diff --git a/data_diff/databases/base.py b/data_diff/databases/base.py
index 9dc03909..871c650d 100644
--- a/data_diff/databases/base.py
+++ b/data_diff/databases/base.py
@@ -199,10 +199,19 @@ def apply_query(callback: Callable[[str], Any], sql_code: Union[str, ThreadLocal
 class BaseDialect(abc.ABC):
     SUPPORTS_PRIMARY_KEY: ClassVar[bool] = False
     SUPPORTS_INDEXES: ClassVar[bool] = False
+    PREVENT_OVERFLOW_WHEN_CONCAT: ClassVar[bool] = False
     TYPE_CLASSES: ClassVar[Dict[str, Type[ColType]]] = {}
 
     PLACEHOLDER_TABLE = None  # Used for Oracle
 
+    # Some database do not support long string so concatenation might lead to type overflow
+
+    _prevent_overflow_when_concat: bool = False
+
+    def enable_preventing_type_overflow(self) -> None:
+        logger.info("Preventing type overflow when concatenation is enabled")
+        self._prevent_overflow_when_concat = True
+
     def parse_table_name(self, name: str) -> DbPath:
         "Parse the given table name into a DbPath"
         return parse_table_name(name)
@@ -392,10 +401,19 @@ def render_checksum(self, c: Compiler, elem: Checksum) -> str:
         return f"sum({md5})"
 
     def render_concat(self, c: Compiler, elem: Concat) -> str:
+        if self._prevent_overflow_when_concat:
+            items = [
+                f"{self.compile(c, Code(self.md5_as_hex(self.to_string(self.compile(c, expr)))))}"
+                for expr in elem.exprs
+            ]
+
         # We coalesce because on some DBs (e.g. MySQL) concat('a', NULL) is NULL
-        items = [
-            f"coalesce({self.compile(c, Code(self.to_string(self.compile(c, expr))))}, '<null>')" for expr in elem.exprs
-        ]
+        else:
+            items = [
+                f"coalesce({self.compile(c, Code(self.to_string(self.compile(c, expr))))}, '<null>')"
+                for expr in elem.exprs
+            ]
+
         assert items
         if len(items) == 1:
             return items[0]
@@ -769,6 +787,10 @@ def set_timezone_to_utc(self) -> str:
     def md5_as_int(self, s: str) -> str:
         "Provide SQL for computing md5 and returning an int"
 
+    @abstractmethod
+    def md5_as_hex(self, s: str) -> str:
+        """Method to calculate MD5"""
+
     @abstractmethod
     def normalize_timestamp(self, value: str, coltype: TemporalType) -> str:
         """Creates an SQL expression, that converts 'value' to a normalized timestamp.
@@ -885,6 +907,8 @@ class Database(abc.ABC):
     Instanciated using :meth:`~data_diff.connect`
     """
 
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = BaseDialect
+
     SUPPORTS_ALPHANUMS: ClassVar[bool] = True
     SUPPORTS_UNIQUE_CONSTAINT: ClassVar[bool] = False
     CONNECT_URI_KWPARAMS: ClassVar[List[str]] = []
@@ -892,6 +916,7 @@ class Database(abc.ABC):
     default_schema: Optional[str] = None
     _interactive: bool = False
     is_closed: bool = False
+    _dialect: BaseDialect = None
 
     @property
     def name(self):
@@ -1120,10 +1145,13 @@ def close(self):
         return super().close()
 
     @property
-    @abstractmethod
     def dialect(self) -> BaseDialect:
         "The dialect of the database. Used internally by Database, and also available publicly."
 
