Revise psycopg2 execute_values approach

Revised the approach for the just added support for the psycopg2
"execute_values()" feature added in 1.3.7 for :ticket:`4623`.  The approach
relied upon a regular expression that would fail to match for a more
complex INSERT statement such as one which had subqueries involved.   The
new approach matches exactly the string that was rendered as the VALUES
clause.

Fixes: #4623
Change-Id: Icaae0f7b6bcf87a2cf5c6290a839c8429dd5fac3

2 files changed, 22 insertions, 6 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/psycopg2.py b/lib/sqlalchemy/dialects/postgresql/psycopg2.py
index 26014dadc..1a4db1108 100644
--- a/lib/sqlalchemy/dialects/postgresql/psycopg2.py
+++ b/lib/sqlalchemy/dialects/postgresql/psycopg2.py
@@ -849,8 +849,6 @@ class PGDialect_psycopg2(PGDialect):
         else:
             return None
 
-    _insert_values_match = re.compile(r".* VALUES (\(.+\))").match
-
     def do_executemany(self, cursor, statement, parameters, context=None):
         if self.executemany_mode is EXECUTEMANY_DEFAULT:
             cursor.executemany(statement, parameters)
@@ -860,8 +858,14 @@ class PGDialect_psycopg2(PGDialect):
             self.executemany_mode is EXECUTEMANY_VALUES
             and context
             and context.isinsert
+            and context.compiled.insert_single_values_expr
         ):
-            executemany_values = self._insert_values_match(statement)
+            executemany_values = (
+                "(%s)" % context.compiled.insert_single_values_expr
+            )
+            # guard for statement that was altered via event hook or similar
+            if executemany_values not in statement:
+                executemany_values = None
         else:
             executemany_values = None
 
@@ -870,7 +874,7 @@ class PGDialect_psycopg2(PGDialect):
             # into executemany(), since no DBAPI has ever supported that
             # until the introduction of psycopg2's executemany_values, so
             # we are not yet using the fetch=True flag.
-            statement = statement.replace(executemany_values.group(1), "%s")
+            statement = statement.replace(executemany_values, "%s")
             if self.executemany_values_page_size:
                 kwargs = {"page_size": self.executemany_values_page_size}
             else:
@@ -879,7 +883,7 @@ class PGDialect_psycopg2(PGDialect):
                 cursor,
                 statement,
                 parameters,
-                template=executemany_values.group(1),
+                template=executemany_values,
                 **kwargs
             )
 
diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index 8bd2249e2..fa7eeaecf 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -498,6 +498,15 @@ class SQLCompiler(Compiled):
 
     """
 
+    insert_single_values_expr = None
+    """When an INSERT is compiled with a single set of parameters inside
+    a VALUES expression, the string is assigned here, where it can be
+    used for insert batching schemes to rewrite the VALUES expression.
+
+    .. versionadded:: 1.3.8
+
+    """
+
     insert_prefetch = update_prefetch = ()
 
     def __init__(
@@ -2512,7 +2521,10 @@ class SQLCompiler(Compiled):
                 )
             )
         else:
-            text += " VALUES (%s)" % ", ".join([c[1] for c in crud_params])
+            insert_single_values_expr = ", ".join([c[1] for c in crud_params])
+            text += " VALUES (%s)" % insert_single_values_expr
+            if toplevel:
+                self.insert_single_values_expr = insert_single_values_expr
 
         if insert_stmt._post_values_clause is not None:
             post_values_clause = self.process(