Re: Storing images in a db (for web/midlet access)

You need to create a servlet (or the equivalent in ASP, PHP etc) that
sits between the clients browser and your database. In this layer you
implement a cache. The first time the image is requested you retrieve it
from the database and serve it normally, but you also copy the byte
stream to your cache (possibly using the image URL as your cache key).

The next time the image is requested, you check the cache first to see
if you can serve the image directly from there, otherwise you go back to
the database again.

If you're using java, looked at implementing a LRU cache using
LinkedHashMap, and you'll need to read up on HttpResponseWrappers to
intercept the byte stream and write it to your cache.

Also keep details of the modification date of the image resource, size
and the "etag". You may find a client making a HEAD request to check
that the image hasn't changed - serving this data from your cache will
definitely yield a performance boost as the client won't then need to
request the image.

Caching is no silver bullet if you're serving hundreds/thousands of
different images in a short time frame and your cache size is memory
limited as you may find that you are not be able to hold images in
memory long enough to make the cache viable.

This is not a postgres issue so much as a web application design issue.
You may be better off directing your questions to a list more
appropriate for the web technology you are using.

John

Assad Jarrahian wrote:
> Hi All,
> So I am trying to store images in the db which will be accessed from
> a midlet and website.
> So I looked into generating temp files, such as the one done here
> using servlets (http://fdegrelle.over-blog.com/categorie-275139.html).
> What I am confused about is that this may not be very efficient.
> When one browses a website, the pages (and hence the images) are
> basically cached in the browser, but with this method, it seems that
> every access to an image (that has already been viewed in a web
> session) is going to cause a re-query to the database. Not that
> efficient, no?
> Is there another way around that will help me take advantage of
> caching etc, just like it would with storing images on fs?
> Much thanks in advance!
>
> -Assad
>
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