+        if not self._dialect:
+            self._dialect = self.DIALECT_CLASS()
+        return self._dialect
+
     @property
     @abstractmethod
     def CONNECT_URI_HELP(self) -> str:
diff --git a/data_diff/databases/bigquery.py b/data_diff/databases/bigquery.py
index e672b928..26d8aec3 100644
--- a/data_diff/databases/bigquery.py
+++ b/data_diff/databases/bigquery.py
@@ -1,5 +1,5 @@
 import re
-from typing import Any, List, Union
+from typing import Any, ClassVar, List, Union, Type
 
 import attrs
 
@@ -134,6 +134,9 @@ def parse_table_name(self, name: str) -> DbPath:
     def md5_as_int(self, s: str) -> str:
         return f"cast(cast( ('0x' || substr(TO_HEX(md5({s})), {1+MD5_HEXDIGITS-CHECKSUM_HEXDIGITS})) as int64) as numeric) - {CHECKSUM_OFFSET}"
 
+    def md5_as_hex(self, s: str) -> str:
+        return f"md5({s})"
+
     def normalize_timestamp(self, value: str, coltype: TemporalType) -> str:
         if coltype.rounds:
             timestamp = f"timestamp_micros(cast(round(unix_micros(cast({value} as timestamp))/1000000, {coltype.precision})*1000000 as int))"
@@ -179,9 +182,9 @@ def normalize_struct(self, value: str, _coltype: Struct) -> str:
 
 @attrs.define(frozen=False, init=False, kw_only=True)
 class BigQuery(Database):
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = Dialect
     CONNECT_URI_HELP = "bigquery://<project>/<dataset>"
     CONNECT_URI_PARAMS = ["dataset"]
-    dialect = Dialect()
 
     project: str
     dataset: str
diff --git a/data_diff/databases/clickhouse.py b/data_diff/databases/clickhouse.py
index 7a8816d8..13082504 100644
--- a/data_diff/databases/clickhouse.py
+++ b/data_diff/databases/clickhouse.py
@@ -1,4 +1,4 @@
-from typing import Any, Dict, Optional, Type
+from typing import Any, ClassVar, Dict, Optional, Type
 
 import attrs
 
@@ -105,6 +105,9 @@ def md5_as_int(self, s: str) -> str:
             f"reinterpretAsUInt128(reverse(unhex(lowerUTF8(substr(hex(MD5({s})), {substr_idx}))))) - {CHECKSUM_OFFSET}"
         )
 
+    def md5_as_hex(self, s: str) -> str:
+        return f"hex(MD5({s}))"
+
     def normalize_number(self, value: str, coltype: FractionalType) -> str:
         # If a decimal value has trailing zeros in a fractional part, when casting to string they are dropped.
         # For example:
@@ -164,7 +167,7 @@ def normalize_timestamp(self, value: str, coltype: TemporalType) -> str:
 
 @attrs.define(frozen=False, init=False, kw_only=True)
 class Clickhouse(ThreadedDatabase):
-    dialect = Dialect()
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = Dialect
     CONNECT_URI_HELP = "clickhouse://<user>:<password>@<host>/<database>"
     CONNECT_URI_PARAMS = ["database?"]
 
diff --git a/data_diff/databases/databricks.py b/data_diff/databases/databricks.py
index 7394f2df..19a1f103 100644
--- a/data_diff/databases/databricks.py
+++ b/data_diff/databases/databricks.py
@@ -1,5 +1,5 @@
 import math
-from typing import Any, Dict, Sequence
+from typing import Any, ClassVar, Dict, Sequence, Type
 import logging
 
 import attrs
@@ -82,6 +82,9 @@ def parse_table_name(self, name: str) -> DbPath:
     def md5_as_int(self, s: str) -> str:
         return f"cast(conv(substr(md5({s}), {1+MD5_HEXDIGITS-CHECKSUM_HEXDIGITS}), 16, 10) as decimal(38, 0)) - {CHECKSUM_OFFSET}"
 
+    def md5_as_hex(self, s: str) -> str:
+        return f"md5({s})"
+
     def normalize_timestamp(self, value: str, coltype: TemporalType) -> str:
         """Databricks timestamp contains no more than 6 digits in precision"""
 
