Generalize RETURNING and suppor for MariaDB / SQLite

As almost every dialect supports RETURNING now, RETURNING
is also made more of a default assumption.

* the default compiler generates a RETURNING clause now
  when specified; CompileError is no longer raised.
* The dialect-level implicit_returning parameter now has
  no effect.   It's not fully clear if there are real world
  cases relying on the dialect-level parameter, so we will see
  once 2.0 is released.   ORM-level RETURNING can be disabled
  at the table level, and perhaps "implicit returning" should
  become an ORM-level option at some point as that's where
  it applies.
* Altered ORM update() / delete() to respect table-level
  implicit returning for fetch.
* Since MariaDB doesnt support UPDATE returning, "full_returning"
  is now split into insert_returning, update_returning, delete_returning
* Crazy new thing.  Dialects that have *both* cursor.lastrowid
  *and* returning.   so now we can pick between them for SQLite
  and mariadb.  so, we are trying to keep it on .lastrowid for
  simple inserts with an autoincrement column, this helps with
  some edge case test scenarios and i bet .lastrowid is faster
  anyway.  any return_defaults() / multiparams etc then we
  use returning
* SQLite decided they dont want to return rows that match in
  ON CONFLICT.  this is flat out wrong, but for now we need to
  work with it.

Fixes: #6195
Fixes: #7011
Closes: #7047
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/7047
Pull-request-sha: d25d5ea3abe094f282c53c7dd87f5f53a9e85248

Co-authored-by: Mike Bayer <mike_mp@zzzcomputing.com>
Change-Id: I9908ce0ff7bdc50bd5b27722081767c31c19a950

1 files changed, 26 insertions, 7 deletions

diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py
index bcbe83f3f..6b76601ff 100644
--- a/lib/sqlalchemy/engine/default.py
+++ b/lib/sqlalchemy/engine/default.py
@@ -57,6 +57,7 @@ from ..sql.compiler import DDLCompiler
 from ..sql.compiler import SQLCompiler
 from ..sql.elements import quoted_name
 from ..sql.schema import default_is_scalar
+from ..util.typing import Literal
 
 if typing.TYPE_CHECKING:
     from types import ModuleType
@@ -135,9 +136,11 @@ class DefaultDialect(Dialect):
     preexecute_autoincrement_sequences = False
     supports_identity_columns = False
     postfetch_lastrowid = True
+    favor_returning_over_lastrowid = False
     insert_null_pk_still_autoincrements = False
-    implicit_returning = False
-    full_returning = False
+    update_returning = False
+    delete_returning = False
+    insert_returning = False
     insert_executemany_returning = False
 
     cte_follows_insert = False
@@ -258,7 +261,7 @@ class DefaultDialect(Dialect):
         paramstyle: Optional[_ParamStyle] = None,
         isolation_level: Optional[_IsolationLevel] = None,
         dbapi: Optional[ModuleType] = None,
-        implicit_returning: Optional[bool] = None,
+        implicit_returning: Literal[True] = True,
         supports_native_boolean: Optional[bool] = None,
         max_identifier_length: Optional[int] = None,
         label_length: Optional[int] = None,
@@ -296,8 +299,6 @@ class DefaultDialect(Dialect):
             self.paramstyle = self.dbapi.paramstyle
         else:
             self.paramstyle = self.default_paramstyle
-        if implicit_returning is not None:
-            self.implicit_returning = implicit_returning
         self.positional = self.paramstyle in ("qmark", "format", "numeric")
         self.identifier_preparer = self.preparer(self)
         self._on_connect_isolation_level = isolation_level
@@ -324,6 +325,18 @@ class DefaultDialect(Dialect):
         self.label_length = label_length
         self.compiler_linting = compiler_linting
 
+    @util.deprecated_property(
+        "2.0",
+        "full_returning is deprecated, please use insert_returning, "
+        "update_returning, delete_returning",
+    )
+    def full_returning(self):
+        return (
+            self.insert_returning
+            and self.update_returning
+            and self.delete_returning
+        )
+
     @util.memoized_property
     def loaded_dbapi(self) -> ModuleType:
         if self.dbapi is None:
@@ -771,7 +784,6 @@ class StrCompileDialect(DefaultDialect):
     supports_sequences = True
     sequences_optional = True
     preexecute_autoincrement_sequences = False
-    implicit_returning = False
 
     supports_native_boolean = True
 
@@ -806,6 +818,8 @@ class DefaultExecutionContext(ExecutionContext):
 
     _soft_closed = False
 
+    _has_rowcount = False
+
     # a hook for SQLite's translation of
     # result column names
     # NOTE: pyhive is using this hook, can't remove it :(
@@ -1450,6 +1464,7 @@ class DefaultExecutionContext(ExecutionContext):
             # is testing this, and psycopg will no longer return
             # rowcount after cursor is closed.
             result.rowcount
+            self._has_rowcount = True
 
             row = result.fetchone()
             if row is not None:
@@ -1465,7 +1480,12 @@ class DefaultExecutionContext(ExecutionContext):
             # no results, get rowcount
             # (which requires open cursor on some drivers)
             result.rowcount
+            self._has_rowcount = True
             result._soft_close()
+        elif self.isupdate or self.isdelete:
+            result.rowcount
+            self._has_rowcount = True
+
         return result
 
     @util.memoized_property
@@ -1479,7 +1499,6 @@ class DefaultExecutionContext(ExecutionContext):
         getter = cast(
             SQLCompiler, self.compiled
         )._inserted_primary_key_from_lastrowid_getter
-
         lastrowid = self.get_lastrowid()
         return [getter(lastrowid, self.compiled_parameters[0])]