Deprecate create_engine.implicit_returning

The :paramref:`_sa.create_engine.implicit_returning` parameter is
deprecated on the :func:`_sa.create_engine` function only; the parameter
remains available on the :class:`_schema.Table` object. This parameter was
originally intended to enable the "implicit returning" feature of
SQLAlchemy when it was first developed and was not enabled by default.
Under modern use, there's no reason this parameter should be disabled, and
it has been observed to cause confusion as it degrades performance and
makes it more difficult for the ORM to retrieve recently inserted server
defaults. The parameter remains available on :class:`_schema.Table` to
specifically suit database-level edge cases which make RETURNING
infeasible, the sole example currently being SQL Server's limitation that
INSERT RETURNING may not be used on a table that has INSERT triggers on it.

Also removed from the Oracle dialect some logic that would upgrade
an Oracle 8/8i server version to use implicit returning if the
parameter were explictly passed; these versions of Oracle
still support RETURNING so the feature is now enabled for all
Oracle versions.

Fixes: #6962
Change-Id: Ib338e300cd7c8026c3083043f645084a8211aed8

1 files changed, 24 insertions, 7 deletions

diff --git a/lib/sqlalchemy/testing/assertsql.py b/lib/sqlalchemy/testing/assertsql.py
index ca0bc6726..9816c99b7 100644
--- a/lib/sqlalchemy/testing/assertsql.py
+++ b/lib/sqlalchemy/testing/assertsql.py
@@ -186,7 +186,9 @@ class CompiledSQL(SQLMatchRule):
             self.is_consumed = True
             self.errormessage = None
         else:
-            self.errormessage = self._failure_message(params) % {
+            self.errormessage = self._failure_message(
+                execute_observed, params
+            ) % {
                 "received_statement": _received_statement,
                 "received_parameters": _received_parameters,
             }
@@ -203,7 +205,7 @@ class CompiledSQL(SQLMatchRule):
         else:
             return None
 
-    def _failure_message(self, expected_params):
+    def _failure_message(self, execute_observed, expected_params):
         return (
             "Testing for compiled statement\n%r partial params %s, "
             "received\n%%(received_statement)r with params "
@@ -223,7 +225,7 @@ class RegexSQL(CompiledSQL):
         self.params = params
         self.dialect = dialect
 
-    def _failure_message(self, expected_params):
+    def _failure_message(self, execute_observed, expected_params):
         return (
             "Testing for compiled statement ~%r partial params %s, "
             "received %%(received_statement)r with params "
@@ -263,11 +265,8 @@ class DialectSQL(CompiledSQL):
 
         return received_stmt, execute_observed.context.compiled_parameters
 
-    def _compare_sql(self, execute_observed, received_statement):
+    def _dialect_adjusted_statement(self, paramstyle):
         stmt = re.sub(r"[\n\t]", "", self.statement)
-        # convert our comparison statement to have the
-        # paramstyle of the received
-        paramstyle = execute_observed.context.dialect.paramstyle
         if paramstyle == "pyformat":
             stmt = re.sub(r":([\w_]+)", r"%(\1)s", stmt)
         else:
@@ -280,9 +279,27 @@ class DialectSQL(CompiledSQL):
             elif paramstyle == "numeric":
                 repl = None
             stmt = re.sub(r":([\w_]+)", repl, stmt)
+        return stmt
 
+    def _compare_sql(self, execute_observed, received_statement):
+        paramstyle = execute_observed.context.dialect.paramstyle
+        stmt = self._dialect_adjusted_statement(paramstyle)
         return received_statement == stmt
 
+    def _failure_message(self, execute_observed, expected_params):
+        paramstyle = execute_observed.context.dialect.paramstyle
+        return (
+            "Testing for compiled statement\n%r partial params %s, "
+            "received\n%%(received_statement)r with params "
+            "%%(received_parameters)r"
+            % (
+                self._dialect_adjusted_statement(paramstyle).replace(
+                    "%", "%%"
+                ),
+                repr(expected_params).replace("%", "%%"),
+            )
+        )
+
 
 class CountStatements(AssertRule):
     def __init__(self, count):