Re: What language is faster, C or PL/PgSQL?

If a C function was a call to multiple (unprepared) SQL statements, could PL/PGSQL's prepare-once plan caching have an advantage?

-----Original Message-----
From: pgsql-general-owner(at)postgresql(dot)org [mailto:pgsql-general-owner(at)postgresql(dot)org] On Behalf Of Bruce Momjian
Sent: February 5, 2013 12:06 AM
To: Merlin Moncure
Cc: Carlo Stonebanks; kescobar(at)estudiantes(dot)uci(dot)cu; pgsql-general(at)postgresql(dot)org
Subject: Re: [GENERAL] What language is faster, C or PL/PgSQL?

On Mon, Feb 4, 2013 at 08:33:02AM -0600, Merlin Moncure wrote:
> On Sat, Feb 2, 2013 at 11:36 AM, Carlo Stonebanks
> <stonec(dot)register(at)sympatico(dot)ca> wrote:
> > Here is an advantage Plpgsql has:
> > http://www.postgresql.org/docs/9.1/static/plpgsql-expressions.html
> >
> > I guess you can offset this by creating your own prepared statements in C.
> > Otherwise, I can t think of how C could be slower. I would choose C
> > for functions that don t have SQL statements in them e.g. math and
> > string processing.
>
> For cases involving data processing (SPI calls), C can be slower
> because pl/pgsql has a lot of optimizations in it that can be very
> easy to miss. I don't suggest writing backend C functions at all
> unless you are trying to interface with a C library to access
> functionality currently not exposed in SQL.

How is PL/pgSQL faster than C? I thought we had optimized PL/pgSQL to save parsed functions, but I don't see how that would help with queries, which use SPI. Am I missing something?

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +

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