And it's been around forever. If you're interested in high-speed processing, there's lots of good papers from that project (e.g. how to avoid creating branches, stuff like that).
Have you actually looked at or used the array stuff in postgres? It's pretty horrible syntactically and worse, very explicit in it's recommended use.
"Tip: Arrays are not sets; searching for specific array elements can be a sign of database misdesign. Consider using a separate table with a row for each item that would be an array element. This will be easier to search, and is likely to scale better for a large number of elements."
Searching an array is a pretty common task, Mongo does really well in its ability to search into objects in a document.
I had to laugh a little at one of the sample queries:
SELECT f1[1][-2][3] AS e1, f1[1][-1][5] AS e2
FROM (SELECT '[1:1][-2:-1][3:5]={{{1,2,3},{4,5,6}}}'::int[] AS f1) AS ss;
Yes I've looked at them. I use them every day.
The example you posted its difficult to parse because it deals with multidimensional arrays and also populating one in the inner query. The simple, and much more common case of one dimension arrays is very straightforward. Can you show me the equivalent in MongoDB?
About the performance/scalability warning; I don't deal with very large arrays, a couple hundred items max, and when using a GIN index over the array field, search queries are screamingly fast.
Cycling puts an unnatural curve in our lower back, very similar to sitting in a chair, and due to the way the muscles work, cyclist end up with tight hip flexors and hamstrings and stretched spinal erectors (sorry, I've been out of Physiology for a while so can't remember the exact names of the muscles) which can further exacerbate the problem. Compare a cyclist with a runner, and you can see a noticeable difference in posture.
However, I wouldn't call it a 'negative health impact', as the activity is improving your health. Just be sure to stretch, and counter the muscle imbalances that the sport produces.
Many sports have similar results because they are unnatural. For example, snowboarders in big mountain areas end up with a unnaturally strong/tight oblique muscle on one side and one stronger leg. Surfers likely don't have this issue because the majority of their exertion occurs during the paddling phase and the length of time actually spent riding the wave is quite short.
