[pgpool-general: 8934] Server-side cursors using Declare/Describe do not work in pgpool-ii

[Heather Lapointe]

Hi,
I am on pgpool-ii 4.4.4 hoping that it would fix a particular Describe
issue I was seeing with psycopg3. (But alas,
https://git.postgresql.org/gitweb/?p=pgpool2.git;a=commit;h=0d54c68d5cfba549e5b6fb7d3247d66ee50ab1d9
did not fix my issue).

I was able to track down with the psycopg3 developers that the reason
for the failure is that we do not track portals for DECLARE and
subsequent calls to Describe could end up failing.

Here is the issue https://github.com/psycopg/psycopg/issues/648, but I
will post the relevant pgpool-ii log:
2023-09-25 17:44:57.534: [unknown] pid 157: LOG:  Parse message from frontend.
2023-09-25 17:44:57.534: [unknown] pid 157: DETAIL:  statement: "",
query: "BEGIN"
2023-09-25 17:44:57.535: [unknown] pid 157: LOG:  Bind message from frontend.
2023-09-25 17:44:57.535: [unknown] pid 157: DETAIL:  portal: "", statement: ""
2023-09-25 17:44:57.535: [unknown] pid 157: LOG:  Describe message
from frontend.
2023-09-25 17:44:57.535: [unknown] pid 157: DETAIL:  portal: ""
2023-09-25 17:44:57.535: [unknown] pid 157: LOG:  Execute message from frontend.
2023-09-25 17:44:57.535: [unknown] pid 157: DETAIL:  portal: ""
2023-09-25 17:44:57.535: [unknown] pid 157: LOG:  Sync message from frontend.
2023-09-25 17:44:57.734: [unknown] pid 157: LOG:  Parse message from frontend.
2023-09-25 17:44:57.735: [unknown] pid 157: DETAIL:  statement: "",
query: "DECLARE "serverside-cursor-broken" NO SCROLL CURSOR FOR SELECT
3"
2023-09-25 17:44:57.735: [unknown] pid 157: LOG:  Bind message from frontend.
2023-09-25 17:44:57.735: [unknown] pid 157: DETAIL:  portal: "", statement: ""
2023-09-25 17:44:57.735: [unknown] pid 157: LOG:  Describe message
from frontend.
2023-09-25 17:44:57.735: [unknown] pid 157: DETAIL:  portal: ""
2023-09-25 17:44:57.735: [unknown] pid 157: LOG:  Execute message from frontend.
2023-09-25 17:44:57.735: [unknown] pid 157: DETAIL:  portal: ""
2023-09-25 17:44:57.735: [unknown] pid 157: LOG:  Sync message from frontend.
2023-09-25 17:44:58.013: [unknown] pid 157: LOG:  Describe message
from frontend.
2023-09-25 17:44:58.013: [unknown] pid 157: DETAIL:  portal:
"serverside-cursor-broken"
2023-09-25 17:44:58.013: [unknown] pid 157: FATAL:  unable to execute Describe
2023-09-25 17:44:58.013: [unknown] pid 157: DETAIL:  unable to get the
bind message

I'd think that fixing this would either involve tracking DECLARE
statements like other portal statements, or passing the message to the
primary to let it handle the Describe on its own.

Let me know if there is anything I can do to help!
- Heather