As I was working through steps to make PL/Python more thread-safe, I
noticed that the initialization code of PL/Python is pretty messy. I
think some of this has grown while both Python 2 and 3 were supported,
because they required different initialization steps, and we had some
defenses against accidentally running both at the same time. But that
is over, and right now a lot of this doesn't make sense anymore. For
example, the function PLy_init_interp() said "Initialize the Python
interpreter ..." but it didn't actually do this, and PLy_init_plpy()
said "initialize plpy module" but it didn't do that either (or at least
they used the term "initialize" in non-standard ways).
Here are some patches to clean this up. After this change, all the
global initialization is called directly from _PG_init(), and the plpy
module initialization is all called from its registered initialization
function PyInit_plpy(). (For the thread-safety job, the plpy module
initialization will need to be rewritten using a different API. That's
why I'm keen to have it clearly separated.) I also tried to add more
comments and make existing comments more precise. There was also some
apparently obsolete or redundant code that could be deleted.
Surely, all of this will need some more rounds of careful scrutiny, but
I think the overall code arrangement is correct and an improvement.
From d07fa3f6d7f729ca457a4db1060ef934fa5ba2ef Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <[email protected]>
Date: Tue, 30 Dec 2025 22:17:57 +0100
Subject: [PATCH v1 1/4] plpython: Remove commented out code
This code has been commented out since the first commit of plpython.
It doesn't seem worth keeping.
---
src/pl/plpython/plpy_plpymodule.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/src/pl/plpython/plpy_plpymodule.c
b/src/pl/plpython/plpy_plpymodule.c
index 89931612c5b..66781291519 100644
--- a/src/pl/plpython/plpy_plpymodule.c
+++ b/src/pl/plpython/plpy_plpymodule.c
@@ -153,8 +153,6 @@ PLy_init_plpy(void)
PyModule_Create(&PLy_module);
- /* PyDict_SetItemString(plpy, "PlanType", (PyObject *) &PLy_PlanType);
*/
-
/*
* initialize main module, and add plpy
*/
base-commit: ffdcc9c638eeb71d2e6990e27f91623736603b58
--
2.52.0
From a174797efde3b5c0f7ead1fa2a89fde0358ceeed Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <[email protected]>
Date: Tue, 30 Dec 2025 22:17:57 +0100
Subject: [PATCH v1 2/4] plpython: Clean up PyModule_AddObject() uses
The comments "PyModule_AddObject does not add a refcount to the
object, for some odd reason" seem distracting. Arguably, this
behavior is expected, not odd. Also, the additional references
created by the existing code do no seem necessary. But we should
clean up the reference in the error case, as suggested by the Python
documentation.
---
src/pl/plpython/plpy_plpymodule.c | 39 ++++++++++++++-----------------
1 file changed, 18 insertions(+), 21 deletions(-)
diff --git a/src/pl/plpython/plpy_plpymodule.c
b/src/pl/plpython/plpy_plpymodule.c
index 66781291519..194739c3db6 100644
--- a/src/pl/plpython/plpy_plpymodule.c
+++ b/src/pl/plpython/plpy_plpymodule.c
@@ -172,18 +172,6 @@ PLy_add_exceptions(PyObject *plpy)
PyObject *excmod;
HASHCTL hash_ctl;
- excmod = PyModule_Create(&PLy_exc_module);
- if (excmod == NULL)
- PLy_elog(ERROR, "could not create the spiexceptions module");
-
- /*
- * PyModule_AddObject does not add a refcount to the object, for some
odd
- * reason; we must do that.
- */
- Py_INCREF(excmod);
- if (PyModule_AddObject(plpy, "spiexceptions", excmod) < 0)
- PLy_elog(ERROR, "could not add the spiexceptions module");
-
PLy_exc_error = PLy_create_exception("plpy.Error", NULL, NULL,
"Error", plpy);
PLy_exc_fatal = PLy_create_exception("plpy.Fatal", NULL, NULL,
@@ -191,12 +179,22 @@ PLy_add_exceptions(PyObject *plpy)
PLy_exc_spi_error = PLy_create_exception("plpy.SPIError", NULL, NULL,
"SPIError", plpy);
+ excmod = PyModule_Create(&PLy_exc_module);
+ if (excmod == NULL)
+ PLy_elog(ERROR, "could not create the spiexceptions module");
+
hash_ctl.keysize = sizeof(int);
hash_ctl.entrysize = sizeof(PLyExceptionEntry);
PLy_spi_exceptions = hash_create("PL/Python SPI exceptions", 256,
&hash_ctl, HASH_ELEM | HASH_BLOBS);
PLy_generate_spi_exceptions(excmod, PLy_exc_spi_error);
+
+ if (PyModule_AddObject(plpy, "spiexceptions", excmod) < 0)
+ {
+ Py_XDECREF(excmod);
+ PLy_elog(ERROR, "could not add the spiexceptions module");
+ }
}
/*
@@ -212,19 +210,18 @@ PLy_create_exception(char *name, PyObject *base, PyObject
*dict,
if (exc == NULL)
PLy_elog(ERROR, NULL);
- /*
- * PyModule_AddObject does not add a refcount to the object, for some
odd
- * reason; we must do that.
