This patch needs another close pass and possibly some refactoring to
avoid copy-and-paste, but I'm putting this out here, since people are
already testing with Python 3.11 and will surely run into this problem.
The way plpy.commit() and plpy.rollback() handle errors is not ideal.
They end up just longjmping back to the main loop, without telling the
Python interpreter about it. This hasn't been a problem so far,
apparently, but with Python 3.11-to-be, this appears to cause corruption
in the state of the Python interpreter. This is readily reproducible
and will cause crashes in the plpython_transaction test.
The fix is that we need to catch the PostgreSQL error and turn it into a
Python exception, like we do for other places where plpy.* methods call
into PostgreSQL internals.From 31bbd62f43ceb0542e0a311dc28704fd702caeb3 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <pe...@eisentraut.org>
Date: Wed, 22 Dec 2021 09:01:24 +0100
Subject: [PATCH v1] Set Python exception after failed commit or rollback
When plpy.commit() or plpy.rollback() failed, the SPI code would
ereport(ERROR) and jump all the way back to the main loop, bypassing
PL/Python. By contrast, in plpy.execute(), we catch the ereport() and
generate a Python exception. This has the advantage that you can
catch the exception and you get better backtraces.
An additional problem is apparently that beginning in Python
3.11-to-be, longjmping out of the Python interpreter leaves its
internal state inconsistent, and subsequent invocations of PL/Python
code will crash. With previous Python versions, this has apparently
not been a problem.
To fix, adapt the logic in PLy_spi_subtransaction_abort() (which is
used by plpy.execute() and others) to catch the PostgreSQL error and
turn it into a Python exception. Move some code around to avoid
additional cross-file zigzag from this.
---
.../expected/plpython_transaction.out | 18 ++-
src/pl/plpython/plpy_plpymodule.c | 30 -----
src/pl/plpython/plpy_spi.c | 106 ++++++++++++++++++
src/pl/plpython/plpy_spi.h | 3 +
4 files changed, 121 insertions(+), 36 deletions(-)
diff --git a/src/pl/plpython/expected/plpython_transaction.out
b/src/pl/plpython/expected/plpython_transaction.out
index 14152993c7..9fd9ef500e 100644
--- a/src/pl/plpython/expected/plpython_transaction.out
+++ b/src/pl/plpython/expected/plpython_transaction.out
@@ -55,8 +55,11 @@ for i in range(0, 10):
return 1
$$;
SELECT transaction_test2();
-ERROR: invalid transaction termination
-CONTEXT: PL/Python function "transaction_test2"
+ERROR: spiexceptions.InvalidTransactionTermination: invalid transaction
termination
+CONTEXT: Traceback (most recent call last):
+ PL/Python function "transaction_test2", line 5, in <module>
+ plpy.commit()
+PL/Python function "transaction_test2"
SELECT * FROM test1;
a | b
---+---
@@ -70,7 +73,7 @@ plpy.execute("CALL transaction_test1()")
return 1
$$;
SELECT transaction_test3();
-ERROR: spiexceptions.InvalidTransactionTermination: invalid transaction
termination
+ERROR: spiexceptions.InvalidTransactionTermination:
spiexceptions.InvalidTransactionTermination: invalid transaction termination
CONTEXT: Traceback (most recent call last):
PL/Python function "transaction_test3", line 2, in <module>
plpy.execute("CALL transaction_test1()")
@@ -88,7 +91,7 @@ plpy.execute("DO LANGUAGE plpythonu $x$ plpy.commit() $x$")
return 1
$$;
SELECT transaction_test4();
-ERROR: spiexceptions.InvalidTransactionTermination: invalid transaction
termination
+ERROR: spiexceptions.InvalidTransactionTermination:
spiexceptions.InvalidTransactionTermination: invalid transaction termination
CONTEXT: Traceback (most recent call last):
PL/Python function "transaction_test4", line 2, in <module>
plpy.execute("DO LANGUAGE plpythonu $x$ plpy.commit() $x$")
@@ -100,8 +103,11 @@ s.enter()
plpy.commit()
$$;
WARNING: forcibly aborting a subtransaction that has not been exited
-ERROR: cannot commit while a subtransaction is active
-CONTEXT: PL/Python anonymous code block
+ERROR: spiexceptions.InvalidTransactionTermination: cannot commit while a
subtransaction is active
+CONTEXT: Traceback (most recent call last):
+ PL/Python anonymous code block, line 4, in <module>
+ plpy.commit()
+PL/Python anonymous code block
-- commit inside cursor loop
CREATE TABLE test2 (x int);
INSERT INTO test2 VALUES (0), (1), (2), (3), (4);
diff --git a/src/pl/plpython/plpy_plpymodule.c
b/src/pl/plpython/plpy_plpymodule.c
index 0365acc95b..907f89d153 100644
--- a/src/pl/plpython/plpy_plpymodule.c
