))
         batch_op.drop_index(op.f('ix_headermatch_position'))
-        batch_op.alter_column(
-            'mailing_list_id', existing_type=sa.INTEGER(), nullable=True)
         batch_op.drop_column('position')
+
+        if not is_mysql(op.get_bind()):
+            # MySQL automatically creates and removes the indexes for primary
+            # keys.  So, you cannot drop it without removing the foreign key
+            # constraint.
+            batch_op.drop_index(op.f('ix_headermatch_mailing_list_id'))
+            # MySQL doesn't allow changing columns used in foreign_key
+            # constraints.
+            batch_op.alter_column(
+                'mailing_list_id', existing_type=sa.INTEGER(), nullable=True)
diff --git a/src/mailman/database/alembic/versions/fa0d96e28631_template_manager.py b/src/mailman/database/alembic/versions/fa0d96e28631_template_manager.py
index 5920dd4e4..58d688453 100644
--- a/src/mailman/database/alembic/versions/fa0d96e28631_template_manager.py
+++ b/src/mailman/database/alembic/versions/fa0d96e28631_template_manager.py
@@ -12,6 +12,7 @@ import sqlalchemy as sa
 from alembic import op
 from mailman.config import config
 from mailman.database.helpers import exists_in_db
+from mailman.database.types import SAUnicode
 
 
 # revision identifiers, used by Alembic.
@@ -35,8 +36,8 @@ def upgrade():
     op.create_table(
         'file_cache',
         sa.Column('id', sa.Integer(), nullable=False),
-        sa.Column('key', sa.Unicode(), nullable=False),
-        sa.Column('file_id', sa.Unicode(), nullable=True),
+        sa.Column('key', SAUnicode(), nullable=False),
+        sa.Column('file_id', SAUnicode(), nullable=True),
         sa.Column('is_bytes', sa.Boolean(), nullable=False),
         sa.Column('created_on', sa.DateTime(), nullable=False),
         sa.Column('expires_on', sa.DateTime(), nullable=False),
@@ -45,10 +46,10 @@ def upgrade():
     template_table = op.create_table(
         'template',
         sa.Column('id', sa.Integer(), nullable=False),
-        sa.Column('name', sa.Unicode(), nullable=False),
-        sa.Column('context', sa.Unicode(), nullable=True),
-        sa.Column('uri', sa.Unicode(), nullable=False),
-        sa.Column('username', sa.Unicode(), nullable=True),
+        sa.Column('name', SAUnicode(), nullable=False),
+        sa.Column('context', SAUnicode(), nullable=True),
+        sa.Column('uri', SAUnicode(), nullable=False),
+        sa.Column('username', SAUnicode(), nullable=True),
         sa.Column('password', sa.DateTime(), nullable=True),
         sa.PrimaryKeyConstraint('id')
         )
@@ -60,13 +61,13 @@ def upgrade():
     mlist_table = sa.sql.table(
         'mailinglist',
         sa.sql.column('id', sa.Integer),
-        sa.sql.column('list_id', sa.Unicode),
-        sa.sql.column('digest_footer_uri', sa.Unicode),
-        sa.sql.column('digest_header_uri', sa.Unicode),
-        sa.sql.column('footer_uri', sa.Unicode),
-        sa.sql.column('header_uri', sa.Unicode),
-        sa.sql.column('goodbye_message_uri', sa.Unicode),
-        sa.sql.column('welcome_message_uri', sa.Unicode),
+        sa.sql.column('list_id', SAUnicode),
+        sa.sql.column('digest_footer_uri', SAUnicode),
+        sa.sql.column('digest_header_uri', SAUnicode),
+        sa.sql.column('footer_uri', SAUnicode),
+        sa.sql.column('header_uri', SAUnicode),
+        sa.sql.column('goodbye_message_uri', SAUnicode),
+        sa.sql.column('welcome_message_uri', SAUnicode),
         )
     for (mlist_id, list_id,
          digest_footer_uri, digest_header_uri,
@@ -131,30 +132,30 @@ def downgrade():
         if not exists_in_db(op.get_bind(), 'mailinglist', column):
             op.add_column(
                 'mailinglist',
-                sa.Column(column, sa.Unicode, nullable=True))
-    op.add_column('domain', sa.Column('base_url', sa.Unicode))
+                sa.Column(column, SAUnicode, nullable=True))
+    op.add_column('domain', sa.Column('base_url', SAUnicode))
