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Issue 5670: special-case pickling of dicts. This nearly doubles the performance of dict pickling in cPickle.

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This commit is contained in:
Collin Winter 2009-05-25 04:34:39 +00:00
parent 87e5006d8c
commit 179bf213ea
1 changed files with 78 additions and 9 deletions
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87
Modules/cPickle.c
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@ -1860,13 +1860,74 @@ BatchFailed:
return -1;
}
/* This is a variant of batch_dict() above that specializes for dicts, with no
* support for dict subclasses. Like batch_dict(), we batch up chunks of
* MARK key value ... key value SETITEMS
* opcode sequences. Calling code should have arranged to first create an
* empty dict, or dict-like object, for the SETITEMS to operate on.
* Returns 0 on success, -1 on error.
*
* Note that this currently doesn't work for protocol 0.
*/
static int
batch_dict_exact(Picklerobject *self, PyObject *obj)
{
PyObject *key = NULL, *value = NULL;
int i;
Py_ssize_t dict_size, ppos = 0;
static char setitem = SETITEM;
static char setitems = SETITEMS;
assert(obj != NULL);
assert(self->proto > 0);
dict_size = PyDict_Size(obj);
/* Special-case len(d) == 1 to save space. */
if (dict_size == 1) {
PyDict_Next(obj, &ppos, &key, &value);
if (save(self, key, 0) < 0)
return -1;
if (save(self, value, 0) < 0)
return -1;
if (self->write_func(self, &setitem, 1) < 0)
return -1;
return 0;
}
/* Write in batches of BATCHSIZE. */
do {
i = 0;
if (self->write_func(self, &MARKv, 1) < 0)
return -1;
while (PyDict_Next(obj, &ppos, &key, &value)) {
if (save(self, key, 0) < 0)
return -1;
if (save(self, value, 0) < 0)
return -1;
if (++i == BATCHSIZE)
break;
}
if (self->write_func(self, &setitems, 1) < 0)
return -1;
if (PyDict_Size(obj) != dict_size) {
PyErr_Format(
PyExc_RuntimeError,
"dictionary changed size during iteration");
return -1;
}
} while (i == BATCHSIZE);
return 0;
}
static int
save_dict(Picklerobject *self, PyObject *args)
{
int res = -1;
char s[3];
int len;
PyObject *iter;
if (self->fast && !fast_save_enter(self, args))
goto finally;
@ -1898,15 +1959,23 @@ save_dict(Picklerobject *self, PyObject *args)
goto finally;
/* Materialize the dict items. */
iter = PyObject_CallMethod(args, "iteritems", "()");
if (iter == NULL)
goto finally;
if (Py_EnterRecursiveCall(" while pickling an object") == 0)
{
res = batch_dict(self, iter);
Py_LeaveRecursiveCall();
if (PyDict_CheckExact(args) && self->proto > 0) {
/* We can take certain shortcuts if we know this is a dict and
not a dict subclass. */
if (Py_EnterRecursiveCall(" while pickling an object") == 0) {
res = batch_dict_exact(self, args);
Py_LeaveRecursiveCall();
}
} else {
PyObject *iter = PyObject_CallMethod(args, "iteritems", "()");
if (iter == NULL)
goto finally;
if (Py_EnterRecursiveCall(" while pickling an object") == 0) {
res = batch_dict(self, iter);
Py_LeaveRecursiveCall();
}
Py_DECREF(iter);
}
Py_DECREF(iter);
finally:
if (self->fast && !fast_save_leave(self, args))