* Glenn Maynard (glennfmaynard@gmail.com) wrote:
> On Wed, Apr 22, 2009 at 5:51 PM, Stephen Frost <sfrost@snowman.net> wrote:
> > For a single column table, I wouldn't expect much either. With more
> > columns I think it would be a larger improvement.
>
> Maybe. I'm not sure why parsing "(1,2,3,4,5)" in an EXECUTE parameter
> should be faster than parsing the exact same thing in an INSERT,
> though.
Erm.. Prepared queries is about using PQexecPrepared(), not about
sending a text string as an SQL EXECUTE(). PQexecPrepared takes an
array of arguments. That gets translated into a Bind command in the
protocol with a defined number of parameters and a length for each
parameter being passed. That removes any need for scanning/parsing the
string sent to the backend. That's the savings I'm referring to.
If you weren't using PQexecPrepared() (and using psql, you wouldn't
be..), then the difference you saw was more likely planning cost.
> Of course, you still need to get it in that format. Be careful to
> include any parsing you're doing to create the binary date in the
> benchmarks. Inevitably, at least part of the difference will be costs
> simply moving from the psql process to your own.
Sure. What I recall from when I was working on this is that it wasn't
terribly hard to go from unix timestamps (epoch from 1970) to a PG
timestamp format (and there was nice example code in the backend) in
terms of CPU time.
Thanks,
Stephen