Default psycopg2 executemany mode to "values_only"

The psycopg2 dialect now defaults to using the very performant
``execute_values()`` psycopg2 extension for compiled INSERT statements,
and also impements RETURNING support when this extension is used.  This
allows INSERT statements that even include an autoincremented SERIAL
or IDENTITY value to run very fast while still being able to return the
newly generated primary key values.   The ORM will then integrate this
new feature in a separate change.

Implements RETURNING for insert with executemany

Adds support to return_defaults() mode and inserted_primary_key
to support mutiple INSERTed rows, via return_defauls_rows
and inserted_primary_key_rows accessors.

within default execution context, new cached compiler
getters are used to fetch primary keys from rows

inserted_primary_key now returns a plain tuple. this
is not yet a row-like object however this can be
added.

Adds distinct "values_only" and "batch" modes, as
"values" has a lot of benefits but "batch" breaks
cursor.rowcount

psycopg2 minimum version 2.7 so we can remove the
large number of checks for very old versions of
psycopg2

simplify tests to no longer distinguish between
native and non-native json

Fixes: #5401
Change-Id: Ic08fd3423d4c5d16ca50994460c0c234868bd61c

1 files changed, 84 insertions, 10 deletions

diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index 61178291a..e09e60c2c 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -676,13 +676,15 @@ class SQLCompiler(Compiled):
 
     """
 
+    inline = False
+
     def __init__(
         self,
         dialect,
         statement,
         cache_key=None,
         column_keys=None,
-        inline=False,
+        for_executemany=False,
         linting=NO_LINTING,
         **kwargs
     ):
@@ -695,8 +697,13 @@ class SQLCompiler(Compiled):
         :param column_keys:  a list of column names to be compiled into an
          INSERT or UPDATE statement.
 
-        :param inline: whether to generate INSERT statements as "inline", e.g.
-         not formatted to return any generated defaults
+        :param for_executemany: whether INSERT / UPDATE statements should
+         expect that they are to be invoked in an "executemany" style,
+         which may impact how the statement will be expected to return the
+         values of defaults and autoincrement / sequences and similar.
+         Depending on the backend and driver in use, support for retreiving
+         these values may be disabled which means SQL expressions may
+         be rendered inline, RETURNING may not be rendered, etc.
 
         :param kwargs: additional keyword arguments to be consumed by the
          superclass.
@@ -709,9 +716,10 @@ class SQLCompiler(Compiled):
         if cache_key:
             self._cache_key_bind_match = {b: b for b in cache_key[1]}
 
-        # compile INSERT/UPDATE defaults/sequences inlined (no pre-
-        # execute)
-        self.inline = inline or getattr(statement, "_inline", False)
+        # compile INSERT/UPDATE defaults/sequences to expect executemany
+        # style execution, which may mean no pre-execute of defaults,
+        # or no RETURNING
+        self.for_executemany = for_executemany
 
         self.linting = linting
 
@@ -755,10 +763,21 @@ class SQLCompiler(Compiled):
 
         Compiled.__init__(self, dialect, statement, **kwargs)
 
-        if (
-            self.isinsert or self.isupdate or self.isdelete
-        ) and statement._returning:
-            self.returning = statement._returning
+        if self.isinsert or self.isupdate or self.isdelete:
+            if statement._returning:
+                self.returning = statement._returning
+
+            if self.isinsert or self.isupdate:
+                if statement._inline:
+                    self.inline = True
+                elif self.for_executemany and (
+                    not self.isinsert
+                    or (
+                        self.dialect.insert_executemany_returning
+                        and statement._return_defaults
+                    )
+                ):
+                    self.inline = True
 
         if self.positional and self._numeric_binds:
             self._apply_numbered_params()
@@ -1088,6 +1107,61 @@ class SQLCompiler(Compiled):
             self._result_columns
         )
 
+    @util.memoized_property
+    def _inserted_primary_key_from_lastrowid_getter(self):
+        key_getter = self._key_getters_for_crud_column[2]
+        table = self.statement.table
+
+        getters = [
+            (operator.methodcaller("get", key_getter(col), None), col)
+            for col in table.primary_key
+        ]
+
+        autoinc_col = table._autoincrement_column
+        if autoinc_col is not None:
+            # apply type post processors to the lastrowid
+            proc = autoinc_col.type._cached_result_processor(
+                self.dialect, None
+            )
+        else:
+            proc = None
+
+        def get(lastrowid, parameters):
+            if proc is not None:
+                lastrowid = proc(lastrowid)
+
+            if lastrowid is None:
+                return tuple(getter(parameters) for getter, col in getters)
+            else:
+                return tuple(
+                    lastrowid if col is autoinc_col else getter(parameters)
+                    for getter, col in getters
+                )
+
+        return get
+
+    @util.memoized_property
+    def _inserted_primary_key_from_returning_getter(self):
+        key_getter = self._key_getters_for_crud_column[2]
+        table = self.statement.table
+
+        ret = {col: idx for idx, col in enumerate(self.returning)}
+
+        getters = [
+            (operator.itemgetter(ret[col]), True)
+            if col in ret
+            else (operator.methodcaller("get", key_getter(col), None), False)
+            for col in table.primary_key
+        ]
+
+        def get(row, parameters):
+            return tuple(
+                getter(row) if use_row else getter(parameters)
+                for getter, use_row in getters
+            )
+
+        return get
+
     def default_from(self):
         """Called when a SELECT statement has no froms, and no FROM clause is
         to be appended.