update by one transaction - Mailing list pgsql-sql

From Lendvary Gyorgy
Subject update by one transaction
Date
Msg-id 357F925F.6299EB1C@prolan.hu
Whole thread Raw
Responses Re: [SQL] update by one transaction  (Aleksey Dashevsky <postgres@luckynet.co.il>)
List pgsql-sql
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!

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