Skip site navigation (1) Skip section navigation (2)

Re: Please help - tks

From: Brett Schwarz <brett_schwarz(at)yahoo(dot)com>
To: Brian McCane <bmccane(at)mccons(dot)net>
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: Please help - tks
Date: 2001-10-19 22:25:35
Message-ID: 20011019152535.76750be1.brett_schwarz@yahoo.com (view raw or flat)
Thread:
Lists: pgsql-admin
Sorry, my bad. I thought your whole point was in regards to the sleep command (which I really didn't understand why). However, your point about stressing the server is a very valid point, and I did not catch that in your earlier post.

My apologies for the misunderstanding...

--brett

p.s. it's been a bad day...


On Fri, 19 Oct 2001 09:42:52 -0500 (CDT)
Brian McCane <bmccane(at)mccons(dot)net> wrote:

> 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(at)mccons(dot)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 $cmd . "\n" ;
> > >   }
> > >   print PSQL "commit ;\n" ;
> > >   close PSQL ;
> > > }
> > >
> > > __END__
> > >
> > >
> > > On Thu, 18 Oct 2001, Brett Schwarz wrote:
> > >
> > > > A quick and dirty solution would be something like (untested):
> > > >
> > > > while read line; do
> > > > 	psql dbname -c "update table  ... use 'line' as your id and data"
> > > > 	sleep 5
> > > > done < filename
> > > >
> > > > where "filename" is the file with the ids in it. "dbname" is the name of your DB (of course!)
> > > >
> > > > I am not sure what your file looks like, but you can do something like this. It could be easy, or harder, depending on what your file has.
> > > >
> > > > adjust the sleep to your own specs.
> > > >
> > > > --brett
> > > >
> > > >
> > > > P.S.
> > > >
> > > > You could test this out by doing:
> > > >
> > > > while read line; do
> > > > 	psql dbname -c "select * from table where id=$line"
> > > > 	sleep 5
> > > > done < filename
> > > >
> > > >
> > > >
> > > > On Thu, 18 Oct 2001 16:35:01 +1000 (EST)
> > > > Mr OCP <mr_ocp(at)yahoo(dot)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.
> > > > >
> > > > > ---------------------------(end of broadcast)---------------------------
> > > > > TIP 5: Have you checked our extensive FAQ?
> > > > >
> > > > > http://www.postgresql.org/users-lounge/docs/faq.html
> > > >
> > > > _________________________________________________________
> > > > Do You Yahoo!?
> > > > Get your free @yahoo.com address at http://mail.yahoo.com
> > > >
> > > >
> > > > ---------------------------(end of broadcast)---------------------------
> > > > TIP 3: if posting/reading through Usenet, please send an appropriate
> > > > subscribe-nomail command to majordomo(at)postgresql(dot)org so that your
> > > > message can get through to the mailing list cleanly
> > > >
> > >
> > >
> > > ---------------------------(end of broadcast)---------------------------
> > > TIP 6: Have you searched our list archives?
> > >
> > > http://archives.postgresql.org
> >
> > _________________________________________________________
> > Do You Yahoo!?
> > Get your free @yahoo.com address at http://mail.yahoo.com
> >
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 5: Have you checked our extensive FAQ?
> 
> http://www.postgresql.org/users-lounge/docs/faq.html

_________________________________________________________
Do You Yahoo!?
Get your free @yahoo.com address at http://mail.yahoo.com


In response to

pgsql-admin by date

Next:From: Tom LaneDate: 2001-10-19 23:19:52
Subject: Re: [repost] pg_restore doesn't work with custom format?
Previous:From: Brett W. McCoyDate: 2001-10-19 21:21:26
Subject: Re: Rename of a Table Column

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group