@@ -104,7 +107,7 @@ def normalize_boolean(self, value: str, _coltype: Boolean) -> str:
 
 @attrs.define(frozen=False, init=False, kw_only=True)
 class Databricks(ThreadedDatabase):
-    dialect = Dialect()
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = Dialect
     CONNECT_URI_HELP = "databricks://:<access_token>@<server_hostname>/<http_path>"
     CONNECT_URI_PARAMS = ["catalog", "schema"]
 
diff --git a/data_diff/databases/duckdb.py b/data_diff/databases/duckdb.py
index a105b71a..6c65b16b 100644
--- a/data_diff/databases/duckdb.py
+++ b/data_diff/databases/duckdb.py
@@ -1,4 +1,4 @@
-from typing import Any, Dict, Union
+from typing import Any, ClassVar, Dict, Union, Type
 
 import attrs
 
@@ -100,6 +100,9 @@ def current_timestamp(self) -> str:
     def md5_as_int(self, s: str) -> str:
         return f"('0x' || SUBSTRING(md5({s}), {1+MD5_HEXDIGITS-CHECKSUM_HEXDIGITS},{CHECKSUM_HEXDIGITS}))::BIGINT - {CHECKSUM_OFFSET}"
 
+    def md5_as_hex(self, s: str) -> str:
+        return f"md5({s})"
+
     def normalize_timestamp(self, value: str, coltype: TemporalType) -> str:
         # It's precision 6 by default. If precision is less than 6 -> we remove the trailing numbers.
         if coltype.rounds and coltype.precision > 0:
@@ -116,7 +119,7 @@ def normalize_boolean(self, value: str, _coltype: Boolean) -> str:
 
 @attrs.define(frozen=False, init=False, kw_only=True)
 class DuckDB(Database):
-    dialect = Dialect()
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = Dialect
     SUPPORTS_UNIQUE_CONSTAINT = False  # Temporary, until we implement it
     CONNECT_URI_HELP = "duckdb://<dbname>@<filepath>"
     CONNECT_URI_PARAMS = ["database", "dbpath"]
diff --git a/data_diff/databases/mssql.py b/data_diff/databases/mssql.py
index fd23bef1..8f5195ee 100644
--- a/data_diff/databases/mssql.py
+++ b/data_diff/databases/mssql.py
@@ -1,4 +1,4 @@
-from typing import Any, Dict, Optional
+from typing import Any, ClassVar, Dict, Optional, Type
 
 import attrs
 
@@ -38,7 +38,7 @@ def import_mssql():
 class Dialect(BaseDialect):
     name = "MsSQL"
     ROUNDS_ON_PREC_LOSS = True
-    SUPPORTS_PRIMARY_KEY = True
+    SUPPORTS_PRIMARY_KEY: ClassVar[bool] = True
     SUPPORTS_INDEXES = True
     TYPE_CLASSES = {
         # Timestamps
@@ -151,10 +151,13 @@ def normalize_number(self, value: str, coltype: NumericType) -> str:
     def md5_as_int(self, s: str) -> str:
         return f"convert(bigint, convert(varbinary, '0x' + RIGHT(CONVERT(NVARCHAR(32), HashBytes('MD5', {s}), 2), {CHECKSUM_HEXDIGITS}), 1)) - {CHECKSUM_OFFSET}"
 
+    def md5_as_hex(self, s: str) -> str:
+        return f"HashBytes('MD5', {s})"
+
 
