feat: add db2 hash and concat support (#800)

* feat: add db2 hash and concat support

* fix import error when db2 not installed

* fix: return lowercase hash

* chore: update README

* feat: add rand support for Db2

README.md

@@ -136,7 +136,7 @@ The [Examples](https://github.com/GoogleCloudPlatform/professional-services-data
 
 #### Row Validations
 
-(Note: Row hash validation is currently supported for BigQuery, Teradata, Impala/Hive, Oracle, SQL Server, Postgres, and Alloy DB. Struct and array data types are not currently supported.
+(Note: Row hash validation is currently supported for BigQuery, Teradata, Impala/Hive, Oracle, SQL Server, Postgres, Db2 and Alloy DB. Struct and array data types are not currently supported.
 In addition, please note that SHA256 is not a supported function on Teradata systems. 
 If you wish to perform this comparison on Teradata you will need to 
 [deploy a UDF to perform the conversion](https://github.com/akuroda/teradata-udf-sha2/blob/master/src/sha256.c).)

data_validation/query_builder/random_row_builder.py

@@ -52,6 +52,7 @@
     clients.OracleClient: "DBMS_RANDOM.VALUE",
     PostgreSQLClient: "RANDOM()",
     clients.MSSQLClient: "NEWID()",
+    clients.DB2Client: "RAND()",
 }
 
 

third_party/ibis/ibis_DB2/alchemy.py

@@ -29,6 +29,7 @@
     dt.BIGINT: sa.BIGINT,
 }
 _ibis_type_to_sqla.update(s_al._ibis_type_to_sqla)
+_ibis_type_to_sqla[dts.String] = sa.sql.sqltypes.String(length=3000)
 
 
 def _to_sqla_type(itype, type_map=None):

third_party/ibis/ibis_DB2/compiler.py

@@ -493,7 +493,8 @@ def _mod(t, expr):
 
 def _string_join(t, expr):
     sep, elements = expr.op().args
-    return sa.func.concat(*map(t.translate, elements))
+    columns = [col.name for col in map(t.translate, elements)]
+    return sa.sql.literal_column(" || ".join(columns))
 
 
 def _literal(t, expr):

third_party/ibis/ibis_DB2/expr/datatypes.py

@@ -148,7 +148,7 @@ def name(value):
 _TYPE_KEYS = tuple(_TYPE_RULES.keys())
 
 
-class TypeParser_Oracle(dt.TypeParser):
+class TypeParser_DB2(dt.TypeParser):
     def type(self) -> dt.DataType:
         if self._accept(Token_DB2.CLOB):
             return CLOB()

third_party/ibis/ibis_addon/operations.py

@@ -48,6 +48,13 @@
 from third_party.ibis.ibis_mssql.compiler import MSSQLExprTranslator
 from ibis.backends.postgres.compiler import PostgreSQLExprTranslator
 
+# avoid errors if Db2 is not installed and not needed
+try:
+    from third_party.ibis.ibis_DB2.compiler import DB2ExprTranslator
+except Exception:
+    DB2ExprTranslator = None
+
+
 # from third_party.ibis.ibis_snowflake.compiler import SnowflakeExprTranslator
 # from third_party.ibis.ibis_oracle.compiler import OracleExprTranslator <<<<<< DB2
 
@@ -213,6 +220,13 @@ def sa_format_hashbytes_oracle(translator, expr):
     hash_func = sa.func.standard_hash(compiled_arg, sa.sql.literal_column("'SHA256'"))
     return sa.func.lower(hash_func)
 
+def sa_format_hashbytes_db2(translator, expr):
+    arg, how = expr.op().args
+    compiled_arg = translator.translate(arg)
+    hashfunc = sa.func.hash(compiled_arg,sa.sql.literal_column("2"))
+    hex = sa.func.hex(hashfunc)
+    return sa.func.lower(hex)
+
 def sa_format_hashbytes_postgres(translator, expr):
     arg, how = expr.op().args
     compiled_arg = translator.translate(arg)
@@ -292,3 +306,6 @@ def sa_cast_postgres(t, expr):
 PostgreSQLExprTranslator._registry[RawSQL] = sa_format_raw_sql
 PostgreSQLExprTranslator._registry[ToChar] = sa_format_to_char
 PostgreSQLExprTranslator._registry[Cast] = sa_cast_postgres
+
+if DB2ExprTranslator: #check if Db2 driver is loaded
+    DB2ExprTranslator._registry[HashBytes] = sa_format_hashbytes_db2