After giving it some thoughts, I see three possible solutions:
0. Do nothing about it. I would prefer the prepare is cleaned up.
1. assign a special name, eg "_psql_gdesc_", so that DEALLOCATE "_psql_gdesc_" can be issued afterwards.
[...]
The doc says about unnamed prepared statements - any new unnamed prepared statement deallocates previous by self. From psql environment is not possible to create unnamed prepared statement.
That is a good point. It seems that it is not possible to execute it either.
I prefer @0 agaisnt @1 because workflow is simple and robust. If unnamed PP doesn't exists, then it will be created, else it will be replaced. @1 has little bit more complex workflow, because there is not command like DEALLOCATE IF EXISTS, so I have to ensure deallocation in all possible ways.
ISTM That it is only of the PQprepare succeeded, so there should be only one point, at the end of the corresponding OK condition?
Another reason for @0 is not necessity to generate some auxiliary name.
Yes. I do not like special names either. But I do not like keeping objects lives if they are dead. Not sure which is worst.
My opinion in this case is not too strong - just I see the advantages of @0 (robust and simple) nice. The question is about cost of unwanted allocated PP to end of session.
My opinion is not strong either, it is more the principle that I do not like to let things forever live in the server while they are known dead.
Hmmm. Strange. For some obscure reason, the unnamed prepared statement does not show in pg_prepared_statements:
looks like the design. Unnamed PP is near to PP created by PLpgSQL.
calvin=# PREPARE test AS SELECT 2; calvin=# EXECUTE test; -- 2 calvin=# SELECT 1 AS one \gdesc -- one | integer calvin=# SELECT * FROM pg_prepared_statements ; -- just one row: -- test | PREPARE test AS SELECT 2; │7..
Conclusion: Maybe let it as solution 0 for the time being, with a comment telling that it will be cleaned on the next unnamed PQprepare, and the committer will have its opinion.
good decision.
Thank you for review. I'll send new version early.