     # Put all the templates with a context mapping the list-id back into the
     # mailinglist table.  No other contexts are supported, so just throw those
     # away.
     template_table = sa.sql.table(
         'template',
         sa.sql.column('id', sa.Integer),
-        sa.sql.column('name', sa.Unicode),
-        sa.sql.column('context', sa.Unicode),
-        sa.sql.column('uri', sa.Unicode),
-        sa.sql.column('username', sa.Unicode),
-        sa.sql.column('password', sa.Unicode),
+        sa.sql.column('name', SAUnicode),
+        sa.sql.column('context', SAUnicode),
+        sa.sql.column('uri', SAUnicode),
+        sa.sql.column('username', SAUnicode),
+        sa.sql.column('password', SAUnicode),
         )
     mlist_table = sa.sql.table(
         'mailinglist',
         sa.sql.column('id', sa.Integer),
-        sa.sql.column('list_id', sa.Unicode),
-        sa.sql.column('digest_footer_uri', sa.Unicode),
-        sa.sql.column('digest_header_uri', sa.Unicode),
-        sa.sql.column('footer_uri', sa.Unicode),
-        sa.sql.column('header_uri', sa.Unicode),
-        sa.sql.column('goodbye_message_uri', sa.Unicode),
-        sa.sql.column('welcome_message_uri', sa.Unicode),
+        sa.sql.column('list_id', SAUnicode),
+        sa.sql.column('digest_footer_uri', SAUnicode),
+        sa.sql.column('digest_header_uri', SAUnicode),
+        sa.sql.column('footer_uri', SAUnicode),
+        sa.sql.column('header_uri', SAUnicode),
+        sa.sql.column('goodbye_message_uri', SAUnicode),
+        sa.sql.column('welcome_message_uri', SAUnicode),
         )
     connection = op.get_bind()
     for (table_id, name, context, uri, username, password
diff --git a/src/mailman/database/base.py b/src/mailman/database/base.py
index dda3665af..f57228029 100644
--- a/src/mailman/database/base.py
+++ b/src/mailman/database/base.py
@@ -103,7 +103,7 @@ class SABaseDatabase:
         # engines, and yes, we could have chmod'd the file after the fact, but
         # half dozen and all...
         self.url = url
-        self.engine = create_engine(url)
+        self.engine = create_engine(url, isolation_level='READ UNCOMMITTED')
         session = sessionmaker(bind=self.engine)
         self.store = session()
         self.store.commit()
diff --git a/src/mailman/database/helpers.py b/src/mailman/database/helpers.py
index f58d559c5..b1dc381df 100644
--- a/src/mailman/database/helpers.py
+++ b/src/mailman/database/helpers.py
@@ -28,6 +28,11 @@ def is_sqlite(bind):
 
 
 @public
+def is_mysql(bind):
+    return bind.dialect.name == 'mysql'
+
+
+@public
 def exists_in_db(bind, tablename, columnname=None):
     md = sa.MetaData()
     md.reflect(bind=bind)
diff --git a/src/mailman/database/mysql.py b/src/mailman/database/mysql.py
new file mode 100644
index 000000000..0c0de54a9
--- /dev/null
+++ b/src/mailman/database/mysql.py
@@ -0,0 +1,34 @@
+# Copyright (C) 2016 by the Free Software Foundation, Inc.
+#
+# This file is part of GNU Mailman.
+#
+# GNU Mailman is free software: you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free
+# Software Foundation, either version 3 of the License, or (at your option)
+# any later version.
+#
+# GNU Mailman is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+# more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
+
+"""MySQL database support"""
+
+from mailman import public
+from mailman.database.base import SABaseDatabase
+from mailman.database.model import Model
+
+
+@public
+class MySQLDatabase(SABaseDatabase):
+    """Database class for MySQL."""
+
+    def _post_reset(self, store):
+        """Reset AUTO_INCREMENT counters for all the tables."""
