feat: full snowflake support (#39)

Makefile

@@ -29,6 +29,7 @@ stubs:
 	stubgen sqlframe/bigquery/functions.py --output ./ --inspect-mode
 	stubgen sqlframe/duckdb/functions.py --output ./ --inspect-mode
 	stubgen sqlframe/postgres/functions.py --output ./ --inspect-mode
+	stubgen sqlframe/snowflake/functions.py --output ./ --inspect-mode
 
 package:
 	pip3 install wheel && python3 setup.py sdist bdist_wheel

docs/bigquery.md

@@ -385,7 +385,6 @@ print(session.catalog.listColumns(table_path))
 * [soundex](https://spark.apache.org/docs/latest/api/python/reference/pyspark.sql/api/pyspark.sql.functions.soundex.html)
 * [split](https://spark.apache.org/docs/latest/api/python/reference/pyspark.sql/api/pyspark.sql.functions.split.html)
     * Regular expressions not supported
-* [sqlglot_expression](https://spark.apache.org/docs/latest/api/python/reference/pyspark.sql/api/pyspark.sql.functions.sqlglot_expression.html)
 * [sqrt](https://spark.apache.org/docs/latest/api/python/reference/pyspark.sql/api/pyspark.sql.functions.sqrt.html)
 * [stddev](https://spark.apache.org/docs/latest/api/python/reference/pyspark.sql/api/pyspark.sql.functions.stddev.html)
 * [stddev_pop](https://spark.apache.org/docs/latest/api/python/reference/pyspark.sql/api/pyspark.sql.functions.stddev_pop.html)

sqlframe/base/column.py

@@ -251,6 +251,13 @@ def ensure_literal(cls, value) -> Column:
             return lit(value)
         return Column(value)
 
+    @property
+    def dtype(self) -> t.Optional[DataType]:
+        expression = self.expression.unalias()
+        if isinstance(expression, exp.Cast):
+            return expression.args.get("to")
+        return None
+
     def copy(self) -> Column:
         return Column(self.expression.copy())