in reply to Re: Re: Another Opinion Request...(config file)
in thread Another Opinion Request...(config file)

Let me see if I can make this a bit more clear. After your comments I can see how you might have been confused. Now, after 5 hours of meetings, this might get more confusing but lets hope not.

By adding a field to the table that you want to store your generic "name" and "value" fields into - you increase it's ability to accept values for different reasons exponentially (or is it geometrically?). My suggestion is to add another field - call it "type". This new field would contain a value that you could use to group all your variables together with. Kinda like tieing a bunch of sticks together so that when you grab the bunch your get them all - same idea with the data fetching routine - grab them by "type" not by variable name. If you do this you limit the Disk I/O and optimize the use of buffering available for which ever data base engine you are using.

This new field now groups all your variables - you fetch them (using your WHERE clause by including the new "type" field). Once you have all your vairables - you can allow the user to alter them in any fashion you wish. Or for that matter, the program can alter them in any fashion it wishes.

Ok - with that understanding - now you can extend any database table without having to specifically add new fields to existing tables - you simply add data to an already existing table - this new data allows you to group, identify and quantify the new field data. So - for instance - there is an already existing table named MonthlyStats - you need a field for MeanSales - you simple add a record in the the "other" table (the one you added "type" to) type = MonthlyStats, name - MeanSales, value=1,200,000.00.

If you add some "smart comments" into your code where you place these "hooks" - you can then later search and replace this code with code that looks at the parent table (the one you extended) - this of course assumes that the "quick fix" you did to avoid having to bring the database server down for maintenance to add a field earlier has at some point been done. Oh yeah - you would have to create a data migration utility to take the data from one table to the parent.

If this is still confusing (as I'm sure it is) - just drop me a note and I will forward you my phone number. Maybe I can explain this better in that context.

  • Comment on Re: Re: Re: Another Opinion Request...(config file)

Replies are listed 'Best First'.
Re: Another Opinion Request...(config file)
by powerhouse (Friar) on May 13, 2003 at 14:06 UTC
    Ok, I think I understand now... Let me see if I can make it clear, and please tell me if I am way off base or not... :o)

    Ok, I have these fields currently in my DB:
    name content
    I should add one called "type".

    Then when I call the variables I should do it in one big swipe:
    get_page_content("some_type");

    [download]
    Something like that, and it would then go load each value for that type?
    Here is how I currently do it:
    $default_font_family = get_page_content("default_font_family");

    [download]
    Each variables '$default_font_family' is the same name in the db: 'default_font_family'.
    So how could I do that, where it will take the "name" and make it a variable, without telling it like I do: 'name = sub('name');'
    Could I do something like this in the subroutine: 
        my $type = shift;
    my $dbh = DB_File::connect();
    $sth = $dbh->prepare (qq{ SELECT name,content FROM page_vars WHERE
+ type = ? });
    $sth->execute($type);
    while ( my ($db_name,$db_content) = $sth->fetchrow_hashref() ) {
        ${$db_name} = $db_content;
    }
    $sth->finish();
    return 1;

    [download]
    Would that work? I don't think it would, but I have not tried it. Do you know off hand if it would work?

    If not I suppose I could put them in a hash or array: 
        my $type = shift;
    my $dbh = DB_File::connect();
    $sth = $dbh->prepare (qq{ SELECT name,content FROM page_vars WHERE
+ type = ? });
    $sth->execute($type);
    my %vars;
    while (my ($db_name,$db_content) = $sth->fetchrow_hashref()) {
        $vars{$db_name} = $db_content;
    }
    $sth->finish();
    return(%vars);

    [download]
    Then I could just have each variable instead of being called by the name be called by a hash:
    instead of doing: $default_font_family = ... do this: %vars = get_page_content("some_type");
    Then %vars would contain all the variables so I could print them by doing:
    $vars{default_font_family}
    The only bad thing about using the hash, is that I have already done a lot of work, where I don't do that, so I'd have to put a whole lot of time into search and replace :o)

    Anyways, did I understand it the way you meant it?

    Thank you much, as usual!
    Richard
[reply]
[d/l]
[select]
      Looks to me like you got it !

      I would take the approach of using the hash to store the key/value pairs which end up being your variables with their respective values.

      Please let me know how you make out with this.

[reply]
Re: Another Opinion Request...(config file)
by powerhouse (Friar) on May 13, 2003 at 17:46 UTC
    One quick question...

    What did you mean by this:
    >you simple add a record in the the "other" table
    >(the one you added "type" to)

    What is "other"? Is that a "type"?

    thx,
    Richard
[reply]
      Sorry - you are right - that wasn't too clear - kinda like muddy water. At any rate, the "other" table is the table that you store your name and value fields - where you are storing the variables.
[reply]

In Section Seekers of Perl Wisdom