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/*
* the PLySubtransaction class
*
* src/pl/plpython/plpy_subxactobject.c
*/
#include "postgres.h"
#include "access/xact.h"
#include "plpy_elog.h"
#include "plpy_subxactobject.h"
#include "plpython.h"
#include "utils/memutils.h"
List *explicit_subtransactions = NIL;
static void PLy_subtransaction_dealloc(PyObject *subxact);
static PyObject *PLy_subtransaction_enter(PyObject *self, PyObject *unused);
static PyObject *PLy_subtransaction_exit(PyObject *self, PyObject *args);
static char PLy_subtransaction_doc[] =
"PostgreSQL subtransaction context manager";
static PyMethodDef PLy_subtransaction_methods[] = {
{"__enter__", PLy_subtransaction_enter, METH_VARARGS, NULL},
{"__exit__", PLy_subtransaction_exit, METH_VARARGS, NULL},
/* user-friendly names for Python <2.6 */
{"enter", PLy_subtransaction_enter, METH_VARARGS, NULL},
{"exit", PLy_subtransaction_exit, METH_VARARGS, NULL},
{NULL, NULL, 0, NULL}
};
static PyTypeObject PLy_SubtransactionType = {
PyVarObject_HEAD_INIT(NULL, 0)
.tp_name = "PLySubtransaction",
.tp_basicsize = sizeof(PLySubtransactionObject),
.tp_dealloc = PLy_subtransaction_dealloc,
.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
.tp_doc = PLy_subtransaction_doc,
.tp_methods = PLy_subtransaction_methods,
};
void
PLy_subtransaction_init_type(void)
{
if (PyType_Ready(&PLy_SubtransactionType) < 0)
elog(ERROR, "could not initialize PLy_SubtransactionType");
}
/* s = plpy.subtransaction() */
PyObject *
PLy_subtransaction_new(PyObject *self, PyObject *unused)
{
PLySubtransactionObject *ob;
ob = PyObject_New(PLySubtransactionObject, &PLy_SubtransactionType);
if (ob == NULL)
return NULL;
ob->started = false;
ob->exited = false;
return (PyObject *) ob;
}
/* Python requires a dealloc function to be defined */
static void
PLy_subtransaction_dealloc(PyObject *subxact)
{
}
/*
* 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.
*/
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)
*
* Exit an explicit subtransaction. exc_type is an exception type, exc
* is the exception object, tb is the traceback. If exc_type is None,
* commit the subtransaction, if not abort it.
*
* The method signature is chosen to allow subtransaction objects to
* be used as context managers as described in
* <http://www.python.org/dev/peps/pep-0343/>.
*/
static PyObject *
PLy_subtransaction_exit(PyObject *self, PyObject *args)
{
PyObject *type;
PyObject *value;
PyObject *traceback;
PLySubtransactionData *subxactdata;
PLySubtransactionObject *subxact = (PLySubtransactionObject *) self;
if (!PyArg_ParseTuple(args, "OOO", &type, &value, &traceback))
return NULL;
if (!subxact->started)
{
PLy_exception_set(PyExc_ValueError, "this subtransaction has not been entered");
return NULL;
}
if (subxact->exited)
{
PLy_exception_set(PyExc_ValueError, "this subtransaction has already been exited");
return NULL;
}
if (explicit_subtransactions == NIL)
{
PLy_exception_set(PyExc_ValueError, "there is no subtransaction to exit from");
return NULL;
}
subxact->exited = true;
if (type != Py_None)
{
/* Abort the inner transaction */
RollbackAndReleaseCurrentSubTransaction();
}
else
{
ReleaseCurrentSubTransaction();
}
subxactdata = (PLySubtransactionData *) linitial(explicit_subtransactions);
explicit_subtransactions = list_delete_first(explicit_subtransactions);
MemoryContextSwitchTo(subxactdata->oldcontext);
CurrentResourceOwner = subxactdata->oldowner;
pfree(subxactdata);
Py_RETURN_NONE;
}
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