Backport patch to preserve SQLSTATE in PL/python.

We had backported PL/python from PostgreSQL 9.1, but not this patch
that was applied later to the stable branch. I noticed when I started
looking at this, while cleaning up the source file/line number information
in error messages.

I did not backport the regression test changes, because we had apparently
not backported other regression test changes either, and I was not able
to make the tests work easily.

Original commit:

commit d2192a108c7b118d430f03cff0ff84861d5026e0
Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date:   Thu Nov 24 17:18:43 2011 +0200

    Preserve SQLSTATE when an SPI error is propagated through PL/python
    exception handler. This was a regression in 9.1, when the capability
    to catch specific SPI errors was added, so backpatch to 9.1.

    Mika Eloranta, with some editing by Jan Urbański.

src/pl/plpython/expected/plpython_error.out

@@ -2,7 +2,7 @@
 -- the trigger handler once. the errors and subsequent core dump were
 -- interesting.
 SELECT invalid_type_uncaught('rick');
-ERROR:  plpy.SPIError: type "test" does not exist (plpython.c:4703)
+ERROR:  plpy.SPIError: type "test" does not exist
 CONTEXT:  Traceback (most recent call last):
   PL/Python function "invalid_type_uncaught", line 3, in <module>
     SD["plan"] = plpy.prepare(q, [ "test" ])
@@ -16,7 +16,7 @@ CONTEXT:  PL/Python function "invalid_type_caught"
 (1 row)
 
 SELECT invalid_type_reraised('rick');
-ERROR:  plpy.Error: type "test" does not exist (plpython.c:4703)
+ERROR:  plpy.Error: type "test" does not exist
 CONTEXT:  Traceback (most recent call last):
   PL/Python function "invalid_type_reraised", line 6, in <module>
     plpy.error(str(ex))

src/pl/plpython/expected/plpython_subtransaction.out

@@ -46,7 +46,7 @@ SELECT * FROM subtransaction_tbl order by i;
 
 TRUNCATE subtransaction_tbl;
 SELECT subtransaction_test('SPI');
-ERROR:  plpy.SPIError: invalid input syntax for integer: "oops" (plpython.c:4718)
+ERROR:  plpy.SPIError: invalid input syntax for integer: "oops"
 LINE 1: INSERT INTO subtransaction_tbl VALUES ('oops')
                                                ^
 QUERY:  INSERT INTO subtransaction_tbl VALUES ('oops')
@@ -98,7 +98,7 @@ SELECT * FROM subtransaction_tbl order by i;
 
 TRUNCATE subtransaction_tbl;
 SELECT subtransaction_ctx_test('SPI');
-ERROR:  plpy.SPIError: invalid input syntax for integer: "oops" (plpython.c:4718)
+ERROR:  plpy.SPIError: invalid input syntax for integer: "oops"
 LINE 1: INSERT INTO subtransaction_tbl VALUES ('oops')
                                                ^
 QUERY:  INSERT INTO subtransaction_tbl VALUES ('oops')

src/pl/plpython/plpython.c

@@ -346,7 +346,7 @@ static char *PLy_procedure_name(PLyProcedure *);
 static void
 PLy_elog(int, const char *,...)
 __attribute__((format(printf, 2, 3)));
-static void PLy_get_spi_error_data(PyObject *exc, char **detail, char **hint, char **query, int *position);
+static void PLy_get_spi_error_data(PyObject *exc, int *sqlerrcode, char **detail, char **hint, char **query, int *position);
 static void PLy_traceback(char **, char **, int *);
 
 static void *PLy_malloc(size_t);
@@ -4638,7 +4638,7 @@ PLy_spi_exception_set(PyObject *excclass, ErrorData *edata)
 	if (!spierror)
 		goto failure;
 
-	spidata = Py_BuildValue("(zzzi)", edata->detail, edata->hint,
+	spidata = Py_BuildValue("(izzzi)", edata->sqlerrcode, edata->detail, edata->hint,
 							edata->internalquery, edata->internalpos);
 	if (!spidata)
 		goto failure;
@@ -4678,6 +4678,7 @@ PLy_elog(int elevel, const char *fmt,...)
 			   *val,
 			   *tb;
 	const char *primary = NULL;
+	int        sqlerrcode = 0;
 	char	   *detail = NULL;
 	char	   *hint = NULL;
 	char	   *query = NULL;
@@ -4687,7 +4688,7 @@ PLy_elog(int elevel, const char *fmt,...)
 	if (exc != NULL)
 	{
 		if (PyErr_GivenExceptionMatches(val, PLy_exc_spi_error))
-			PLy_get_spi_error_data(val, &detail, &hint, &query, &position);
+			PLy_get_spi_error_data(val, &sqlerrcode, &detail, &hint, &query, &position);
 		else if (PyErr_GivenExceptionMatches(val, PLy_exc_fatal))
 			elevel = FATAL;
 	}
@@ -4728,7 +4729,8 @@ PLy_elog(int elevel, const char *fmt,...)
 	PG_TRY();
 	{
 		ereport(elevel,
-				(errmsg("%s", primary ? primary : "no exception data"),
+				(errcode(sqlerrcode ? sqlerrcode : ERRCODE_INTERNAL_ERROR),
+				 errmsg("%s", primary ? primary : "no exception data"),
 				 (detail) ? errdetail("%s", detail) : 0,
 				 (tb_depth > 0 && tbmsg) ? errcontext("%s", tbmsg) : 0,
 				 (hint) ? errhint("%s", hint) : 0,
@@ -4759,7 +4761,7 @@ PLy_elog(int elevel, const char *fmt,...)
  * Extract the error data from a SPIError
  */
 static void
-PLy_get_spi_error_data(PyObject *exc, char **detail, char **hint, char **query, int *position)
+PLy_get_spi_error_data(PyObject *exc, int* sqlerrcode, char **detail, char **hint, char **query, int *position)
 {
 	PyObject   *spidata = NULL;
 
@@ -4767,7 +4769,7 @@ PLy_get_spi_error_data(PyObject *exc, char **detail, char **hint, char **query,
 	if (!spidata)
 		goto cleanup;
 
-	if (!PyArg_ParseTuple(spidata, "zzzi", detail, hint, query, position))
+	if (!PyArg_ParseTuple(spidata, "izzzi", sqlerrcode, detail, hint, query, position))
 		goto cleanup;
 
 cleanup: