Add check interrupts function.

Previously, if a python function took a long time, there was no way to
interrupt it.
The check_interrupts function now exposes the CHECK_INTERRUPTS PostgreSQL macro
to trap signals.

python/multicorn/utils.py

@@ -1,6 +1,7 @@
 from logging import ERROR, INFO, DEBUG, WARNING, CRITICAL
 try:
     from ._utils import _log_to_postgres
+    from ._utils import check_interrupts
 except ImportError as e:
     from warnings import warn
     warn("Not executed in a postgresql server,"
@@ -24,3 +25,4 @@ def log_to_postgres(message, level=INFO, hint=None, detail=None):
     if code is None:
         raise KeyError("Not a valid log level")
     _log_to_postgres(message, code, hint=hint, detail=detail)
+

src/utils.c

@@ -15,6 +15,7 @@
 #include <Python.h>
 #include "postgres.h"
 #include "multicorn.h"
+#include "miscadmin.h"
 
 
 struct module_state
@@ -114,8 +115,18 @@ log_to_postgres(PyObject *self, PyObject *args, PyObject *kwargs)
 	return Py_None;
 }
 
+static PyObject *
+py_check_interrupts(PyObject *self, PyObject *args, PyObject *kwargs)
+{
+	CHECK_FOR_INTERRUPTS();
+	Py_INCREF(Py_None);
+	return Py_None;
+}
+
+
 static PyMethodDef UtilsMethods[] = {
 	{"_log_to_postgres", (PyCFunction) log_to_postgres, METH_VARARGS | METH_KEYWORDS, "Log to postresql client"},
+	{"check_interrupts", (PyCFunction) py_check_interrupts, METH_VARARGS | METH_KEYWORDS, "Gives control back to PostgreSQL"},
 	{NULL, NULL, 0, NULL}
 };