Function PLy_subtransaction_enter

src/pl/plpython/plpy_subxactobject.c:86–126

* subxact.__enter__() or subxact.enter() * * Start an explicit subtransaction. SPI calls within an explicit * subtransaction will not start another one, so you can atomically * execute many SPI calls and still get a controllable exception if * one of them fails. */

 * one of them fails.
 */
static PyObject *
PLy_subtransaction_enter(PyObject *self, PyObject *unused)
{
	PLySubtransactionData *subxactdata;
	MemoryContext oldcontext;
	PLySubtransactionObject *subxact = (PLySubtransactionObject *) self;

	if (subxact->started)
	{
		PLy_exception_set(PyExc_ValueError, "this subtransaction has already been entered");
		return NULL;
	}

	if (subxact->exited)
	{
		PLy_exception_set(PyExc_ValueError, "this subtransaction has already been exited");
		return NULL;
	}

	subxact->started = true;
	oldcontext = CurrentMemoryContext;

	subxactdata = (PLySubtransactionData *)
		MemoryContextAlloc(TopTransactionContext,
						   sizeof(PLySubtransactionData));

	subxactdata->oldcontext = oldcontext;
	subxactdata->oldowner = CurrentResourceOwner;

	BeginInternalSubTransaction(NULL);

	/* Be sure that cells of explicit_subtransactions list are long-lived */
	MemoryContextSwitchTo(TopTransactionContext);
	explicit_subtransactions = lcons(subxactdata, explicit_subtransactions);

	/* Caller wants to stay in original memory context */
	MemoryContextSwitchTo(oldcontext);

	Py_INCREF(self);
	return self;
}

/*
 * subxact.__exit__(exc_type, exc, tb) or subxact.exit(exc_type, exc, tb)