Re: send Describe Portal message in PQsendPrepare

From: Manlio Perillo <manlio(dot)perillo(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: PGSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: send Describe Portal message in PQsendPrepare
Date: 2013-02-12 12:00:57
Message-ID: 511A2EF9.50109@gmail.com
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Il 11/02/2013 22:39, Tom Lane ha scritto:
> Manlio Perillo <manlio(dot)perillo(at)gmail(dot)com> writes:
>> What is the reason why PQsendPrepare function does not send a
>> Describe Portal message?
>
> That would add a round trip, no?
>

Well, no.

An extra round trip is required with current implementation, since I
need to call PQsendPrepare, wait for server response, call
PQsendDescribePrepared, wait for server response.

>> Sending a Describe Portal message, make it possible for PQsendPrepare
>> function to *return* a PGresult with more useful informations, instead
>> of just the result status.
>
> That's *definitely* wrong, because the entire point of the PQsend
> functions is they don't wait for a server response.
>

The PQsendQueryParams sends the following protocol messages:

* Parse
* Bind
* Describe Portal
* Execute
* Sync

and of course does not wait for each response, since this is done in the
state machine.

I noted that PQsendQueryParams sends a Describe Portal message, and I
found it strange that the same is not done by PQsendPrepare.

I wrote the patch to check if this was done due to some technical
reason, but this seems to not be the case.

> regards, tom lane

Regards Manlio Perillo
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