Обсуждение: update by one transaction

Hello,

I have tried to write my problem, but I think nobody couldn,t understand
it (because of my bad English, I think).

I have a table for instance boci (row_number int, col2 float, col3
float). The boci table has about 10000 rows.
I want to update col3 column of the table in every row with different
values. Desired values are in an array has 10000 elements. I want to be
the value of the col3 column in the first row equal to the first element
of the array and so on.
I've done it with a 'for' cycle, but it is very slow. I want to do
theese updates with one transaction.

Here is a little piece of my program:

for (i=0; i<10000; i++)
{
    sprintf(buff, "UPDATE boci SET col3 = %f WHERE row_number=%d",
array[i], i);
    PQexec(conn, buff);
}
PQexec(conn, "COMMIT");

This program is very, very slow. Is there any way making this program
much faster (for instance with CURSOR or 'block write' or something
else)? Please write me a little program that describes your ideas!

Thanks for your help in advance!

On Thu, 11 Jun 1998, Lendvary Gyorgy wrote:

> Hello,
>
> I have tried to write my problem, but I think nobody couldn,t understand
> it (because of my bad English, I think).
>
> I have a table for instance boci (row_number int, col2 float, col3
> float). The boci table has about 10000 rows.
> I want to update col3 column of the table in every row with different
> values. Desired values are in an array has 10000 elements. I want to be
> the value of the col3 column in the first row equal to the first element
> of the array and so on.
> I've done it with a 'for' cycle, but it is very slow. I want to do
> theese updates with one transaction.
>
> Here is a little piece of my program:
>
> for (i=0; i<10000; i++)
> {
>     sprintf(buff, "UPDATE boci SET col3 = %f WHERE row_number=%d",
> array[i], i);
>     PQexec(conn, buff);
> }
> PQexec(conn, "COMMIT");
>
> This program is very, very slow. Is there any way making this program
> much faster (for instance with CURSOR or 'block write' or something
> else)? Please write me a little program that describes your ideas!
>
> Thanks for your help in advance!
>
It seems you simply forgot to start transaction before the loop. So you
need to prepend this code with begin statement:

PQexec(conn, "BEGIN");

Hope, this will help!

Aleksey.