+++ b/src/pl/plpython/plpy_plpymodule.c
@@ -40,8 +40,6 @@ static PyObject *PLy_fatal(PyObject *self, PyObject *args,
PyObject *kw);
static PyObject *PLy_quote_literal(PyObject *self, PyObject *args);
static PyObject *PLy_quote_nullable(PyObject *self, PyObject *args);
static PyObject *PLy_quote_ident(PyObject *self, PyObject *args);
-static PyObject *PLy_commit(PyObject *self, PyObject *args);
-static PyObject *PLy_rollback(PyObject *self, PyObject *args);
/* A list of all known exceptions, generated from backend/utils/errcodes.txt */
@@ -577,31 +575,3 @@ PLy_output(volatile int level, PyObject *self, PyObject
*args, PyObject *kw)
*/
Py_RETURN_NONE;
}
-
-static PyObject *
-PLy_commit(PyObject *self, PyObject *args)
-{
- PLyExecutionContext *exec_ctx = PLy_current_execution_context();
-
- SPI_commit();
- SPI_start_transaction();
-
- /* was cleared at transaction end, reset pointer */
- exec_ctx->scratch_ctx = NULL;
-
- Py_RETURN_NONE;
-}
-
-static PyObject *
-PLy_rollback(PyObject *self, PyObject *args)
-{
- PLyExecutionContext *exec_ctx = PLy_current_execution_context();
-
- SPI_rollback();
- SPI_start_transaction();
-
- /* was cleared at transaction end, reset pointer */
- exec_ctx->scratch_ctx = NULL;
-
- Py_RETURN_NONE;
-}
diff --git a/src/pl/plpython/plpy_spi.c b/src/pl/plpython/plpy_spi.c
index 99c1b4f28f..469a9b14ac 100644
--- a/src/pl/plpython/plpy_spi.c
+++ b/src/pl/plpython/plpy_spi.c
@@ -456,6 +456,112 @@ PLy_spi_execute_fetch_result(SPITupleTable *tuptable,
uint64 rows, int status)
return (PyObject *) result;
}
+PyObject *
+PLy_commit(PyObject *self, PyObject *args)
+{
+ volatile MemoryContext oldcontext;
+ volatile ResourceOwner oldowner;
+
+ oldcontext = CurrentMemoryContext;
+ oldowner = CurrentResourceOwner;
+
+ PG_TRY();
+ {
+ PLyExecutionContext *exec_ctx = PLy_current_execution_context();
+
+ SPI_commit();
+ SPI_start_transaction();
+
+ /* was cleared at transaction end, reset pointer */
+ exec_ctx->scratch_ctx = NULL;
+ }
+ PG_CATCH();
+ {
+ ErrorData *edata;
+ PLyExceptionEntry *entry;
+ PyObject *exc;
+
+ /* Save error info */
+ MemoryContextSwitchTo(oldcontext);
+ edata = CopyErrorData();
+ FlushErrorState();
+
+ MemoryContextSwitchTo(oldcontext);
+ CurrentResourceOwner = oldowner;
+
+ /* Look up the correct exception */
+ entry = hash_search(PLy_spi_exceptions, &(edata->sqlerrcode),
+ HASH_FIND, NULL);
+
+ /*
+ * This could be a custom error code, if that's the case
fallback to
+ * SPIError
+ */
+ exc = entry ? entry->exc : PLy_exc_spi_error;
+ /* Make Python raise the exception */
+ PLy_spi_exception_set(exc, edata);
+ FreeErrorData(edata);
+
+ return NULL;
+ }
+ PG_END_TRY();
+
+ Py_RETURN_NONE;
+}
+
+PyObject *
+PLy_rollback(PyObject *self, PyObject *args)
+{
+ volatile MemoryContext oldcontext;
+ volatile ResourceOwner oldowner;
+
+ oldcontext = CurrentMemoryContext;
+ oldowner = CurrentResourceOwner;
+
+ PG_TRY();
+ {
+ PLyExecutionContext *exec_ctx = PLy_current_execution_context();
+
+ SPI_rollback();
+ SPI_start_transaction();
+
+ /* was cleared at transaction end, reset pointer */
+ exec_ctx->scratch_ctx = NULL;
+ }
+ PG_CATCH();
+ {
+ ErrorData *edata;
+ PLyExceptionEntry *entry;
+ PyObject *exc;
+
+ /* Save error info */
+ MemoryContextSwitchTo(oldcontext);
+ edata = CopyErrorData();
+ FlushErrorState();
+
+ MemoryContextSwitchTo(oldcontext);
+ CurrentResourceOwner = oldowner;
+
+ /* Look up the correct exception */
+ entry = hash_search(PLy_spi_exceptions, &(edata->sqlerrcode),
+ HASH_FIND, NULL);
+
+ /*
+ * This could be a custom error code, if that's the case
fallback to
+ * SPIError
+ */
+ exc = entry ? entry->exc : PLy_exc_spi_error;
+ /* Make Python raise the exception */
+ PLy_spi_exception_set(exc, edata);
+ FreeErrorData(edata);
+
+ return NULL;
+ }
+ PG_END_TRY();
+
+ Py_RETURN_NONE;
+}
+
/*
* Utilities for running SPI functions in subtransactions.
*
diff --git a/src/pl/plpython/plpy_spi.h b/src/pl/plpython/plpy_spi.h
index a5e2e60da7..98ccd21093 100644
--- a/src/pl/plpython/plpy_spi.h
+++ b/src/pl/plpython/plpy_spi.h
@@ -12,6 +12,9 @@ extern PyObject *PLy_spi_prepare(PyObject *self, PyObject
*args);
extern PyObject *PLy_spi_execute(PyObject *self, PyObject *args);
extern PyObject *PLy_spi_execute_plan(PyObject *ob, PyObject *list, long
limit);
+extern PyObject *PLy_commit(PyObject *self, PyObject *args);
+extern PyObject *PLy_rollback(PyObject *self, PyObject *args);
+
typedef struct PLyExceptionEntry
{
int sqlstate; /* hash key, must be
first */
--
2.34.1
