Horton

Thread

  1. Re: TOAST and TEXT

    Chris Bitmead <chris@bitmead.com> — 2001-10-11T05:24:33Z

     >Chris Bitmead <chris@bitmead.com> writes:
 >> ... I don't
 >> like the old large object implementation, I need to store very large
 >> numbers of objects and unless this implementation has changed
 >> in recent times it won't cut it.
 >
 >Have you looked at 7.1?  AFAIK it has no particular problem with
 >lots of LOs.
 >
 >Which is not to discourage you from going over to bytea fields instead,
 >if that model happens to be more convenient for your application.
 >But your premise above seems false.

I'm storing emails, which as we know are usually small but occasionally 
huge. OK, I see in the release notes something like "store all large
objects in one table". and "pg_dump" of large objects. That sounds like
maybe LOs are now ok, although for portability with Oracle blobs it
would be nice if they could be embedded in any row or at least appear
to be so from client interface side (Java client for what I'm doing).

BTW, the postgres docs web pages says there is "no limitation" on row
size. Someone should probably update that with the info given in the
last few emails and probably integrate it in the regular doco as well.

  2. Suitable Driver ?

    Balaji Venkatesan <balaji.venkatesan@megasoft.com> — 2001-10-11T06:18:09Z

    HI
        I have to setup PERL to interact with PGSQL.
        I have taken the following steps.

        1.Installation of perl_5.6.0 under Redhat Linux 7.0
        2.Installation of POSTGRESQL under Redhat Linux7.0

        Both are working perfectly as seperate modules.

        Now I need to interface perl with PGSQL.

        I need to what's the best possible soln.

        I have installed latest DBI from www.cpan.org

        Now i need to install DBD For PGSQL .Is
        this the driver i have to work on for pgsql ?.
        Or do I have any other option to connect to pgsql
        from perl . Indeed i've found out an other way
        to use Pg driver provided by PGSQL to interface
        perl with pgsql.

        I need to exactly know the difference between
        use Pg ; and use DBI ; Need to which one is
        proceeding towards correct direction under what circumstances.


        when I tried to install DBD-Pg-0.93.tar.gz under Linux
        i get

        Configuring Pg
        Remember to actually read the README file !
        please set environment variables POSTGRES_INCLUDE and POSTGRES_LIB !

        I need to know what these varibles POSTGRES_INCLUDE and POSTGRES_LIB
        should point to ...

        and when i tried to run perl test.pl, the program to test the
installation of the module which
        comes with the tar.
         I get the error

        OS: linux
        install_driver(Pg) failed: Can't locate DBD/Pg.pm in @INC (@INC
contains: /usr/l
        ib/perl5/5.6.0/i386-linux /usr/lib/perl5/5.6.0
/usr/lib/perl5/site_perl/5.6.0/i3
        86-linux /usr/lib/perl5/site_perl/5.6.0 /usr/lib/perl5/site_perl .)
at (eval 1)
        line 3.
        Perhaps the DBD::Pg perl module hasn't been fully installed,
        or perhaps the capitalisation of 'Pg' isn't right.
        Available drivers: ADO, ExampleP, Multiplex, Proxy.
         at test.pl line 51

        Any body who can clarify is most welcome....

        with regards,
        Prassanna...

  3. Re: Suitable Driver ?

    alex@pilosoft.com — 2001-10-11T14:11:42Z

    On Thu, 11 Oct 2001, Balaji Venkatesan wrote:

>         Now i need to install DBD For PGSQL .Is
>         this the driver i have to work on for pgsql ?.
>         Or do I have any other option to connect to pgsql
>         from perl . Indeed i've found out an other way
>         to use Pg driver provided by PGSQL to interface
>         perl with pgsql.
You need DBD::Pg, which is a DBD driver for postgres.

> 
>         I need to exactly know the difference between
>         use Pg ; and use DBI ; Need to which one is
>         proceeding towards correct direction under what circumstances.
You need use DBI; and use DBD::Pg;
Pg by itself is slightly lower-level module that is similar to C interface
to postgresql.

>         when I tried to install DBD-Pg-0.93.tar.gz under Linux
>         i get
> 
>         Configuring Pg
>         Remember to actually read the README file !
>         please set environment variables POSTGRES_INCLUDE and POSTGRES_LIB !
> 
>         I need to know what these varibles POSTGRES_INCLUDE and POSTGRES_LIB
>         should point to ...
To location of your installed postgres includes' and libraries
For example:

export POSTGRES_INCLUDE=/usr/local/pgsql/include
export POSTGRES_LIB=/usr/local/pgsql/lib

-alex

  4. Re: Suitable Driver ?

    Tom Lane <tgl@sss.pgh.pa.us> — 2001-10-11T16:24:42Z

    "Balaji Venkatesan" <balaji.venkatesan@megasoft.com> writes:
>         I have installed latest DBI from www.cpan.org
>         Now i need to install DBD For PGSQL .Is
>         this the driver i have to work on for pgsql ?.

If you want to use DBI then you should get the DBD::Pg driver from
CPAN.  (Yes, it is on CPAN, even though their index page about DBD
modules didn't list it last time I looked.)

>         I need to exactly know the difference between
>         use Pg ; and use DBI ; Need to which one is

Pg is a older stand-alone driver; it's not DBI-compatible,
and it's got nothing to do with DBD::Pg.

			regards, tom lane

  5. Re: TOAST and TEXT

    Bruce Momjian <pgman@candle.pha.pa.us> — 2001-10-13T03:38:06Z

    > BTW, the postgres docs web pages says there is "no limitation" on row
> size. Someone should probably update that with the info given in the
> last few emails and probably integrate it in the regular doco as well.

Although the field length is limited to 1GB, is there a row size limit? 
I don't know of one.  The FAQ does say below the list:

    Of course, these are not actually unlimited, but limited to
    available disk space and memory/swap space. Performance may suffer
    when these values get unusually large. 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

  6. Re: TOAST and TEXT

    Tom Lane <tgl@sss.pgh.pa.us> — 2001-10-13T03:56:09Z

    Bruce Momjian <pgman@candle.pha.pa.us> writes:
> Although the field length is limited to 1GB, is there a row size
> limit? 

Sure.  1Gb per field (hard limit) times 1600 fields (also hard limit).
In practice less, since TOAST pointers are 20bytes each at present,
meaning you can't have more than BLCKSZ/20 toasted fields in one row.

Whether this has anything to do with real applications is debatable,
however.  I find it hard to visualize a table design that needs several
hundred columns that *all* need to be GB-sized.

			regards, tom lane

  7. Re: TOAST and TEXT

    Bruce Momjian <pgman@candle.pha.pa.us> — 2001-10-13T04:13:32Z

    > Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > Although the field length is limited to 1GB, is there a row size
> > limit? 
> 
> Sure.  1Gb per field (hard limit) times 1600 fields (also hard limit).
> In practice less, since TOAST pointers are 20bytes each at present,
> meaning you can't have more than BLCKSZ/20 toasted fields in one row.

I read this as 409GB with 8k pages.

> Whether this has anything to do with real applications is debatable,
> however.  I find it hard to visualize a table design that needs several
> hundred columns that *all* need to be GB-sized.

Yes, that just makes my head hurt.  Easier to just say "unlimited" and
limited by your computer's memory/disk.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026