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  • About Maximum number of columns

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    Hi All.
    I have a question about the Maximum number of columns in a table ?
    In FAQ for PostgreSQL,I can find this description :
    Maximum number of columns in a table?
    250-1600 depending on column types
    But , I want to know what type is 1600 limit , and what type is 250
    limit . it is important for me , thanks .
    Regards ,
    zhao xin
    (end of broadcast)
    TIP 3: Have you checked our extensive FAQ?

  • No.1 | | 539 bytes | |

    zhaoxin wrote:
    Hi All.

    I have a question about the Maximum number of columns in a table ?

    In FAQ for PostgreSQL,I can find this description :
    Maximum number of columns in a table?
    250-1600 depending on column types
    But , I want to know what type is 1600 limit , and what type is 250
    limit . it is important for me , thanks .

    Have you tried creating the columns you need in the type you need?

    What happens?

    Are you sure hundreds of columns in a table is the best design for your
    problem?

  • No.2 | | 821 bytes | |

    I have to face this trouble , it is not I want , but a historical problem .
    so , can you tell me ?

    Richard Huxton wrote:
    zhaoxin wrote:

    >>Hi All.
    >>
    >>I have a question about the Maximum number of columns in a table ?
    >>
    >>In FAQ for PostgreSQL,I can find this description :
    >Maximum number of columns in a table?
    >250-1600 depending on column types
    >>But , I want to know what type is 1600 limit , and what type is 250
    >>limit . it is important for me , thanks .

    Have you tried creating the columns you need in the type you need?

    What happens?

    Are you sure hundreds of columns in a table is the best design for your
    problem?

  • No.3 | | 441 bytes | |

    zhaoxin schrieb:
    I have to face this trouble , it is not I want , but a historical problem .
    so , can you tell me ?

    Try it out. I'd change the future of that history though.

    You can expect much better performany on virtually any
    RDBMS with appropriate schema.

    ++Tino

    PS: try to send text-only to mailinglists

    (end of broadcast)
    TIP 3: Have you checked our extensive FAQ?

  • No.4 | | 657 bytes | |

    zhaoxin wrote:
    I have to face this trouble , it is not I want , but a historical problem .
    so , can you tell me ?

    Sure, but you'll need to say what column-types you have.

    Below is a small script to generate a table with lots of columns.

    #!/bin/perl -w
    use strict;

    my $tbl = 'test_text';
    my $typ = 'text';
    my $num_cols = 1500;

    print "CREATE TABLE $tbl (\n";
    for (my $c=0; $c<$num_cols; $c++) {
    print " col$c $typ,\n";
    }
    print "PRIMARY KEY (col0)\n";
    print ");\n";
    exit;

    You can run it with something like:
    perl mk_script.pl | psql -Urichardh richardh

  • No.5 | | 1068 bytes | |

    Thu, Dec 22, 2005 at 07:22:12PM +0800, zhaoxin wrote:
    Hi All.

    I have a question about the Maximum number of columns in a table ?

    In FAQ for PostgreSQL,I can find this description :
    Maximum number of columns in a table?
    250-1600 depending on column types
    But , I want to know what type is 1600 limit , and what type is 250
    limit . it is important for me , thanks .

    I'm pretty sure I've read the reason for the limit somewhere in the
    source code, but I can't remember where. It's probably somewhere in
    I know
    that the exact upper limit isn't actually 1600 fields, it's more like
    1643 or something.

    But, as others have said, just try creating your table and see what
    happens. If it fails, you might be able to get it to work by increasing
    the block size.

    And as others have said, this is almost certainly a horrible schema that
    needs to be fixed, badly. Luckily, thanks to views and rules, you could
    probably fix it without actually changing any of the client code.

  • No.6 | | 1769 bytes | |

    Thu, 2005-12-22 at 10:10, Jim C. Nasby wrote:
    Thu, Dec 22, 2005 at 07:22:12PM +0800, zhaoxin wrote:
    Hi All.

    I have a question about the Maximum number of columns in a table ?

    In FAQ for PostgreSQL,I can find this description :
    Maximum number of columns in a table?
    250-1600 depending on column types
    But , I want to know what type is 1600 limit , and what type is 250
    limit . it is important for me , thanks .

    I'm pretty sure I've read the reason for the limit somewhere in the
    source code, but I can't remember where. It's probably somewhere in
    I know
    that the exact upper limit isn't actually 1600 fields, it's more like
    1643 or something.

    But, as others have said, just try creating your table and see what
    happens. If it fails, you might be able to get it to work by increasing
    the block size.

    And as others have said, this is almost certainly a horrible schema that
    needs to be fixed, badly. Luckily, thanks to views and rules, you could
    probably fix it without actually changing any of the client code.

    The limit has to do with the fact that all the "header" info for each
    column must fit in a single block (8K default).

    I seem to recall someone stating that increasing block size to 16k or
    32k could increase this number by about 2x or 4x. Not sure if it'll
    work, but it might be worth the effort if you're stuck keeping some
    legacy app happy long enough to replace it with a well designed system.

    to be able to travel back in time and smack people for designing 1600
    column tables :)

    (end of broadcast)
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