Fixed #3214 -- Stopped parsing SQL with regex.

Avoided introducing a new regex-based SQL splitter in the migrations
framework, before we're bound by backwards compatibility.

Adapted this change to the legacy "initial SQL data" feature, even
though it's already deprecated, in order to facilitate the transition
to migrations.

sqlparse becomes mandatory for RunSQL on some databases (all but
PostgreSQL). There's no API to provide a single statement and tell
Django not to attempt splitting. Since we have a more robust splitting
implementation, that seems like a good tradeoff. It's easier to add a
new keyword argument later if necessary than to remove one.

Many people contributed to both tickets, thank you all, and especially
Claude for the review.

Refs #22401.

django/db/migrations/operations/special.py

@@ -1,4 +1,3 @@
-import re
 from .base import Operation
 
 
@@ -43,20 +42,16 @@ class SeparateDatabaseAndState(Operation):
 
 class RunSQL(Operation):
     """
-    Runs some raw SQL - a single statement by default, but it will attempt
-    to parse and split it into multiple statements if multiple=True.
-
-    A reverse SQL statement may be provided.
+    Runs some raw SQL. A reverse SQL statement may be provided.
 
     Also accepts a list of operations that represent the state change effected
     by this SQL change, in case it's custom column/table creation/deletion.
     """
 
-    def __init__(self, sql, reverse_sql=None, state_operations=None, multiple=False):
+    def __init__(self, sql, reverse_sql=None, state_operations=None):
         self.sql = sql
         self.reverse_sql = reverse_sql
         self.state_operations = state_operations or []
-        self.multiple = multiple
 
     @property
     def reversible(self):
@@ -66,30 +61,15 @@ class RunSQL(Operation):
         for state_operation in self.state_operations:
             state_operation.state_forwards(app_label, state)
 
-    def _split_sql(self, sql):
-        regex = r"(?mx) ([^';]* (?:'[^']*'[^';]*)*)"
-        comment_regex = r"(?mx) (?:^\s*$)|(?:--.*$)"
-        # First, strip comments
-        sql = "\n".join([x.strip().replace("%", "%%") for x in re.split(comment_regex, sql) if x.strip()])
-        # Now get each statement
-        for st in re.split(regex, sql)[1:][::2]:
-            yield st
-
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        if self.multiple:
-            statements = self._split_sql(self.sql)
-        else:
-            statements = [self.sql]
+        statements = schema_editor.connection.ops.prepare_sql_script(self.sql)
         for statement in statements:
             schema_editor.execute(statement)
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
         if self.reverse_sql is None:
             raise NotImplementedError("You cannot reverse this operation")
-        if self.multiple:
-            statements = self._split_sql(self.reverse_sql)
-        else:
-            statements = [self.reverse_sql]
+        statements = schema_editor.connection.ops.prepare_sql_script(self.reverse_sql)
         for statement in statements:
             schema_editor.execute(statement)