SNOW-652674: normalize name and denormalize name should handle empty string (#349)

Author: sfc-gh-aling

DESCRIPTION.md

@@ -9,6 +9,9 @@ Source code is also available at:
 
 # Release Notes
 
+- v1.4.3(Unreleased)
+  - Fixed a bug that `SnowflakeDialect.normalize_name` and `SnowflakeDialect.denormalize_name` could not handle empty string.
+
 - v1.4.2(Sep 19, 2022)
 
   - Improved performance by standardizing string interpolations to f-strings.

setup.cfg

@@ -3,7 +3,7 @@ universal = 1
 
 [metadata]
 name = snowflake-sqlalchemy
-version = 1.4.2
+version = 1.4.3
 description = Snowflake SQLAlchemy Dialect
 long_description = file: DESCRIPTION.md
 long_description_content_type = text/markdown

src/snowflake/sqlalchemy/snowdialect.py

@@ -252,6 +252,8 @@ def _has_object(self, connection, object_type, object_name, schema=None):
     def normalize_name(self, name):
         if name is None:
             return None
+        if name == "":
+            return ""
         if name.upper() == name and not self.identifier_preparer._requires_quotes(
             name.lower()
         ):
@@ -264,6 +266,8 @@ def normalize_name(self, name):
     def denormalize_name(self, name):
         if name is None:
             return None
+        if name == "":
+            return ""
         elif name.lower() == name and not self.identifier_preparer._requires_quotes(
             name.lower()
         ):

tests/test_core.py

@@ -1718,3 +1718,44 @@ def test_result_type_and_value(engine_testaccount):
         assert data is not None
         data = json.loads(results[-1][29])
         assert data[1]["k"] == 2
+
+
+def test_normalize_and_denormalize_empty_string_column_name(engine_testaccount):
+    with engine_testaccount.connect() as conn:
+        table_name = random_string(5)
+        conn.exec_driver_sql(
+            f"""
+CREATE OR REPLACE TEMP TABLE {table_name}
+(EMPID INT, DEPT TEXT, JAN INT, FEB INT)
+"""
+        )
+        conn.exec_driver_sql(
+            f"""
+INSERT INTO {table_name} VALUES
+    (1, 'ELECTRONICS', 100, 200),
+    (2, 'CLOTHES', 100, 300)
+"""
+        )
+        results = conn.exec_driver_sql(
+            f'SELECT * FROM {table_name} UNPIVOT(SALES FOR "" IN (JAN, FEB)) ORDER BY EMPID;'
+        ).fetchall()  # normalize_name will be called
+        assert results == [
+            (1, "ELECTRONICS", "JAN", 100),
+            (1, "ELECTRONICS", "FEB", 200),
+            (2, "CLOTHES", "JAN", 100),
+            (2, "CLOTHES", "FEB", 300),
+        ]
+
+        conn.exec_driver_sql(
+            f"""
+CREATE OR REPLACE TEMP TABLE {table_name}
+(COL INT, "" INT)
+"""
+        )
+        inspector = inspect(conn)
+        columns = inspector.get_columns(table_name)  # denormalize_name will be called
+        assert (
+            len(columns) == 2
+            and columns[0]["name"] == "col"
+            and columns[1]["name"] == ""
+        )