Re: fixing PQsetvalue()

From: Merlin Moncure <mmoncure(at)gmail(dot)com>
To: Andrew Chernow <ac(at)esilo(dot)com>
Cc: Dmitriy Igrishin <dmitigr(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Pavel Golub <pavel(at)microolap(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: fixing PQsetvalue()
Date: 2011-06-23 13:41:15
Message-ID: BANLkTi=YzyzT5tN9Y3CHdU+hfmm_vQcXXw@mail.gmail.com
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On Thu, Jun 23, 2011 at 7:54 AM, Andrew Chernow <ac(at)esilo(dot)com> wrote:
>>    you are creating as you iterate through.  This behavior was
>>    unnecessary in terms of what libpqtypes and friends needed and may (as
>>    Tom suggested) come back to bite us at some point. As it turns out,
>>    PQsetvalue's operation on results that weren't created via
>>    PQmakeEmptyResult was totally busted because of the bug, so we have a
>>    unique opportunity to tinker with libpq here: you could argue that you
>>
>> +1
>>
>> Exactly at this moment I am thinking about using modifiable
>> (via PQsetvalue) PGresult instead of std::map in my C++ library
>> for store parameters for binding to executing command.
>> I am already designed how to implement it, and I supposed that
>> PQsetvalue is intended to work with any PGresult and not only
>> with those which has been created via PQmakeEmptyResult...
>> So, I am absolutely sure, that PQsetvalue should works with
>> any PGresult.
>
> All PGresults are created via PQmakeEmptyPGresult, including libpqtypes.
>  Actually, libpqtypes calls PQcopyResult which calls PQmakeEmptyPGresult.
>
> It might be better to say a "server" result vs. a "client" result.
> Currently, PQsetvalue is broken when provided a "server" generated result.

er, right-- the divergence was in how the tuples were getting added --
thanks for the clarification. essentially your attached patch fixes
that divergence.

merlin

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