 @attrs.define(frozen=False, init=False, kw_only=True)
 class MsSQL(ThreadedDatabase):
-    dialect = Dialect()
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = Dialect
     CONNECT_URI_HELP = "mssql://<user>:<password>@<host>/<database>/<schema>"
     CONNECT_URI_PARAMS = ["database", "schema"]
 
diff --git a/data_diff/databases/mysql.py b/data_diff/databases/mysql.py
index f4993b87..647388f2 100644
--- a/data_diff/databases/mysql.py
+++ b/data_diff/databases/mysql.py
@@ -1,4 +1,4 @@
-from typing import Any, Dict
+from typing import Any, ClassVar, Dict, Type
 
 import attrs
 
@@ -40,7 +40,7 @@ def import_mysql():
 class Dialect(BaseDialect):
     name = "MySQL"
     ROUNDS_ON_PREC_LOSS = True
-    SUPPORTS_PRIMARY_KEY = True
+    SUPPORTS_PRIMARY_KEY: ClassVar[bool] = True
     SUPPORTS_INDEXES = True
     TYPE_CLASSES = {
         # Dates
@@ -101,6 +101,9 @@ def set_timezone_to_utc(self) -> str:
     def md5_as_int(self, s: str) -> str:
         return f"conv(substring(md5({s}), {1+MD5_HEXDIGITS-CHECKSUM_HEXDIGITS}), 16, 10) - {CHECKSUM_OFFSET}"
 
+    def md5_as_hex(self, s: str) -> str:
+        return f"md5({s})"
+
     def normalize_timestamp(self, value: str, coltype: TemporalType) -> str:
         if coltype.rounds:
             return self.to_string(f"cast( cast({value} as datetime({coltype.precision})) as datetime(6))")
@@ -117,7 +120,7 @@ def normalize_uuid(self, value: str, coltype: ColType_UUID) -> str:
 
 @attrs.define(frozen=False, init=False, kw_only=True)
 class MySQL(ThreadedDatabase):
-    dialect = Dialect()
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = Dialect
     SUPPORTS_ALPHANUMS = False
     SUPPORTS_UNIQUE_CONSTAINT = True
     CONNECT_URI_HELP = "mysql://<user>:<password>@<host>/<database>"
diff --git a/data_diff/databases/oracle.py b/data_diff/databases/oracle.py
index 32bd30ef..ab84f0b6 100644
--- a/data_diff/databases/oracle.py
+++ b/data_diff/databases/oracle.py
@@ -1,4 +1,4 @@
-from typing import Any, Dict, List, Optional
+from typing import Any, ClassVar, Dict, List, Optional, Type
 
 import attrs
 
@@ -43,7 +43,7 @@ class Dialect(
     BaseDialect,
 ):
     name = "Oracle"
-    SUPPORTS_PRIMARY_KEY = True
+    SUPPORTS_PRIMARY_KEY: ClassVar[bool] = True
     SUPPORTS_INDEXES = True
     TYPE_CLASSES: Dict[str, type] = {
         "NUMBER": Decimal,
@@ -137,6 +137,9 @@ def md5_as_int(self, s: str) -> str:
         # TODO: Find a way to use UTL_RAW.CAST_TO_BINARY_INTEGER ?
         return f"to_number(substr(standard_hash({s}, 'MD5'), {1+MD5_HEXDIGITS-CHECKSUM_HEXDIGITS}), 'xxxxxxxxxxxxxxx') - {CHECKSUM_OFFSET}"
 
+    def md5_as_hex(self, s: str) -> str:
+        return f"standard_hash({s}, 'MD5')"
+
     def normalize_uuid(self, value: str, coltype: ColType_UUID) -> str:
         # Cast is necessary for correct MD5 (trimming not enough)
         return f"CAST(TRIM({value}) AS VARCHAR(36))"
@@ -161,7 +164,7 @@ def normalize_number(self, value: str, coltype: FractionalType) -> str:
 
 @attrs.define(frozen=False, init=False, kw_only=True)
 class Oracle(ThreadedDatabase):
-    dialect = Dialect()
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = Dialect
     CONNECT_URI_HELP = "oracle://<user>:<password>@<host>/<database>"
     CONNECT_URI_PARAMS = ["database?"]
 
