feat: support ALTER TABLE .. SET COMMENT

fakesnow/fakes.py

@@ -151,7 +151,7 @@ def execute(
 
         sql = transformed.sql(dialect="duckdb")
 
-        if cmd != "COMMENT TABLE":
+        if cmd not in ("COMMENT TABLE", "ALTERTABLE"):
             try:
                 self._last_sql = sql
                 self._last_params = params

fakesnow/transforms.py

@@ -124,6 +124,19 @@ def extract_comment(expression: exp.Expression) -> exp.Expression:
         new = expression.copy()
         new.args["table_comment"] = cexp.this
         return new
+    elif (
+        isinstance(expression, exp.AlterTable)
+        and (sexp := expression.find(exp.Set))
+        and not sexp.args["tag"]
+        and (eq := sexp.find(exp.EQ))
+        and (id := eq.find(exp.Identifier))
+        and isinstance(id.this, str)
+        and id.this.upper() == "COMMENT"
+        and (lit := eq.find(exp.Literal))
+    ):
+        new = expression.copy()
+        new.args["table_comment"] = lit.this
+        return new
 
     return expression
 

tests/test_fakes.py

@@ -449,6 +449,8 @@ def read_comment() -> str:
     assert read_comment() == "pepperoni"
     cur.execute("COMMENT IF EXISTS ON TABLE schema1.ingredients IS 'mushrooms'")
     assert read_comment() == "mushrooms"
+    cur.execute("ALTER TABLE ingredients SET comment = 'pineapple'")
+    assert read_comment() == "pineapple"
 
 
 def test_tags_noop(cur: snowflake.connector.cursor.SnowflakeCursor):

tests/test_transforms.py

@@ -55,6 +55,10 @@ def test_extract_comment() -> None:
     assert e.sql() == "COMMENT ON TABLE table1 IS 'comment1'"
     assert e.args["table_comment"] == "comment1"
 
+    e = sqlglot.parse_one("ALTER TABLE table1 SET COMMENT = 'comment1'", read="snowflake").transform(extract_comment)
+    assert e.sql() == "ALTER TABLE table1 SET COMMENT = 'comment1'"
+    assert e.args["table_comment"] == "comment1"
+
 
 def test_float_to_double() -> None:
     assert (