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From: Daniel Blanch Bataller <[email protected]>
To: Mariel Cherkassky <[email protected]>
Cc: Scott Marlowe <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: performance problem on big tables
Date: Wed, 16 Aug 2017 15:08:56 +0200
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See if the copy command is actually working, copy should be very fast from your local disk.


> El 16 ago 2017, a las 14:26, Mariel Cherkassky <[email protected]> escribió:
> 
> 
> After all the changes of the memory parameters the same operation(without the copy utility) didnt run much faster - it  took one minute less. I made a test with the copy command (without the 'with binary') and it took 1.5 hours to create the dumpfile in my local postgresql server. Then I tried to run the copy from the local dump and it is already running two hours and it didnt even finish. I looked at the server log and I saw that I run the copy command at 13:18:05, 3 minutes later checkpoint started and completed and there are no messages in the log after that. What can I do ? Improving the memory parameters and the memory on the server didnt help and for now the copy command doesnt help either.
> 
> 
> 
> 
> 2017-08-15 20:14 GMT+03:00 Scott Marlowe <[email protected] <mailto:[email protected]>>:
> On Tue, Aug 15, 2017 at 4:06 AM, Mariel Cherkassky
> <[email protected] <mailto:[email protected]>> wrote:
> > Hi,
> > So I I run the cheks that jeff mentioned :
> > \copy (select * from oracle_remote_table) to /tmp/tmp with binary - 1 hour
> > and 35 minutes
> 
> So 26G takes 95 minutes, or 27 MB/minute or 456k/second? Sound about
> right (it's early, I haven't had enough coffee please check my math).
> That's pretty slow unless you're working across pretty big distances
> with mediocre connections.  My home internet downloads about 100MB/s
> by comparison.
> 
> > \copy local_postresql_table from /tmp/tmp with binary - Didnt run because
> > the remote oracle database is currently under maintenance work.
> 
> You shouldn't need the remote oracle server if you've already copied
> it over, you're just copying from local disk into the local pgsql db.
> Unless I'm missing something.
> 
> > So I decided to follow MichaelDBA tips and I set the ram on my machine to
> > 16G and I configured the effective_cache memory to 14G,tshared_buffer to be
> > 2G and maintenance_work_mem to 4G.
> 
> Good settings. Maybe set work_mem to 128MB or so while you're at it.
> 
> > I started running the copy checks again and for now it coppied 5G in 10
> > minutes. I have some questions :
> > 1)When I run insert into local_postresql_table select * from
> > remote_oracle_table I insert that data as bulk to the local table or row by
> > row ?  If the answer as bulk than why copy is a better option for this case
> > ?
> 
> insert into select from oracle remote is one big copy, but it will
> take at least as long as copying from oracle to the local network
> took. Compare that to the same thing but use file_fdw on the file
> locally.
> 
> > 2)The copy from dump into the postgresql database should take less time than
> > the copy to dump ?
> 
> Yes. The copy from Oracle to your local drive is painfully slow for a
> modern network connection.
> 
> > 3)What do you think about the new memory parameters that I cofigured ?
> 
> They should be OK. I'm more worried about the performance of the io
> subsystem tbh.
> 

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