After 10 -> 15 upgrade getting "cannot commit while a portal is pinned" on one python function - Mailing list pgsql-general

Greetings!

I built a trigger fired process that copies an "order" from our production database to our dev database.  An order, in this case, is an initial row from a table and all of the rows in all of the tables in that database/schema that are needed to satisfy all of the foreign key constraints for the original insert.  Through a web page, one of our folks can select a schema and an order id to copy.  That information is then inserted into a table.  A trigger attached to that table takes care of copying the necessary rows using a function that uses both plython3u and psycopg2.  I can supply the source code if that will help.

On postgresql 10 using plpython2, this function worked great.

After migration to 15 (now 15.5) and a switch to plpython3 (no code change needed inside the function) logging inside the function tells me that everything completes except the exit.

I then get this error:

NOTICE:  update cargotel_common.copy_orders_to_dev set copy_completed = 't', copy_completed_timestamp = clock_timestamp() where id = 21
ERROR:  cannot commit while a portal is pinned

What the heck?

I did find this error inside the source code.  This is from 15.6 source:

jross@workstation:~/postgresql-15.6$ grep -R -C20 "cannot commit while a portal is pinned" *
src/backend/utils/mmgr/portalmem.c- */
src/backend/utils/mmgr/portalmem.c-bool
src/backend/utils/mmgr/portalmem.c-PreCommit_Portals(bool isPrepare)
src/backend/utils/mmgr/portalmem.c-{
src/backend/utils/mmgr/portalmem.c-    bool        result = false;
src/backend/utils/mmgr/portalmem.c-    HASH_SEQ_STATUS status;
src/backend/utils/mmgr/portalmem.c-    PortalHashEnt *hentry;
src/backend/utils/mmgr/portalmem.c-
src/backend/utils/mmgr/portalmem.c-    hash_seq_init(&status, PortalHashTable);
src/backend/utils/mmgr/portalmem.c-
src/backend/utils/mmgr/portalmem.c-    while ((hentry = (PortalHashEnt *) hash_seq_search(&status)) != NULL)
src/backend/utils/mmgr/portalmem.c-    {
src/backend/utils/mmgr/portalmem.c-        Portal        portal = hentry->portal;
src/backend/utils/mmgr/portalmem.c-
src/backend/utils/mmgr/portalmem.c-        /*
src/backend/utils/mmgr/portalmem.c-         * There should be no pinned portals anymore. Complain if someone
src/backend/utils/mmgr/portalmem.c-         * leaked one. Auto-held portals are allowed; we assume that whoever
src/backend/utils/mmgr/portalmem.c-         * pinned them is managing them.
src/backend/utils/mmgr/portalmem.c-         */
src/backend/utils/mmgr/portalmem.c-        if (portal->portalPinned && !portal->autoHeld)
src/backend/utils/mmgr/portalmem.c:            elog(ERROR, "cannot commit while a portal is pinned");
src/backend/utils/mmgr/portalmem.c-
src/backend/utils/mmgr/portalmem.c-        /*
src/backend/utils/mmgr/portalmem.c-         * Do not touch active portals --- this can only happen in the case of
src/backend/utils/mmgr/portalmem.c-         * a multi-transaction utility command, such as VACUUM, or a commit in
src/backend/utils/mmgr/portalmem.c-         * a procedure.
src/backend/utils/mmgr/portalmem.c-         *
src/backend/utils/mmgr/portalmem.c-         * Note however that any resource owner attached to such a portal is
src/backend/utils/mmgr/portalmem.c-         * still going to go away, so don't leave a dangling pointer.  Also
src/backend/utils/mmgr/portalmem.c-         * unregister any snapshots held by the portal, mainly to avoid
src/backend/utils/mmgr/portalmem.c-         * snapshot leak warnings from ResourceOwnerRelease().
src/backend/utils/mmgr/portalmem.c-         */
src/backend/utils/mmgr/portalmem.c-        if (portal->status == PORTAL_ACTIVE)
src/backend/utils/mmgr/portalmem.c-        {
src/backend/utils/mmgr/portalmem.c-            if (portal->holdSnapshot)
src/backend/utils/mmgr/portalmem.c-            {
src/backend/utils/mmgr/portalmem.c-                if (portal->resowner)
src/backend/utils/mmgr/portalmem.c-                    UnregisterSnapshotFromOwner(portal->holdSnapshot,
src/backend/utils/mmgr/portalmem.c-                                                portal->resowner);
src/backend/utils/mmgr/portalmem.c-                portal->holdSnapshot = NULL;
src/backend/utils/mmgr/portalmem.c-            }

Do I have any idea of how to fix this after reading this bit of code?  No.

This error has been reported here before on December 2, 2022 and in other places as well.

https://www.postgresql.org/message-id/1061909348.200334.1669970706749%40mail.yahoo.com

No responses though to this message though.

In the code this:

src/backend/utils/mmgr/portalmem.c-        /*
src/backend/utils/mmgr/portalmem.c-         * There should be no pinned portals anymore. Complain if someone
src/backend/utils/mmgr/portalmem.c-         * leaked one. Auto-held portals are allowed; we assume that whoever
src/backend/utils/mmgr/portalmem.c-         * pinned them is managing them.
src/backend/utils/mmgr/portalmem.c-         */

makes me wonder if this error is specific to plpython3?

I can think of a way to maybe workaround this but this seems to be something that needs to be handled in a better way than slapping on a hacky bandaid.

Thanks for reading and for any suggestions, including clue-by-fours :-)

Jeff