8Ko limitation

Started by Xavier ZIMMERMANNover 25 years ago12 messages
#1Xavier ZIMMERMANN
xzimmermann@matra-ms2i.fr

Hi,

I am thinking about using postgreSQL to manage large geographic databases
connected to a GIS.
I would really appreciate if someone could give me some answers to those 3
questions :
what about performances with postgreSQL and large databases,
the object size limitation (8192 bytes) is really not acceptable for this
purpose. Is there a way or any hack to overpass it,
is the geographic index working well.

Thanks.

Xavier.

#2Karel Zak
zakkr@zf.jcu.cz
In reply to: Xavier ZIMMERMANN (#1)
Re: [HACKERS] 8Ko limitation

what about performances with postgreSQL and large databases,
the object size limitation (8192 bytes) is really not acceptable for this

Now you can change this limit in config.h, the possible range is
8Kb - 32Kb.

In new 7.1 version will this limit dead forever (see TOAST project).

And what is a "large database"? 1, 5 .. 10Gb? If yes, (IMHO) the PostgreSQL
is good choice.

Karel

#3Stephane Bortzmeyer
bortzmeyer@pasteur.fr
In reply to: Karel Zak (#2)
Re: Re: [HACKERS] 8Ko limitation

On Thursday 20 July 2000, at 10 h 0, the keyboard of Karel Zak
<zakkr@zf.jcu.cz> wrote:

And what is a "large database"? 1, 5 .. 10Gb? If yes, (IMHO) the PostgreSQL
is good choice.

Even on Linux? I'm studying a database project where the raw data is 10 to 20
Gb (it will be in several tables in the same database). Linux has a limit of 2
Gb for a file (even on 64-bits machine, if I'm correct). A colleague told me
to use NetBSD instead, because PostgreSQL on a Linux machine cannot host more
than 2 Gb per database. Any practical experience? (I'm not interested in "It
should work".)

#4Jules Bean
jules@jellybean.co.uk
In reply to: Stephane Bortzmeyer (#3)
Re: Re: [HACKERS] 8Ko limitation

On Thu, Jul 20, 2000 at 10:35:41AM +0200, Stephane Bortzmeyer wrote:

On Thursday 20 July 2000, at 10 h 0, the keyboard of Karel Zak
<zakkr@zf.jcu.cz> wrote:

And what is a "large database"? 1, 5 .. 10Gb? If yes, (IMHO) the PostgreSQL
is good choice.

Even on Linux? I'm studying a database project where the raw data is 10 to 20
Gb (it will be in several tables in the same database). Linux has a limit of 2
Gb for a file (even on 64-bits machine, if I'm correct). A colleague told me
to use NetBSD instead, because PostgreSQL on a Linux machine cannot host more
than 2 Gb per database. Any practical experience? (I'm not interested in "It
should work".)

Postgres splits large tables into multiple files.

Experience suggests it tends to split at around 1.1G (at least, that's
what it has done on my last project).

FWIW, the 2Gig limit doesn't exist on 64bit linux, AFAIK (at least, not
with a 64-bit happy libc; I can't remember if the patches made it into
the version we use in Debian).

Jules

--
Jules Bean | Any sufficiently advanced
jules@debian.org | technology is indistinguishable
jules@jellybean.co.uk | from a perl script

#5Karel Zak
zakkr@zf.jcu.cz
In reply to: Stephane Bortzmeyer (#3)
Re: Re: [HACKERS] 8Ko limitation

On Thu, 20 Jul 2000, Stephane Bortzmeyer wrote:

On Thursday 20 July 2000, at 10 h 0, the keyboard of Karel Zak
<zakkr@zf.jcu.cz> wrote:

And what is a "large database"? 1, 5 .. 10Gb? If yes, (IMHO) the PostgreSQL
is good choice.

Even on Linux? I'm studying a database project where the raw data is 10 to 20
Gb (it will be in several tables in the same database). Linux has a limit of 2
Gb for a file (even on 64-bits machine, if I'm correct). A colleague told me
to use NetBSD instead, because PostgreSQL on a Linux machine cannot host more
than 2 Gb per database. Any practical experience? (I'm not interested in "It
should work".)

I must again say: "The PostgreSQL is good choice" :-)

The postgres chunks DB files, not exist 2Gb limit here...

Karel

#6Tom Lane
tgl@sss.pgh.pa.us
In reply to: Jules Bean (#4)
Re: Re: [HACKERS] 8Ko limitation

Jules Bean <jules@jellybean.co.uk> writes:

A colleague told me to use NetBSD instead, because PostgreSQL on a
Linux machine cannot host more than 2 Gb per database. Any practical
experience? (I'm not interested in "It should work".)

Postgres splits large tables into multiple files.

