Use cx_Oracle dml_ret_array_val

Fixed issue for cx_Oracle 7.0 where the behavior of Oracle param.getvalue()
now returns a list, rather than a single scalar value, breaking
autoincrement logic throughout the Core and ORM. The dml_ret_array_val
compatibility flag is used for cx_Oracle 6.3 and 6.4 to establish compatible
behavior with 7.0 and forward, for cx_Oracle 6.2.1 and prior a version
number check falls back to the old logic.

Fixes: #4335
Change-Id: Ia60f5514803a505898c1ac9252355990c6203dda

doc/build/changelog/unreleased_12/4335.rst

@@ -0,0 +1,11 @@
+.. change::
+   :tags: bug, oracle
+   :tickets: 4335
+
+   Fixed issue for cx_Oracle 7.0 where the behavior of Oracle param.getvalue()
+   now returns a list, rather than a single scalar value, breaking
+   autoincrement logic throughout the Core and ORM. The dml_ret_array_val
+   compatibility flag is used for cx_Oracle 6.3 and 6.4 to establish compatible
+   behavior with 7.0 and forward, for cx_Oracle 6.2.1 and prior a version
+   number check falls back to the old logic.
+

lib/sqlalchemy/dialects/oracle/cx_oracle.py

@@ -609,7 +609,9 @@ def create_cursor(self):
     def get_result_proxy(self):
         if self.out_parameters and self.compiled.returning:
             returning_params = [
-                self.out_parameters["ret_%d" % i].getvalue()
+                self.dialect._returningval(
+                    self.out_parameters["ret_%d" % i]
+                )
                 for i in range(len(self.out_parameters))
             ]
             return ReturningResultProxy(self, returning_params)
@@ -633,13 +635,15 @@ def get_result_proxy(self):
                         if result_processor is not None:
                             out_parameters[name] = \
                                 result_processor(
-                                    self.out_parameters[name].getvalue())
+                                    self.dialect._paramval(
+                                        self.out_parameters[name]
+                                    ))
                         else:
-                            out_parameters[name] = self.out_parameters[
-                                name].getvalue()
+                            out_parameters[name] = self.dialect._paramval(
+                                self.out_parameters[name])
             else:
                 result.out_parameters = dict(
-                                            (k, v.getvalue())
+                                            (k, self._dialect._paramval(v))
                     for k, v in self.out_parameters.items()
                 )
 
@@ -744,6 +748,24 @@ def __init__(self,
                 _OracleInteger, _OracleBINARY_FLOAT, _OracleBINARY_DOUBLE
             }
 
+            self._paramval = lambda value: value.getvalue()
+
+            # https://github.com/oracle/python-cx_Oracle/issues/176#issuecomment-386821291
+            # https://github.com/oracle/python-cx_Oracle/issues/224
+            self._values_are_lists = self.cx_oracle_ver >= (6, 3)
+            if self._values_are_lists:
+                cx_Oracle.__future__.dml_ret_array_val = True
+
+                def _returningval(value):
+                    try:
+                        return value.values[0][0]
+                    except IndexError:
+                        return None
+
+                self._returningval = _returningval
+            else:
+                self._returningval = self._paramval
+
         self._is_cx_oracle_6 = self.cx_oracle_ver >= (6, )
 
     def _pop_deprecated_kwargs(self, kwargs):

tox.ini

@@ -23,7 +23,8 @@ deps=pytest
      mysql: pymysql
      mysql: mysql-connector-python
      # waiting for https://github.com/oracle/python-cx_Oracle/issues/75
-     oracle: cx_oracle>=6.0.2,!=6.3,!=6.4
+     oracle: cx_oracle>=7.0
+     oracle6: cx_oracle>=6.0.2,!=6.3,!=6.4,<7.0
      oracle5: cx_oracle==5.2.1
      mssql: pyodbc
      mssql: pymssql
@@ -51,16 +52,16 @@ setenv=
     BASECOMMAND=python -m pytest --log-info=sqlalchemy.testing
 
     WORKERS={env:TOX_WORKERS:-n4}
-    oracle,oracle5: WORKERS={env:TOX_WORKERS:-n2}
+    oracle,oracle6,oracle5: WORKERS={env:TOX_WORKERS:-n2}
     nocext: DISABLE_SQLALCHEMY_CEXT=1
     cov: COVERAGE={[testenv]cov_args}
     sqlite: SQLITE={env:TOX_SQLITE:--db sqlite}
     postgresql: POSTGRESQL={env:TOX_POSTGRESQL:--db postgresql}
     mysql: MYSQL={env:TOX_MYSQL:--db mysql --db pymysql}
-    oracle,oracle5: ORACLE={env:TOX_ORACLE:--db oracle}
+    oracle,oracle6,oracle5: ORACLE={env:TOX_ORACLE:--db oracle}
     mssql: MSSQL={env:TOX_MSSQL:--db mssql --db mssql_pymssql}
-    oracle,oracle5,mssql: IDENTS=--write-idents db_idents.txt
-    oracle,oracle5,mssql: NOMEMORY=--nomemory
+    oracle,oracle6,oracle5,mssql: IDENTS=--write-idents db_idents.txt
+    oracle,oracle6,oracle5,mssql: NOMEMORY=--nomemory
     backendonly: BACKENDONLY=--backend-only
 
 # tox as of 2.0 blocks all environment variables from the
@@ -72,7 +73,7 @@ passenv=ORACLE_HOME NLS_LANG TOX_POSTGRESQL TOX_MYSQL TOX_ORACLE TOX_MSSQL TOX_S
 commands=
   nocext: sh -c "rm -f lib/sqlalchemy/*.so"
   {env:BASECOMMAND} {env:WORKERS} {env:SQLITE:} {env:POSTGRESQL:} {env:MYSQL:} {env:ORACLE:} {env:MSSQL:} {env:BACKENDONLY:} {env:IDENTS:} {env:NOMEMORY:} {env:COVERAGE:} {posargs}
-  oracle,oracle5,mssql: python reap_dbs.py db_idents.txt
+  oracle,oracle6,oracle5,mssql: python reap_dbs.py db_idents.txt
 
 [testenv:pep8]
 deps=flake8