fix hardcoded offsets in mssql and snowflake

Author: vvkh

data_diff/databases/mssql.py

@@ -7,6 +7,7 @@
     CHECKSUM_HEXDIGITS,
     Mixin_OptimizerHints,
     Mixin_RandomSample,
+    CHECKSUM_OFFSET,
     QueryError,
     ThreadedDatabase,
     import_helper,
@@ -60,8 +61,7 @@ def normalize_number(self, value: str, coltype: FractionalType) -> str:
 @attrs.define(frozen=False)
 class Mixin_MD5(AbstractMixin_MD5):
     def md5_as_int(self, s: str) -> str:
-        offset = 549755813887
-        return f"convert(bigint, convert(varbinary, '0x' + RIGHT(CONVERT(NVARCHAR(32), HashBytes('MD5', {s}), 2), {CHECKSUM_HEXDIGITS}), 1)) - {offset}"
+        return f"convert(bigint, convert(varbinary, '0x' + RIGHT(CONVERT(NVARCHAR(32), HashBytes('MD5', {s}), 2), {CHECKSUM_HEXDIGITS}), 1)) - {CHECKSUM_OFFSET}"
 
 
 @attrs.define(frozen=False)

data_diff/databases/snowflake.py

@@ -30,6 +30,7 @@
     import_helper,
     CHECKSUM_MASK,
     ThreadLocalInterpreter,
+    CHECKSUM_OFFSET,
     Mixin_RandomSample,
 )
 
@@ -46,8 +47,7 @@ def import_snowflake():
 @attrs.define(frozen=False)
 class Mixin_MD5(AbstractMixin_MD5):
     def md5_as_int(self, s: str) -> str:
-        offset = 549755813887
-        return f"BITAND(md5_number_lower64({s}), {CHECKSUM_MASK}) - {offset}"
+        return f"BITAND(md5_number_lower64({s}), {CHECKSUM_MASK}) - {CHECKSUM_OFFSET}"
 
 
 @attrs.define(frozen=False)