Обсуждение: PHP and PostgreSQL question on identifier limits.

Hello,

I am migrating from MySQL to PostgreSQL and ran into a limitation of
PostgreSQL. I ran into this because of a technique I use for displaying
results of a SELECT query. In some cases I like to have the heading of some
columns in the table be clickable, usually to sort output by that column.

I have common a function I use that displays the results of a query in an HTML
table with the column headings being the field names. Here is a snippet of
code showing a typical query:

=======================================================
$_GET['sort'] && $_SESSION['sort']=$_GET['sort'];
$sort=$_SESSION['sort'];
$sort || $sort="field1";

$query="SELECT
field1 AS \"<a href=$PHP_SELF?sort=field1>field1</a>\",
field2 AS \"<a href=$PHP_SELF?sort=field2>field2</a>\",
field3 AS \"<a href=$PHP_SELF?sort=userid>field3</a>\"
FROM my_table ORDER BY $sort";

$tbl=new Table($query);
$tbl->print();
=======================================================

The problem I ran into is when the "AS" exceeds 63 characters --- which it
does NOT in the above example, but sometimes DOES in more complex real-life
queries. In those cases I get a PostgreSQL error saying that the identifier
is too long. Looking at the PostgreSQL documentation I see this is set to 63
characters by default but can be changed with a recompile.

Before I recompile PostgreSQL I would like to re-think my strategy for making
column headings clickable links.

Does anyone else create HTML tables with clickable headers? If so, do you use
a similar or different technique?

--
Robert C. Paulsen, Jr.
robert@paulsenonline.net

Hi,

> $_GET['sort'] && $_SESSION['sort']=$_GET['sort'];
> $sort=$_SESSION['sort'];
> $sort || $sort="field1";

First of all I don't feel very comfortable with this exotic syntax, but
this is not the right place to discuss about it ;)


> $query="SELECT
> field1 AS \"<a href=$PHP_SELF?sort=field1>field1</a>\",
> field2 AS \"<a href=$PHP_SELF?sort=field2>field2</a>\",
> field3 AS \"<a href=$PHP_SELF?sort=userid>field3</a>\"
> FROM my_table ORDER BY $sort";
>
> $tbl=new Table($query);
> $tbl->print();

Is there a good reason why you don't add hyperlinks inside your Table
class, instead than using column names for such a purpose?


P.S.
Handling column sorting like you're doing is a big security risk! I hope
you are doing some more checks on $sort, otherwise SQL injection attacks
would be very easy to do.


Best regards
--
Matteo Beccati
http://phpadsnew.com/
http://phppgads.com/

On Sunday 15 August 2004 06:58 pm, Matteo Beccati wrote:
> Hi,
>
> > $_GET['sort'] && $_SESSION['sort']=$_GET['sort'];
> > $sort=$_SESSION['sort'];
> > $sort || $sort="field1";
>
> First of all I don't feel very comfortable with this exotic syntax, but
> this is not the right place to discuss about it ;)
>

I guess "exotic" depends on your background.

> > $query="SELECT
> > field1 AS \"<a href=$PHP_SELF?sort=field1>field1</a>\",
> > field2 AS \"<a href=$PHP_SELF?sort=field2>field2</a>\",
> > field3 AS \"<a href=$PHP_SELF?sort=userid>field3</a>\"
> > FROM my_table ORDER BY $sort";
> >
> > $tbl=new Table($query);
> > $tbl->print();
>
> Is there a good reason why you don't add hyperlinks inside your Table
> class, instead than using column names for such a purpose?

That might be the best solution. This code has evolved from a time before I
was using classes. Used to be a simple function call. With classes I could
add the ability to assign links to the headers.

>
>
> P.S.
> Handling column sorting like you're doing is a big security risk! I hope
> you are doing some more checks on $sort, otherwise SQL injection attacks
> would be very easy to do.

Good point. Using your suggestion about implementing this inside the Table
class will make this easier to control.

--
Robert C. Paulsen, Jr.
robert@paulsenonline.net