Fix crash on quoted anonymous function names

sql_metadata/column_extractor.py

@@ -135,7 +135,7 @@ def _is_date_part_unit(node: exp.Column) -> bool:
     parent = node.parent
     if (
         isinstance(parent, exp.Anonymous)
-        and parent.this.lower() in _DATE_PART_FUNCTIONS
+        and parent.name.lower() in _DATE_PART_FUNCTIONS
     ):
         exprs = parent.expressions
         return len(exprs) > 0 and exprs[0] is node

test/test_getting_columns.py

@@ -708,6 +708,22 @@ def test_dateadd_unit_not_column():
     assert parser.columns_dict == {"select": ["DateReleased"]}
 
 
+def test_quoted_anonymous_function_name():
+    # solved: https://github.com/macbre/sql-metadata/issues/688
+    # a quoted function name is an Identifier, not a str, in sqlglot's AST
+    query = """
+    SELECT date_trunc('DAY', "timezone"('UTC', tbl.data_timestamp))
+    FROM tbl
+    """
+    parser = Parser(query)
+    assert parser.tables == ["tbl"]
+    assert parser.columns == ["tbl.data_timestamp"]
+
+    # date-part unit is still skipped when the function name is quoted
+    parser = Parser('SELECT "dateadd"(dd, 30, DateReleased) FROM test')
+    assert parser.tables == ["test"]
+    assert parser.columns == ["DateReleased"]
+
 def test_backtick_column_with_operation():
     # solved: https://github.com/macbre/sql-metadata/issues/448
     query = "SELECT `col1 with space` / `col2_anything` FROM table1"