> In pure sql we can do :
> "select min(abs(width-150)) from quote_pricelisttable where name_id =
> 1 and width >= 240-150 and width <=240+150;"
>
> How to make it work properly from django ORM?
Did you try playing with the extra() call I included in my
previous email? It should do what you describe, and doesn't
require a fixed window such as you describe not wanting.
While it does rely on using some SQL, it does so through the
Django ORM and it should be fairly portable SQL (the "Abs()"
function is usually the "Abs()" function on most SQL engines).
The code I included (minus any syntax errors) should have found
the items from the given table where they were the minimum
distance from the target value.
w = 240 # target width to find the closest...comes from user
results = PriceList.objects.extra(where=["""
Abs(app_pricelist.width - %s) = (
SELECT Min(Abs(pl.width - %s))
FROM app_pricelist pl
)
"""], params=[w, w])
The results are a Django ORM query object that can be further
filtered, sliced, sorted, and iterated over with no problems.
While it can be done in pure python/django rather than SQL, it
would require dragging the whole PriceList across the wire and
filtering locally--a much slower proposition than simply letting
the DB do the work for you and shipping you just the exact
results you want.
-tim
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