- The INSERT...FROM SELECT construct now implies ``inline=True``

on :class:`.Insert`.  This helps to fix a bug where an
INSERT...FROM SELECT construct would inadvertently be compiled
as "implicit returning" on supporting backends, which would
cause breakage in the case of an INSERT that inserts zero rows
(as implicit returning expects a row), as well as arbitrary
return data in the case of an INSERT that inserts multiple
rows (e.g. only the first row of many).
A similar change is also applied to an INSERT..VALUES
with multiple parameter sets; implicit RETURNING will no longer emit
for this statement either.  As both of these constructs deal
with varible numbers of rows, the
:attr:`.ResultProxy.inserted_primary_key` accessor does not
apply.   Previously, there was a documentation note that one
may prefer ``inline=True`` with INSERT..FROM SELECT as some databases
don't support returning and therefore can't do "implicit" returning,
but there's no reason an INSERT...FROM SELECT needs implicit returning
in any case.   Regular explicit :meth:`.Insert.returning` should
be used to return variable numbers of result rows if inserted
data is needed.
fixes #3169

2 files changed, 24 insertions, 14 deletions

diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index e45510aa4..fac4980b0 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -1981,11 +1981,13 @@ class SQLCompiler(Compiled):
 
         need_pks = self.isinsert and \
             not self.inline and \
-            not stmt._returning
+            not stmt._returning and \
+            not stmt._has_multi_parameters
 
         implicit_returning = need_pks and \
             self.dialect.implicit_returning and \
             stmt.table.implicit_returning
+
         if self.isinsert:
             implicit_return_defaults = (implicit_returning and
                                         stmt._return_defaults)
diff --git a/lib/sqlalchemy/sql/dml.py b/lib/sqlalchemy/sql/dml.py
index f7e033d85..72dd92c99 100644
--- a/lib/sqlalchemy/sql/dml.py
+++ b/lib/sqlalchemy/sql/dml.py
@@ -269,6 +269,13 @@ class ValuesBase(UpdateBase):
          .. versionadded:: 0.8
              Support for multiple-VALUES INSERT statements.
 
+        .. versionchanged:: 1.0.0 an INSERT that uses a multiple-VALUES
+           clause, even a list of length one,
+           implies that the :paramref:`.Insert.inline` flag is set to
+           True, indicating that the statement will not attempt to fetch
+           the "last inserted primary key" or other defaults.  The statement
+           deals with an arbitrary number of rows, so the
+           :attr:`.ResultProxy.inserted_primary_key` accessor does not apply.
 
         .. seealso::
 
@@ -434,8 +441,13 @@ class Insert(ValuesBase):
          dynamically render the VALUES clause at execution time based on
          the parameters passed to :meth:`.Connection.execute`.
 
-        :param inline: if True, SQL defaults will be compiled 'inline' into
-         the statement and not pre-executed.
+        :param inline: if True, no attempt will be made to retrieve the
+         SQL-generated default values to be provided within the statement;
+         in particular,
+         this allows SQL expressions to be rendered 'inline' within the
+         statement without the need to pre-execute them beforehand; for
+         backends that support "returning", this turns off the "implicit
+         returning" feature for the statement.
 
         If both `values` and compile-time bind parameters are present, the
         compile-time bind parameters override the information specified
@@ -495,17 +507,12 @@ class Insert(ValuesBase):
          would normally raise an exception if these column lists don't
          correspond.
 
-        .. note::
-
-           Depending on backend, it may be necessary for the :class:`.Insert`
-           statement to be constructed using the ``inline=True`` flag; this
-           flag will prevent the implicit usage of ``RETURNING`` when the
-           ``INSERT`` statement is rendered, which isn't supported on a
-           backend such as Oracle in conjunction with an ``INSERT..SELECT``
-           combination::
-
-             sel = select([table1.c.a, table1.c.b]).where(table1.c.c > 5)
-             ins = table2.insert(inline=True).from_select(['a', 'b'], sel)
+        .. versionchanged:: 1.0.0 an INSERT that uses FROM SELECT
+           implies that the :paramref:`.Insert.inline` flag is set to
+           True, indicating that the statement will not attempt to fetch
+           the "last inserted primary key" or other defaults.  The statement
+           deals with an arbitrary number of rows, so the
+           :attr:`.ResultProxy.inserted_primary_key` accessor does not apply.
 
         .. note::
 
@@ -525,6 +532,7 @@ class Insert(ValuesBase):
             self._process_colparams(dict((n, Null()) for n in names))
 
         self.select_names = names
+        self.inline = True
         self.select = _interpret_as_select(select)
 
     def _copy_internals(self, clone=_clone, **kw):