Segmenting into multiple files used to have some bugs, but that was a
few versions back --- I think your colleague's experience is obsolete.
There are lots of people using multi-gig tables now.

It's presently still painful to manage a database that spans multiple
disks, however. (You can do it if you're willing to move files around
and establish symlinks by hand ... but it's painful.) There are plans
to make this better, but for now you might want to say that the
practical limit is the size of disk you can buy. Alternatively, if
your OS can make logical filesystems that span multiple disks, you
can get around the problem that way.

regards, tom lane

#7Tom Lane
tgl@sss.pgh.pa.us
In reply to: Karel Zak (#2)
Re: [HACKERS] 8Ko limitation

"Justin Hickey" <jhickey@impact1.hpcc.nectec.or.th> writes:

Will the geometric data types be TOASTable for 7.1?

Probably ... if I get around to it ... or someone else does
(yes, that's a hint).

regards, tom lane

#8Justin Hickey
jhickey@impact1.hpcc.nectec.or.th
In reply to: Karel Zak (#2)
Re: 8Ko limitation

Hello Karel

On Jul 20, 10:00am, Karel Zak wrote:

Subject: Re: [HACKERS] 8Ko limitation

what about performances with postgreSQL and large databases,
the object size limitation (8192 bytes) is really not acceptable for

this

Now you can change this limit in config.h, the possible range is
8Kb - 32Kb.

In new 7.1 version will this limit dead forever (see TOAST project).

We use Postgres to store polygons and I asked this same question before. The
reply I got was that the geometric data types were not guaranteed to be
converted to TOASTable data types (they were at the bottom of the list of types
to convert). They hinted that I could help them with this but I have no time.
Has this changed now? Will the geometric data types be TOASTable for 7.1?

--
Sincerely,

Jazzman (a.k.a. Justin Hickey) e-mail: jhickey@hpcc.nectec.or.th
High Performance Computing Center
National Electronics and Computer Technology Center (NECTEC)
Bangkok, Thailand
==================================================================
People who think they know everything are very irritating to those
of us who do. ---Anonymous

Jazz and Trek Rule!!!
==================================================================

#9Brook Milligan
brook@biology.nmsu.edu
In reply to: Stephane Bortzmeyer (#3)
Re: Re: [HACKERS] 8Ko limitation

Even on Linux? I'm studying a database project where the raw data is 10 to 20
Gb (it will be in several tables in the same database). Linux has a limit of 2
Gb for a file (even on 64-bits machine, if I'm correct). A colleague told me
to use NetBSD instead, because PostgreSQL on a Linux machine cannot host more
than 2 Gb per database. Any practical experience? (I'm not interested in "It
should work".)

Postgresql and NetBSD work fine together. NetBSD has not had a 2GB
file limit for _many_ years and has raidframe for configuring huge
disks from many small ones (as well as for normal raid stuff).

Cheers,
Brook

#10Erich
hh@cyberpass.net
In reply to: Stephane Bortzmeyer (#3)
Re: Re: [HACKERS] 8Ko limitation

Even on Linux? I'm studying a database project where the raw data is 10 to 20
Gb (it will be in several tables in the same database). Linux has a limit of 2
Gb for a file (even on 64-bits machine, if I'm correct). A colleague told me

Quoi?

On my RedHat6.2 system:

/dev/md0 14111856 257828 13137168 2% /raid

to use NetBSD instead, because PostgreSQL on a Linux machine cannot host more
than 2 Gb per database. Any practical experience? (I'm not interested in "It
should work".)

For a heavy-duty server, I would probably pick OpenBSD over Linux, but
both will work fine, and both can have filesystems far larger than
2gb.

e

#11Stephane Bortzmeyer
bortzmeyer@pasteur.fr
In reply to: Erich (#10)
Re: Re: [HACKERS] 8Ko limitation

On Thursday 20 July 2000, at 14 h 5, the keyboard of Erich <hh@cyberpass.net>
wrote:

Linux has a limit of 2
Gb for a file (even on 64-bits machine, if I'm correct).

...

Quoi?

On my RedHat6.2 system:

/dev/md0 14111856 257828 13137168 2% /raid

...

and both can have filesystems far larger than 2gb.

Read the message before replying: I wrote FILE and not FILESYSTEM.

#12Hannu Krosing
hannu@tm.ee
In reply to: Xavier ZIMMERMANN (#1)
Re: [HACKERS] 8Ko limitation

Xavier ZIMMERMANN wrote:

Hi,

I am thinking about using postgreSQL to manage large geographic databases
connected to a GIS.

...

is the geographic index working well.

AFAIK r-trees ar used for planar geometry.
perhaps there something in contrib for geographic (spherical)
coordinates.

--------
Hannu