diff --git a/data_diff/databases/postgresql.py b/data_diff/databases/postgresql.py
index 075d6aff..4b9e945f 100644
--- a/data_diff/databases/postgresql.py
+++ b/data_diff/databases/postgresql.py
@@ -42,7 +42,7 @@ def import_postgresql():
 class PostgresqlDialect(BaseDialect):
     name = "PostgreSQL"
     ROUNDS_ON_PREC_LOSS = True
-    SUPPORTS_PRIMARY_KEY = True
+    SUPPORTS_PRIMARY_KEY: ClassVar[bool] = True
     SUPPORTS_INDEXES = True
 
     TYPE_CLASSES: ClassVar[Dict[str, Type[ColType]]] = {
@@ -98,6 +98,9 @@ def type_repr(self, t) -> str:
     def md5_as_int(self, s: str) -> str:
         return f"('x' || substring(md5({s}), {1+MD5_HEXDIGITS-CHECKSUM_HEXDIGITS}))::bit({_CHECKSUM_BITSIZE})::bigint - {CHECKSUM_OFFSET}"
 
+    def md5_as_hex(self, s: str) -> str:
+        return f"md5({s})"
+
     def normalize_timestamp(self, value: str, coltype: TemporalType) -> str:
         if coltype.rounds:
             return f"to_char({value}::timestamp({coltype.precision}), 'YYYY-mm-dd HH24:MI:SS.US')"
@@ -119,7 +122,7 @@ def normalize_json(self, value: str, _coltype: JSON) -> str:
 
 @attrs.define(frozen=False, init=False, kw_only=True)
 class PostgreSQL(ThreadedDatabase):
-    dialect = PostgresqlDialect()
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = PostgresqlDialect
     SUPPORTS_UNIQUE_CONSTAINT = True
     CONNECT_URI_HELP = "postgresql://<user>:<password>@<host>/<database>"
     CONNECT_URI_PARAMS = ["database?"]
diff --git a/data_diff/databases/presto.py b/data_diff/databases/presto.py
index f575719a..ba1c7360 100644
--- a/data_diff/databases/presto.py
+++ b/data_diff/databases/presto.py
@@ -1,6 +1,6 @@
 from functools import partial
 import re
-from typing import Any
+from typing import Any, ClassVar, Type
 
 import attrs
 
@@ -128,6 +128,9 @@ def current_timestamp(self) -> str:
     def md5_as_int(self, s: str) -> str:
         return f"cast(from_base(substr(to_hex(md5(to_utf8({s}))), {1+MD5_HEXDIGITS-CHECKSUM_HEXDIGITS}), 16) as decimal(38, 0)) - {CHECKSUM_OFFSET}"
 
+    def md5_as_hex(self, s: str) -> str:
+        return f"to_hex(md5(to_utf8({s})))"
+
     def normalize_uuid(self, value: str, coltype: ColType_UUID) -> str:
         # Trim doesn't work on CHAR type
         return f"TRIM(CAST({value} AS VARCHAR))"
@@ -150,7 +153,7 @@ def normalize_boolean(self, value: str, _coltype: Boolean) -> str:
 
 @attrs.define(frozen=False, init=False, kw_only=True)
 class Presto(Database):
-    dialect = Dialect()
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = Dialect
     CONNECT_URI_HELP = "presto://<user>@<host>/<catalog>/<schema>"
     CONNECT_URI_PARAMS = ["catalog", "schema"]
 
diff --git a/data_diff/databases/redshift.py b/data_diff/databases/redshift.py
index 968f57bb..7a621f57 100644
--- a/data_diff/databases/redshift.py
+++ b/data_diff/databases/redshift.py
@@ -12,6 +12,7 @@
     TimestampTZ,
 )
 from data_diff.databases.postgresql import (
+    BaseDialect,
     PostgreSQL,
     MD5_HEXDIGITS,
     CHECKSUM_HEXDIGITS,
@@ -47,6 +48,9 @@ def type_repr(self, t) -> str:
     def md5_as_int(self, s: str) -> str:
         return f"strtol(substring(md5({s}), {1+MD5_HEXDIGITS-CHECKSUM_HEXDIGITS}), 16)::decimal(38) - {CHECKSUM_OFFSET}"
 
