Re: Libpq support for precision and scale

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Fernando Nasser <fnasser(at)redhat(dot)com>
Cc: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Fernando Nasser <fnasser(at)cygnus(dot)com>, pgsql-hackers(at)postgresql(dot)org, Liam Stewart <liams(at)cygnus(dot)com>
Subject: Re: Libpq support for precision and scale
Date: 2002-03-08 01:46:51
Message-ID: 25893.1015552011@sss.pgh.pa.us
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Fernando Nasser <fnasser(at)redhat(dot)com> writes:
> We have agreed to add another call to set a flag for including the
> metadata on the PQexec call (which would make it work like the
> PQexecIncludeMetadata described above). It will be in the REPOST patch.

That works for me. Among other things, it solves the problem where the
code that wants the metadata is a layer or two above the place that's
actually issuing PQexec. Setting a persistent option in the PGconn
object gets around the difficulty that the caller of PQexec may not know
metadata will be wanted later.

> Question: should it affect only the next PQexec(), or should we require
> the user to reset it?

It should be persistent till reset, see above.

> An even worse problem is that
> it'll fail entirely with a multi-query query string.

I'm still quite unhappy about this; it more or less destroys the layer
independence mentioned above. Please think harder. Perhaps it could
be set up so that metadata is only collected for the last result of a
query string, after you determine that there are no more results?
Which is still not great, but better than failing outright with
multi-query strings.

regards, tom lane

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