Re: best performance for simple dml

forgive me for brain storming a little re copy:
if there are a limited number of tables you're inserting, would there be anything wrong with the app opening a copy connection?  ie, a connection initiates the copy and then stays open like a pipe for any inserts coming through it.  visually it's a very cool paradigm, but is it actually a good idea?
--- On Mon, 6/27/11, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Subject: Re: [SQL] best performance for simple dml
To: "chester c young" <chestercyoung(at)yahoo(dot)com>
Cc: pgsql-sql(at)postgresql(dot)org
Date: Monday, June 27, 2011, 1:05 AM

2011/6/27 chester c young <chestercyoung(at)yahoo(dot)com>
>
> two questions:
> I thought copy was for multiple rows - is its setup cost effective for one row?

I expect it will be faster for one row too - it is not sql statement

if you want to understand to performance issues you have to understand to

a) network communication costs
b) SQL parsing and SQL planning costs
c) commits costs
d) other costs - triggers, referential integrity costs

>
> copy would also only be good for insert or select, not update - is this right?

sure,

If you need to call a lot of simple dml statement in cycle, then

a) try tu move it to stored function
b) if you can't to move it, then ensure, so statements will be
executed under outer transaction

slow code

for(i = 0; i < 1000; i++)
  exec("insert into foo values($1), itoa(i));

10x faster code

exec('begin');
for(i = 0; i < 1000; i++)
  exec("insert into foo values($1), itoa(i));
exec('commit');

Regards

Pavel Stehule

>
> --- On Mon, 6/27/11, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
>
> From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
> Subject: Re: [SQL] best performance for simple dml
> To: "chester c young" <chestercyoung(at)yahoo(dot)com>
> Cc: pgsql-sql(at)postgresql(dot)org
> Date: Monday, June 27, 2011, 12:35 AM
>
> Hello
>
> try it and you will see. Depends on network speed, hw speed. But the most fast is using a COPY API
>
> http://www.postgresql.org/docs/9.0/interactive/libpq-copy.html
>
> Regards
>
> Pavel Stehule
>
>
> 2011/6/27 chester c young <chestercyoung(at)yahoo(dot)com>
>
> what is the best performance / best practices for frequently-used simple dml, for example, an insert
> 1. fast-interface
> 2. prepared statement calling "insert ..." with binary parameters
> 3. prepared statement calling "myfunc(..." with binary parameters; myfunc takes its arguments and performs an insert using them
>