From: | Aleksey Dashevsky <postgres(at)luckynet(dot)co(dot)il> |
---|---|
To: | Lendvary Gyorgy <gyurika(at)prolan(dot)hu> |
Cc: | pgsql-sql(at)postgreSQL(dot)org |
Subject: | Re: [SQL] update by one transaction |
Date: | 1998-06-11 08:54:19 |
Message-ID: | Pine.LNX.3.96.SK.980611114949.20390A-100000@kesha.luckynet.co.il |
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Lists: | pgsql-sql |
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.
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