+        super()._post_reset(store)
+        tables = reversed(Model.metadata.sorted_tables)
+        for table in tables:
+            store.execute('ALTER TABLE {} AUTO_INCREMENT = 1;'.format(table))
diff --git a/src/mailman/database/tests/test_factory.py b/src/mailman/database/tests/test_factory.py
index 74b45e43a..b0aa89fc4 100644
--- a/src/mailman/database/tests/test_factory.py
+++ b/src/mailman/database/tests/test_factory.py
@@ -24,10 +24,12 @@ from contextlib import suppress
 from mailman.config import config
 from mailman.database.alembic import alembic_cfg
 from mailman.database.factory import LAST_STORM_SCHEMA_VERSION, SchemaManager
+from mailman.database.helpers import is_mysql
 from mailman.database.model import Model
+from mailman.database.types import SAUnicode
 from mailman.interfaces.database import DatabaseError
 from mailman.testing.layers import ConfigLayer
-from sqlalchemy import Column, Integer, MetaData, Table, Unicode
+from sqlalchemy import Column, Integer, MetaData, Table
 from sqlalchemy.exc import OperationalError, ProgrammingError
 from sqlalchemy.schema import Index
 from unittest.mock import patch
@@ -60,8 +62,8 @@ class TestSchemaManager(unittest.TestCase):
         version_table = Table(
             'version', Model.metadata,
             Column('id', Integer, primary_key=True),
-            Column('component', Unicode),
-            Column('version', Unicode),
+            Column('component', SAUnicode),
+            Column('version', SAUnicode),
             )
         version_table.create(config.db.engine)
         config.db.store.execute(version_table.insert().values(
@@ -71,12 +73,15 @@ class TestSchemaManager(unittest.TestCase):
         # all DB engines...
         config.db.engine.execute(
             'ALTER TABLE mailinglist ADD COLUMN acceptable_aliases_id INT')
-        Index('ix_user__user_id').drop(bind=config.db.engine)
-        # Don't pollute our main metadata object, create a new one.
-        md = MetaData()
-        user_table = Model.metadata.tables['user'].tometadata(md)
-        Index('ix_user_user_id', user_table.c._user_id).create(
-            bind=config.db.engine)
+        # In case of MySQL, you cannot create/drop indexes on primary keys
+        # manually as it is handled automatically by MySQL.
+        if not is_mysql(config.db.engine):
+            Index('ix_user__user_id').drop(bind=config.db.engine)
+            # Don't pollute our main metadata object, create a new one.
+            md = MetaData()
+            user_table = Model.metadata.tables['user'].tometadata(md)
+            Index('ix_user_user_id', user_table.c._user_id).create(
+                bind=config.db.engine)
         config.db.commit()
 
     def _drop_storm_database(self):
@@ -88,10 +93,12 @@ class TestSchemaManager(unittest.TestCase):
             version = Model.metadata.tables['version']
             version.drop(config.db.engine, checkfirst=True)
             Model.metadata.remove(version)
-        # If it's nonexistent, PostgreSQL raises a ProgrammingError, while
-        # SQLite raises an OperationalError.
-        with suppress(ProgrammingError, OperationalError):
-            Index('ix_user_user_id').drop(bind=config.db.engine)
+        # If it's nonexistent, PostgreSQL raises a ProgrammingError while
+        # SQLite raises an OperationalError. Since MySQL automatically handles
+        # indexes for primary keys, don't try doing it with that backend.
+        if not is_mysql(config.db.engine):
+            with suppress(ProgrammingError, OperationalError):
+                Index('ix_user_user_id').drop(bind=config.db.engine)
         config.db.commit()
 
     def test_current_database(self):
diff --git a/src/mailman/database/tests/test_migrations.py b/src/mailman/database/tests/test_migrations.py
index 88a2a30ab..2ad41ae53 100644
--- a/src/mailman/database/tests/test_migrations.py
+++ b/src/mailman/database/tests/test_migrations.py
@@ -28,7 +28,7 @@ from mailman.database.alembic import alembic_cfg
 from mailman.database.helpers import exists_in_db
 from mailman.database.model import Model
 from mailman.database.transaction import transaction
-from mailman.database.types import Enum
+from mailman.database.types import Enum, SAUnicode
 from mailman.interfaces.action import Action
 from mailman.interfaces.cache import ICacheManager
 from mailman.interfaces.member import MemberRole
@@ -83,8 +83,8 @@ class TestMigrations(unittest.TestCase):
         header_match_table = sa.sql.table(
             'headermatch',
             sa.sql.column('mailing_list_id', sa.Integer),
-            sa.sql.column('header', sa.Unicode),
-            sa.sql.column('pattern', sa.Unicode),
+            sa.sql.column('header', SAUnicode),
+            sa.sql.column('pattern', SAUnicode),
             )