- */
- Py_INCREF(exc);
- PyModule_AddObject(mod, modname, exc);
-
/*
* The caller will also store a pointer to the exception object in some
- * permanent variable, so add another ref to account for that. This is
- * probably excessively paranoid, but let's be sure.
+ * permanent variable, so add another ref to account for that.
*/
Py_INCREF(exc);
+
+ if (PyModule_AddObject(mod, modname, exc) < 0)
+ {
+ Py_XDECREF(exc);
+ PLy_elog(ERROR, "could not add exceptions %s", name);
+ }
+
return exc;
}
--
2.52.0
From a9d8b839306be227a1adce0c4c3605fc3114736b Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <[email protected]>
Date: Tue, 30 Dec 2025 22:17:57 +0100
Subject: [PATCH v1 3/4] plpython: Remove duplicate PyModule_Create()
This seems to have existed like this since Python 3 support was
added (commit dd4cd55c158), but it's unclear what this second call is
supposed to accomplish.
---
src/pl/plpython/plpy_plpymodule.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/src/pl/plpython/plpy_plpymodule.c
b/src/pl/plpython/plpy_plpymodule.c
index 194739c3db6..2d76c6a5573 100644
--- a/src/pl/plpython/plpy_plpymodule.c
+++ b/src/pl/plpython/plpy_plpymodule.c
@@ -151,8 +151,6 @@ PLy_init_plpy(void)
PLy_subtransaction_init_type();
PLy_cursor_init_type();
- PyModule_Create(&PLy_module);
-
/*
* initialize main module, and add plpy
*/
--
2.52.0
From 247ea7aa96df56253754e88c17974488ea09e39b Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <[email protected]>
Date: Tue, 30 Dec 2025 22:17:57 +0100
Subject: [PATCH v1 4/4] plpython: Streamline initialization
The initialization of PL/Python (the Python interpreter, the global
state, the plpy module) was arranged confusingly across different
functions with unclear and confusing boundaries. For example,
PLy_init_interp() said "Initialize the Python interpreter ..." but it
didn't actually do this, and PLy_init_plpy() said "initialize plpy
module" but it didn't do that either. After this change, all the
global initialization is called directly from _PG_init(), and the plpy
module initialization is all called from its registered initialization
function PyInit_plpy().
---
src/pl/plpython/plpy_main.c | 77 ++++++++++++++++---------------
src/pl/plpython/plpy_plpymodule.c | 25 +---------
src/pl/plpython/plpy_plpymodule.h | 1 -
3 files changed, 40 insertions(+), 63 deletions(-)
diff --git a/src/pl/plpython/plpy_main.c b/src/pl/plpython/plpy_main.c
index 7673b5eca7b..482ca7a1ada 100644
--- a/src/pl/plpython/plpy_main.c
+++ b/src/pl/plpython/plpy_main.c
@@ -39,11 +39,9 @@ PG_FUNCTION_INFO_V1(plpython3_call_handler);
PG_FUNCTION_INFO_V1(plpython3_inline_handler);
-static void PLy_initialize(void);
static PLyTrigType PLy_procedure_is_trigger(Form_pg_proc procStruct);
static void plpython_error_callback(void *arg);
static void plpython_inline_error_callback(void *arg);
-static void PLy_init_interp(void);
static PLyExecutionContext *PLy_push_execution_context(bool atomic_context);
static void PLy_pop_execution_context(void);
@@ -58,25 +56,52 @@ static PLyExecutionContext *PLy_execution_contexts = NULL;
void
_PG_init(void)
{
- pg_bindtextdomain(TEXTDOMAIN);
+ PyObject *main_mod;
+ PyObject *main_dict;
+ PyObject *GD;
+ PyObject *plpy_mod;
- PLy_initialize();
-}
+ pg_bindtextdomain(TEXTDOMAIN);
-/*
- * Perform one-time setup of PL/Python.
