Re: optimal insert - Mailing list pgsql-sql

And don't forget that \COPY and especially COPY are usually much faster
(and, IMHO, easier to compose/maintain) than gobs of INSERTs.


> -----Original Message-----
> From: pgsql-sql-owner@postgresql.org
> [mailto:pgsql-sql-owner@postgresql.org] On Behalf Of Aaron Bono
> Sent: Tuesday, October 10, 2006 1:46 PM
> To: Dirk Jagdmann
> Cc: pgsql-sql@postgresql.org
> Subject: Re: [SQL] optimal insert
>
> On 10/8/06, Dirk Jagdmann <jagdmann@gmail.com> wrote:
>
>     Hello experts,
>
>     I have a database that contains three tables:
>
>     create table a (
>     id serial primary key,
>     ... -- some more fields not relevant for my question
>     );
>     create table b (
>     id serial primary key,
>     ... -- some more fields not relevant for my question
>     );
>     create table a_b (
>     a int not null references a,
>     b int not null references b
>     );
>
>     Tables a and b have already been filled with lots of
> rows. Now my
>     application needs to insert the relationship of a to b
> into table a_b
>     and is currently doing it with inserts like the following:
>
>     insert into a_b(a,b) values(1,100);
>     insert into a_b(a,b) values(1,200);
>     insert into a_b(a,b) values(1,54);
>     insert into a_b(a,b) values(1,4577);
>
>     So for a batch of inserts the value of a stays the
> same, while for by
>     arbitrary values are inserted. Now I have wondered if
> PostreSQL offers
>     a smarter way to insert those values? A solution can
> contains usage of
>     some plpgsql code.
>
>
> It depends on your logic.  If you can write a query that
> selects out the a and b records, there is a smart way:
>
> insert into a_b(a, b)
> select 1, b.id from b where b.id in (100, 200, 54, 4577);
>
> This is not really smart because you already have the id
> values - the select may diminish your performance rather than
> help.  But if the select is "smarter" then you don't even
> need to know what the b.id <http://b.id>  values are:
>
> insert into a_b(a, b)
> select 1, b.id from b where b.somecolumn = 'somevalue';
>
> Hope this helps.
>
>
>
> ==================================================================
>        Aaron Bono
>        Aranya Software Technologies, Inc.
>        http://www.aranya.com
>        http://codeelixir.com
>
> ==================================================================
>
>