Compile and fix warning for regex in SQL action seq formatting (allen…

…ai#1864)

* compile regex

* replace the other regex too

allennlp/semparse/contexts/sql_context_utils.py

@@ -8,6 +8,8 @@
 from parsimonious.nodes import Node, NodeVisitor
 from parsimonious.grammar import Grammar
 
+WHITESPACE_REGEX = re.compile(" wsp |wsp | wsp| ws |ws | ws")
+
 def format_grammar_string(grammar_dictionary: Dict[str, List[str]]) -> str:
     """
     Formats a dictionary of production rules into the string format expected
@@ -98,7 +100,7 @@ def format_action(nonterminal: str,
 
     else:
         right_hand_side = right_hand_side.lstrip("(").rstrip(")")
-        child_strings = [token for token in re.split(" wsp |wsp | wsp| ws |ws | ws|", right_hand_side) if token]
+        child_strings = [token for token in WHITESPACE_REGEX.split(right_hand_side) if token]
         child_strings = [tok.upper() if tok.upper() in keywords_to_uppercase else tok for tok in child_strings]
         return f"{nonterminal} -> [{', '.join(child_strings)}]"
 
@@ -175,8 +177,7 @@ def add_action(self, node: Node) -> None:
                     else:
                         child_right_side_string = child.expr._as_rhs().lstrip("(").rstrip(")") # pylint: disable=protected-access
                         child_right_side_list = [tok for tok in
-                                                 re.split(" wsp |wsp | wsp| ws |ws | ws|",
-                                                          child_right_side_string) if tok]
+                                                 WHITESPACE_REGEX.split(child_right_side_string) if tok]
                         child_right_side_list = [tok.upper() if tok.upper() in
                                                  self.keywords_to_uppercase else tok
                                                  for tok in child_right_side_list]