+    def md5_as_hex(self, s: str) -> str:
+        return f"md5({s})"
+
     def normalize_timestamp(self, value: str, coltype: TemporalType) -> str:
         if coltype.rounds:
             timestamp = f"{value}::timestamp(6)"
@@ -76,7 +80,7 @@ def normalize_json(self, value: str, _coltype: JSON) -> str:
 
 @attrs.define(frozen=False, init=False, kw_only=True)
 class Redshift(PostgreSQL):
-    dialect = Dialect()
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = Dialect
     CONNECT_URI_HELP = "redshift://<user>:<password>@<host>/<database>"
     CONNECT_URI_PARAMS = ["database?"]
 
diff --git a/data_diff/databases/snowflake.py b/data_diff/databases/snowflake.py
index 857e7c89..bedacd80 100644
--- a/data_diff/databases/snowflake.py
+++ b/data_diff/databases/snowflake.py
@@ -1,4 +1,4 @@
-from typing import Any, Union, List
+from typing import Any, ClassVar, Union, List, Type
 import logging
 
 import attrs
@@ -76,6 +76,9 @@ def type_repr(self, t) -> str:
     def md5_as_int(self, s: str) -> str:
         return f"BITAND(md5_number_lower64({s}), {CHECKSUM_MASK}) - {CHECKSUM_OFFSET}"
 
+    def md5_as_hex(self, s: str) -> str:
+        return f"md5({s})"
+
     def normalize_timestamp(self, value: str, coltype: TemporalType) -> str:
         if coltype.rounds:
             timestamp = f"to_timestamp(round(date_part(epoch_nanosecond, convert_timezone('UTC', {value})::timestamp(9))/1000000000, {coltype.precision}))"
@@ -93,7 +96,7 @@ def normalize_boolean(self, value: str, _coltype: Boolean) -> str:
 
 @attrs.define(frozen=False, init=False, kw_only=True)
 class Snowflake(Database):
-    dialect = Dialect()
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = Dialect
     CONNECT_URI_HELP = "snowflake://<user>:<password>@<account>/<database>/<SCHEMA>?warehouse=<WAREHOUSE>"
     CONNECT_URI_PARAMS = ["database", "schema"]
     CONNECT_URI_KWPARAMS = ["warehouse"]
diff --git a/data_diff/databases/trino.py b/data_diff/databases/trino.py
index f0c95ee4..b76ba74b 100644
--- a/data_diff/databases/trino.py
+++ b/data_diff/databases/trino.py
@@ -1,11 +1,11 @@
-from typing import Any
+from typing import Any, ClassVar, Type
 
 import attrs
 
 from data_diff.abcs.database_types import TemporalType, ColType_UUID
 from data_diff.databases import presto
 from data_diff.databases.base import import_helper
-from data_diff.databases.base import TIMESTAMP_PRECISION_POS
+from data_diff.databases.base import TIMESTAMP_PRECISION_POS, BaseDialect
 
 
 @import_helper("trino")
@@ -34,7 +34,7 @@ def normalize_uuid(self, value: str, coltype: ColType_UUID) -> str:
 
