Re: Ajax/PostgreSQL

Paul M Foster wrote:
> I'm doing some massive (internal company) applications using PHP, which
> query extensive PostgreSQL tables. This is fine, but obviously it often
> requires multiple web pages to get something done. Supposedly, AJAX
> promises to make web pages more interactive. But from what I understand,
> I'd have to have bindings from Javascript into PostgreSQL to make this
> work.
>
> Here's an example: The user wants to enter a bill (accounts payable)
> into the system. He first has to pick a vendor. Normally, this would
> entail a PHP page that generates a PostgreSQL query. The user would then
> get a second page with various vendor information (like number of due
> days for that vendor), and various other payable info. But wouldn't it
> be nice to have vendor information filled in on the original page,
> directly after the user picks a vendor? Theoretically, AJAX might allow
> something like this. But from what I can see, it would require
> PostgreSQL bindings in Javascript, and some way to pass the data back so
> that PHP could use it.
>
> Is this even possible? Is it being worked on? Is there a different
> solution I don't know about? I can see where Javascript can alter the
> look of a page, but I can't work out how it would allow interactive use
> of a PostgreSQL table.
>
No - AJAX is really talking about the ability to use client-side JavaScript to
request XML documents from a server.

In this case if you want to have a page show vendor information when a user
selects a specific vendor, then your client-side JavaScript would request a
resource on your server that will return that information in XML.

If you're using PHP then the request you might make might be something like:
http:/myserver.com/getVendorInfo.php

The PHP request on the server goes to Postgres and retrieves the appropriate
information, formats it as XML and writes it out like any other page.

The client-side Javascript gets the XML response, uses client-side DOM to decode
the response and changes the page HTML to include the appropriate information
without having the page do a refresh.

Obviously this is often not much faster than getting a different page, and is
one of the fundamental problems with things like AJAX and SOA - each remote
request is remote - it has to go over the internet and suffers not only the
processing time at the database but also the network latency.

But to answer your question - there is *not* coupling between JavaScript and
Postgres. The JavaScript runs on the client, Postgres on the server and PHP as
your intermediary.

Best regards
Pete
--
Peter Wilson
YellowHawk Ltd (http://www.yellowhawk.co.uk)
Server Side XML and Javascript Web Application Server - http://www.whitebeam.org