- */
-static void
-PLy_initialize(void)
-{
+ /* Add plpy to table of built-in modules. */
PyImport_AppendInittab("plpy", PyInit_plpy);
+
+ /* Initialize Python interpreter. */
Py_Initialize();
- PyImport_ImportModule("plpy");
- PLy_init_interp();
- PLy_init_plpy();
+
+ main_mod = PyImport_AddModule("__main__");
+ if (main_mod == NULL || PyErr_Occurred())
+ PLy_elog(ERROR, "could not get \"__main__\" module");
+ Py_INCREF(main_mod);
+
+ main_dict = PyModule_GetDict(main_mod);
+
+ /*
+ * Set up GD.
+ */
+ GD = PyDict_New();
+ if (GD == NULL)
+ PLy_elog(ERROR, NULL);
+ PyDict_SetItemString(main_dict, "GD", GD);
+
+ /*
+ * Import plpy.
+ */
+ plpy_mod = PyImport_ImportModule("plpy");
+ if (plpy_mod == NULL)
+ PLy_elog(ERROR, "could not import \"plpy\" module");
+ PyDict_SetItemString(main_dict, "plpy", plpy_mod);
+ if (PyErr_Occurred())
+ PLy_elog(ERROR, "could not import \"plpy\" module");
+
+ Py_DECREF(main_mod);
+
if (PyErr_Occurred())
PLy_elog(FATAL, "untrapped error in initialization");
+ Py_INCREF(main_dict);
+ PLy_interp_globals = main_dict;
+
init_procedure_caches();
explicit_subtransactions = NIL;
@@ -84,30 +109,6 @@ PLy_initialize(void)
PLy_execution_contexts = NULL;
}
-/*
- * This should be called only once, from PLy_initialize. Initialize the Python
- * interpreter and global data.
- */
-static void
-PLy_init_interp(void)
-{
- static PyObject *PLy_interp_safe_globals = NULL;
- PyObject *mainmod;
-
- mainmod = PyImport_AddModule("__main__");
- if (mainmod == NULL || PyErr_Occurred())
- PLy_elog(ERROR, "could not import \"__main__\" module");
- Py_INCREF(mainmod);
- PLy_interp_globals = PyModule_GetDict(mainmod);
- PLy_interp_safe_globals = PyDict_New();
- if (PLy_interp_safe_globals == NULL)
- PLy_elog(ERROR, NULL);
- PyDict_SetItemString(PLy_interp_globals, "GD", PLy_interp_safe_globals);
- Py_DECREF(mainmod);
- if (PLy_interp_globals == NULL || PyErr_Occurred())
- PLy_elog(ERROR, "could not initialize globals");
-}
-
Datum
plpython3_validator(PG_FUNCTION_ARGS)
{
diff --git a/src/pl/plpython/plpy_plpymodule.c
b/src/pl/plpython/plpy_plpymodule.c
index 2d76c6a5573..e24ad02e086 100644
--- a/src/pl/plpython/plpy_plpymodule.c
+++ b/src/pl/plpython/plpy_plpymodule.c
@@ -133,35 +133,12 @@ PyInit_plpy(void)
PLy_add_exceptions(m);
- return m;
-}
-
-void
-PLy_init_plpy(void)
-{
- PyObject *main_mod,
- *main_dict,
- *plpy_mod;
-
- /*
- * initialize plpy module
- */
PLy_plan_init_type();
PLy_result_init_type();
PLy_subtransaction_init_type();
PLy_cursor_init_type();
- /*
- * initialize main module, and add plpy
- */
- main_mod = PyImport_AddModule("__main__");
- main_dict = PyModule_GetDict(main_mod);
- plpy_mod = PyImport_AddModule("plpy");
- if (plpy_mod == NULL)
- PLy_elog(ERROR, "could not import \"plpy\" module");
- PyDict_SetItemString(main_dict, "plpy", plpy_mod);
- if (PyErr_Occurred())
- PLy_elog(ERROR, "could not import \"plpy\" module");
+ return m;
}
static void
diff --git a/src/pl/plpython/plpy_plpymodule.h
b/src/pl/plpython/plpy_plpymodule.h
index 1ca3823daf2..88f902346a6 100644
--- a/src/pl/plpython/plpy_plpymodule.h
+++ b/src/pl/plpython/plpy_plpymodule.h
@@ -13,6 +13,5 @@ extern HTAB *PLy_spi_exceptions;
PyMODINIT_FUNC PyInit_plpy(void);
-extern void PLy_init_plpy(void);
#endif /* PLPY_PLPYMODULE_H */
--
2.52.0
