Add mogrify method to cursor to evaluate full query (#28)

* Add mogrify method to cursor to evaluate full query

* Use DefaultDialect definition of unicode items

* Support JSON type

* Allow support multi-value inserts

* JSON/VARIANT are same thing

* No cascade on Drop Schema

Author: rad-pat

databend_sqlalchemy/connector.py

@@ -165,10 +165,15 @@ def description(self):
     def close(self):
         self._reset_state()
 
+    def mogrify(self, query, parameters):
+        if parameters:
+            query = query % _escaper.escape_args(parameters)
+        return query
+
     def execute(self, operation, parameters=None, is_response=True):
         """Prepare and execute a database operation (query or command)."""
 
-        #ToDo - Fix this, which is preventing the execution of blank DDL sunch as CREATE INDEX statements which aren't suppoorted
+        #ToDo - Fix this, which is preventing the execution of blank DDL sunch as CREATE INDEX statements which aren't currently supported
         # Seems hard to fix when statements are coming from metadata.create_all()
         if operation == "":
             return
@@ -179,11 +184,7 @@ def execute(self, operation, parameters=None, is_response=True):
         self._uuid = uuid.uuid1()
 
         try:
-            # operation = operation.replace('%%', '%')
-            if parameters:
-                query = operation % _escaper.escape_args(parameters)
-            else:
-                query = operation
+            query = self.mogrify(operation, parameters)
             query = query.replace('%%', '%')
             if is_response:
                 rows = self._db.query_iter(query)

databend_sqlalchemy/databend_dialect.py

@@ -128,6 +128,7 @@ def process(value):
     "array": ARRAY,
     "map": MAP,
     "json": JSON,
+    "variant": JSON,
     "varchar": VARCHAR,
     "boolean": BOOLEAN,
     "binary": BINARY,
@@ -259,6 +260,9 @@ def visit_NUMERIC(self, type_, **kw):
     def visit_NVARCHAR(self, type_, **kw):
         return self.visit_VARCHAR(type_, **kw)
 
+    def visit_JSON(self, type_, **kw):
+        return "JSON"  # or VARIANT
+
 
 class DatabendDDLCompiler(compiler.DDLCompiler):
 
@@ -279,13 +283,16 @@ def visit_create_index(self, create, include_schema=False, include_table_schema=
     def visit_drop_index(self, drop, **kw):
         return ""
 
+    def visit_drop_schema(self, drop, **kw):
+        # Override - Databend does not support the CASCADE option
+        schema = self.preparer.format_schema(drop.element)
+        return "DROP SCHEMA " + schema
+
 
 class DatabendDialect(default.DefaultDialect):
     name = "databend"
     driver = "databend"
     supports_cast = True
-    supports_unicode_statements = True
-    supports_unicode_binds = True
     supports_sane_rowcount = False
     supports_sane_multi_rowcount = False
     supports_native_boolean = True
@@ -294,6 +301,7 @@ class DatabendDialect(default.DefaultDialect):
     supports_comments = False
     supports_empty_insert = False
     supports_is_distinct_from = False
+    supports_multivalues_insert = True
 
     supports_statement_cache = False
     supports_server_side_cursors = True
@@ -302,8 +310,6 @@ class DatabendDialect(default.DefaultDialect):
     default_paramstyle = "pyformat"
     colspecs = colspecs
     ischema_names = ischema_names
-    convert_unicode = True
-    returns_unicode_strings = True
     returns_native_bytes = True
     div_is_floordiv = False
     description_encoding = None
@@ -319,10 +325,16 @@ class DatabendDialect(default.DefaultDialect):
     _backslash_escapes = True
 
     def __init__(
-            self, context: Optional[ExecutionContext] = None, *args: Any, **kwargs: Any
+            self,
+            context: Optional[ExecutionContext] = None,
+            json_serializer=None,
+            json_deserializer=None,
+            *args: Any, **kwargs: Any
     ):
         super(DatabendDialect, self).__init__(*args, **kwargs)
         self.context: Union[ExecutionContext, Dict] = context or {}
+        self._json_serializer = json_serializer
+        self._json_deserializer = json_deserializer
 
     @classmethod
     def dbapi(cls):

databend_sqlalchemy/requirements.py

@@ -175,7 +175,7 @@ def precision_generic_float_type(self):
         least seven decimal places when using the generic Float type.
 
         """
-        return exclusions.closed()  # I couldn't get the test for this one working, maybe when the driver returns a python decimal?
+        return exclusions.closed()  #ToDo - I couldn't get the test for this one working, not sure where the issue is - AssertionError: {Decimal('15.7563829')} != {Decimal('15.7563827')}
 
     @property
     def array_type(self):
@@ -186,3 +186,9 @@ def float_is_numeric(self):
         """target backend uses Numeric for Float/Dual"""
 
         return exclusions.closed()
+
+    @property
+    def json_type(self):
+        """target platform implements a native JSON type."""
+
+        return exclusions.closed()  #ToDo - This could be enabled if primary keys were supported