Re: Please help - tks - Mailing list pgsql-admin

Brett,

  It appears that I may have upset you somehow.  I didn't intend to.  I
chose to write the PERL script to place them in a transaction to help
improve performance a little bit on each pass.  By building and tearing
down a connection to the postmaster everytime you send an update, you will
be putting a much heavier load on the server than is necessary.  If I was
using the script myself, I would make the connection to the postmaster
once at the top of the script, and then re-use it with a transaction block
for each group of 10/20.  Then shut it down at the end.  This way I do not
suffer any additional protocol overhead each time I want to use it.

- brian


On Thu, 18 Oct 2001, Brett Schwarz wrote:

> ????
>
> This is why I said this:
> > > adjust the sleep to your own specs.
>
> If he wants to "batch" them, then all he needs to do is add a condition/count:
>
> --------------------------------
> #!/bin/sh
>
> cnt=1
> while read line; do
>
>     # "batches" of 20 or whatever you *want*
>     if [ "X$cnt" == "X20" ]; then
>         sleep 5   # whatever you *want*
>         cnt=0
>     fi
>
>     psql dbname -c "UPDATE ... $line ..."
>     let cnt=$cnt+1
>
> done < filename
>
> ---------------------------------
>
> I will leave it up to the reader to modify this to his/her *specific* need...
>
> --brett
>
>
>
>
> On Thu, 18 Oct 2001 20:07:32 -0500 (CDT)
> Brian McCane <bmccane@mccons.net> wrote:
>
> > Much too quick and dirty.  With 300,000 updates this will take 1.5million
> > seconds, roughly 200 days.  Even at a rate of 1 a second it will take
> > nearly four days.  All this aside, I would probably use a perl script and
> > do batches of about 10-20, with a sleep.  You can try something like the
> > following and feed it using standard input.  Please NOTE, I didn't test
> > this, and even if I did, you shouldn't trust me :).
> >
> > - brian
> >
> > Wm. Brian McCane                    | Life is full of doors that won't open
> > Search http://recall.maxbaud.net/   | when you knock, equally spaced amid those
> > Usenet http://freenews.maxbaud.net/ | that open when you don't want them to.
> > Auction http://www.sellit-here.com/ | - Roger Zelazny "Blood of Amber"
> >
> > #! /usr/bin/perl
> >
> > use strict ;
> >
> > my @updates ;
> >
> > while (my $line = <STDIN>)
> > {
> >   my $cmd = "UPDATE table SET ......." ;    # Use the line we just read
> >   push(@updates, $cmd) ;
> >   if (@updates == 10)
> >   {
> >     do_update() ;
> >     sleep 5 ;
> >     @updates = () ;                # Redundant
> >   }
> > }
> > do_update if (@updates) ;
> >
> > sub do_update
> > {
> >   open PSQL, "| psql dbname" ;
> >   print PSQL "begin transaction ;\n" ;
> >   while (my $cmd = shift @updates)
> >   {
> >     print PSQL $cmd . "\n" ;
> >   }
> >   print PSQL "commit ;\n" ;
> >   close PSQL ;
> > }
> >
> > __END__
> >
> >
> > On Thu, 18 Oct 2001, Brett Schwarz wrote:
> >
> > > A quick and dirty solution would be something like (untested):
> > >
> > > while read line; do
> > >     psql dbname -c "update table  ... use 'line' as your id and data"
> > >     sleep 5
> > > done < filename
> > >
> > > where "filename" is the file with the ids in it. "dbname" is the name of your DB (of course!)
> > >
> > > I am not sure what your file looks like, but you can do something like this. It could be easy, or harder,
dependingon what your file has. 
> > >
> > > adjust the sleep to your own specs.
> > >
> > > --brett
> > >
> > >
> > > P.S.
> > >
> > > You could test this out by doing:
> > >
> > > while read line; do
> > >     psql dbname -c "select * from table where id=$line"
> > >     sleep 5
> > > done < filename
> > >
> > >
> > >
> > > On Thu, 18 Oct 2001 16:35:01 +1000 (EST)
> > > Mr OCP <mr_ocp@yahoo.com> wrote:
> > >
> > > > Hi Folks
> > > >
> > > > We have about 300,000 records to update, I have
> > > > created a file with the ids of the records to be
> > > > updated, since the number of records to be updated is
> > > > very large, the update statement takes forever and
> > > > server slows down dramatically, therefore I want to do
> > > > one at a time.
> > > >
> > > > Do you guys have any script which may update records
> > > > one by one using the file that lists these records. I
> > > > am running postgresql sever under Unix, any kind of
> > > > script would do, whether its a perl, bash or sql
> > > > whatever script
> > > >
> > > > Thanks for your help
> > > > Mike
> > > >
> > > > http://briefcase.yahoo.com.au - Yahoo! Briefcase
> > > > - Manage your files online.
> > > >
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