perf: speedup QB field sanitization (#28818)

frappe/database/query.py

@@ -1,5 +1,6 @@
 import re
 from ast import literal_eval
+from functools import lru_cache
 from types import BuiltinFunctionType
 from typing import TYPE_CHECKING, TypeAlias
 
@@ -275,19 +276,13 @@ class Engine:
 			return Function(func, *_args, alias=alias or None)
 
 	def sanitize_fields(self, fields: str | list | tuple):
-		def _sanitize_field(field: str):
-			if not isinstance(field, str):
-				return field
-			stripped_field = sqlparse.format(field, strip_comments=True, keyword_case="lower")
-			if self.is_mariadb:
-				return MARIADB_SPECIFIC_COMMENT.sub("", stripped_field)
-			return stripped_field
-
 		if isinstance(fields, list | tuple):
-			return [_sanitize_field(field) for field in fields]
+			return [
+				_sanitize_field(field, self.is_mariadb) if isinstance(field, str) else field
+				for field in fields
+			]
 		elif isinstance(fields, str):
-			return _sanitize_field(fields)
-
+			return _sanitize_field(fields, self.is_mariadb)
 		return fields
 
 	def parse_string_field(self, field: str):
@@ -524,7 +519,7 @@ def literal_eval_(literal):
 def has_function(field):
 	_field = field.casefold() if (isinstance(field, str) and "`" not in field) else field
 	if not issubclass(type(_field), Criterion):
-		if any([f"{func}(" in _field for func in SQL_FUNCTIONS]):
+		if any([f"{func}(" in _field for func in SQL_FUNCTIONS]):  # ) <- ignore this comment.
 			return True
 
 
@@ -558,3 +553,15 @@ def get_nested_set_hierarchy_result(doctype: str, name: str, hierarchy: str) ->
 			.run(pluck=True)
 		)
 	return result
+
+
+@lru_cache(maxsize=1024)
+def _sanitize_field(field: str, is_mariadb):
+	if field == "*" or not SPECIAL_CHAR_PATTERN.match(field):
+		# Skip checking if there are no special characters
+		return field
+
+	stripped_field = sqlparse.format(field, strip_comments=True, keyword_case="lower")
+	if is_mariadb:
+		return MARIADB_SPECIFIC_COMMENT.sub("", stripped_field)
+	return stripped_field

frappe/database/schema.py

@@ -5,7 +5,9 @@ from frappe import _
 from frappe.utils import cint, cstr, flt
 from frappe.utils.defaults import get_not_null_defaults
 
+# This matches anything that isn't [a-zA-Z0-9_]
 SPECIAL_CHAR_PATTERN = re.compile(r"[\W]", flags=re.UNICODE)
+
 VARCHAR_CAST_PATTERN = re.compile(r"varchar\(([\d]+)\)")