         # Bring the DB to the revision that is being tested.
         alembic.command.downgrade(alembic_cfg, '42756496720')
@@ -126,8 +126,8 @@ class TestMigrations(unittest.TestCase):
         keyvalue_table = sa.sql.table(
             'pendedkeyvalue',
             sa.sql.column('id', sa.Integer),
-            sa.sql.column('key', sa.Unicode),
-            sa.sql.column('value', sa.Unicode),
+            sa.sql.column('key', SAUnicode),
+            sa.sql.column('value', SAUnicode),
             sa.sql.column('pended_id', sa.Integer),
             )
         def get_from_db():                                 # noqa: E301
@@ -230,14 +230,14 @@ class TestMigrations(unittest.TestCase):
         sa.sql.table(
             'mailinglist',
             sa.sql.column('id', sa.Integer),
-            sa.sql.column('list_id', sa.Unicode),
+            sa.sql.column('list_id', SAUnicode),
             sa.sql.column('default_member_action', Enum(Action)),
             sa.sql.column('default_nonmember_action', Enum(Action)),
             )
         member_table = sa.sql.table(
             'member',
             sa.sql.column('id', sa.Integer),
-            sa.sql.column('list_id', sa.Unicode),
+            sa.sql.column('list_id', SAUnicode),
             sa.sql.column('address_id', sa.Integer),
             sa.sql.column('role', Enum(MemberRole)),
             sa.sql.column('moderation_action', Enum(Action)),
diff --git a/src/mailman/database/types.py b/src/mailman/database/types.py
index 28b261514..bbd040d96 100644
--- a/src/mailman/database/types.py
+++ b/src/mailman/database/types.py
@@ -22,7 +22,8 @@ import uuid
 from mailman import public
 from sqlalchemy import Integer
 from sqlalchemy.dialects import postgresql
-from sqlalchemy.types import CHAR, TypeDecorator
+from sqlalchemy.ext.compiler import compiles
+from sqlalchemy.types import CHAR, TypeDecorator, Unicode
 
 
 @public
@@ -80,3 +81,46 @@ class UUID(TypeDecorator):
             return value
         else:
             return uuid.UUID(value)
+
+
+@public
+class SAUnicode(TypeDecorator):
+    """Unicode datatype to support fixed length VARCHAR in MySQL.
+
+    This type compiles to VARCHAR(255) in case of MySQL, and in case of
+    other dailects defaults to the Unicode type.  This was created so
+    that we don't have to alter the output of the default Unicode data
+    type and it can still be used if needed in the codebase.
+    """
+    impl = Unicode
+
+
+@compiles(SAUnicode)
+def default_sa_unicode(element, compiler, **kw):
+    return compiler.visit_Unicode(element, **kw)
+
+
+@compiles(SAUnicode, 'mysql')
+def compile_sa_unicode(element, compiler, **kw):
+    # We hardcode the collate here to make string comparison case sensitive.
+    return 'VARCHAR(255) COLLATE utf8_bin'
+
+
+@public
+class SAUnicodeLarge(TypeDecorator):
+    """Similar to SAUnicode type, but compiles to VARCHAR(510).
+
+    This is double size of SAUnicode defined above.
+    """
+    impl = Unicode
+
+
+@compiles(SAUnicodeLarge, 'mysql')
+def compile_sa_unicode_large(element, compiler, **kw):
+    # We hardcode the collate here to make string comparison case sensitive.
+    return 'VARCHAR(510) COLLATE utf8_bin'
+
+
+@compiles(SAUnicode)
+def defalt_sa_unicode_large(element, compiler, **kw):
+    return compiler.visit_unicode(element, **kw)