Blog concept: Sketchy optimisations

Recently a colleague was showing me a concept he was working on. He drafted a change in a fight against so-called 1+n-queries (actually for some reason unknown to me they're called n+1 queries, but my head isn't able to process the problem with just one more query after n queries…); in software development using ORMs like active record it is quite easy to make a single database request objects that when a presented within a view trigger other queries for every object because it has a relationship. Round trips to databases are generally bad as they take time.

For his change, he introduced a new class that we could seemingly reuse, with a just another (a bad code-smell) declaration of relations between objects and whether these should be preloaded when retrieving the primary object. This was in response to indeed a quite bad part of our code that entailed returning objects with counts of selected associations, but instead of counting these in the database, the current code was a…

Lazy loading the lazy way

Below is a simple, lazy, technique I applied in a collection management tool where its users wanted to browse over 10.000 images without scroll-hijacking or pagination. Sure, only the HTML weight several MB’s at once, but for this particular application used by professionals it is worth the weight. But performance was too heavily affected by downloading all these separate images.

So let’s have a look how I solved this.

What does the code below do?

You rightly guessed that it won’t display any image to say ~95% of the users. The 5% who have disabled Javascript however, will see it.

The 95% who do have Javascript can enjoy the image simply by moving the img tag out of the noscript tag using a bit of JavaScript:

ELEMENTS_QUERY = "noscript[data-lazy=\"lazy-load\"]"

decode_entities = (encodedString)->
   ## required for IE and Safari
   textArea = document.createElement('textarea')
   t...