 @attrs.define(frozen=False, init=False, kw_only=True)
 class Trino(presto.Presto):
-    dialect = Dialect()
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = Dialect
     CONNECT_URI_HELP = "trino://<user>@<host>/<catalog>/<schema>"
     CONNECT_URI_PARAMS = ["catalog", "schema"]
 
diff --git a/data_diff/databases/vertica.py b/data_diff/databases/vertica.py
index 51dc00fa..23f63acc 100644
--- a/data_diff/databases/vertica.py
+++ b/data_diff/databases/vertica.py
@@ -1,4 +1,4 @@
-from typing import Any, Dict, List
+from typing import Any, ClassVar, Dict, List, Type
 
 import attrs
 
@@ -36,6 +36,7 @@ def import_vertica():
     return vertica_python
 
 
+@attrs.define(frozen=False)
 class Dialect(BaseDialect):
     name = "Vertica"
     ROUNDS_ON_PREC_LOSS = True
@@ -109,6 +110,9 @@ def current_timestamp(self) -> str:
     def md5_as_int(self, s: str) -> str:
         return f"CAST(HEX_TO_INTEGER(SUBSTRING(MD5({s}), {1 + MD5_HEXDIGITS - CHECKSUM_HEXDIGITS})) AS NUMERIC(38, 0)) - {CHECKSUM_OFFSET}"
 
+    def md5_as_hex(self, s: str) -> str:
+        return f"MD5({s})"
+
     def normalize_timestamp(self, value: str, coltype: TemporalType) -> str:
         if coltype.rounds:
             return f"TO_CHAR({value}::TIMESTAMP({coltype.precision}), 'YYYY-MM-DD HH24:MI:SS.US')"
@@ -131,7 +135,7 @@ def normalize_boolean(self, value: str, _coltype: Boolean) -> str:
 
 @attrs.define(frozen=False, init=False, kw_only=True)
 class Vertica(ThreadedDatabase):
-    dialect = Dialect()
+    DIALECT_CLASS: ClassVar[Type[BaseDialect]] = Dialect
     CONNECT_URI_HELP = "vertica://<user>:<password>@<host>/<database>"
     CONNECT_URI_PARAMS = ["database?"]
 
diff --git a/data_diff/diff_tables.py b/data_diff/diff_tables.py
index 44daba34..66802426 100644
--- a/data_diff/diff_tables.py
+++ b/data_diff/diff_tables.py
@@ -208,6 +208,10 @@ def _diff_tables_wrapper(self, table1: TableSegment, table2: TableSegment, info_
             event_json = create_start_event_json(options)
             run_as_daemon(send_event_json, event_json)
 
+        if table1.database.dialect.PREVENT_OVERFLOW_WHEN_CONCAT or table2.database.dialect.PREVENT_OVERFLOW_WHEN_CONCAT:
+            table1.database.dialect.enable_preventing_type_overflow()
+            table2.database.dialect.enable_preventing_type_overflow()
+
         start = time.monotonic()
         error = None
         try:
diff --git a/tests/test_joindiff.py b/tests/test_joindiff.py
index ed8a31b6..0f664c45 100644
--- a/tests/test_joindiff.py
+++ b/tests/test_joindiff.py
@@ -270,7 +270,9 @@ def test_null_pks(self):
         self.assertRaises(ValueError, list, x)
 
 
-@test_each_database_in_list(d for d in TEST_DATABASES if d.dialect.SUPPORTS_PRIMARY_KEY and d.SUPPORTS_UNIQUE_CONSTAINT)
+@test_each_database_in_list(
+    d for d in TEST_DATABASES if d.DIALECT_CLASS.SUPPORTS_PRIMARY_KEY and d.SUPPORTS_UNIQUE_CONSTAINT
+)
 class TestUniqueConstraint(DiffTestCase):
     def setUp(self):
         super().setUp()
diff --git a/tests/test_query.py b/tests/test_query.py
index 0625a75d..2585c02e 100644
--- a/tests/test_query.py
+++ b/tests/test_query.py
@@ -76,6 +76,9 @@ def optimizer_hints(self, s: str):
     def md5_as_int(self, s: str) -> str:
         raise NotImplementedError
 
+    def md5_as_hex(self, s: str) -> str:
+        raise NotImplementedError
+
     def normalize_number(self, value: str, coltype: FractionalType) -> str:
         raise NotImplementedError