I want to add one point to this discussion: There is not just JDBC - other connection pools or clients might want different behaviour (which can from my point of view only lead to a complete reset).
If the JDBC driver prefers different behaviour (maybe for prepared statements) we should discuss further options for RESET.
Now there is: RESET CONNECTION (cleaning entire connection), RESET ALL (cleaning GUCS only) and RESET some_guc.
Maybe we want RESET LISTENER, RESET PREPARED, RESET CURSORS.
Personally I think this is not a good idea.
Karel Zak wrote:
On Mon, 2005-01-03 at 20:27 -0500, Tom Lane wrote:
I'm inclined to think that we'd have to add a protocol message that reports RESET CONNECTION to really answer objections of this type. That seems to bring the thing into the category of "stuff that forces a protocol version bump" :-(
Perhaps RESET CONNECTION should be a protocol-level operation instead of a SQL command? That would prevent user-level code from causing it without the driver knowing.
I still don't see a big difference between DEALLOCATE and RESET -- both can break the JDBC driver. I'm not sure if we need prevent bad usage of PG tools (JDBC in this case). The DEALLOCATE/RESET usage is under user's full control and everything can be described in docs.
I think each PG command returns some status. For example in libpq it's possible check by PQcmdStatus(). I think JDBC can checks this status (by own PQcmdStatus() implementation) and if PG returns string "CONNECTION- RESETED" it can deallocate internal stuff. This solution doesn't require touch the protocol.
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