On Feb 20, 3:13 pm, pedepy <paul.ro...@gmail.com> wrote:
> Hi .. I just stumbed upon a NeedIndexError. I understand why it
> happens, but I dont quite understand the 'motivations' behind it.
>
> If the development server can just generate indexes for queries as I
> make them, why would that not be possible for the deployed app? My app
> makes extensive use of Expando objects who's properties I cannot fully
> predict. As such, the combination of all possible queries is also
> almost possible to determine before hand.
The development server does not generate indexes, actually. Whenever
you do a query, it loops over every item in the datastore, filtering
for those that match your query. Obviously, this scales rather badly,
but on the plus side, dealing with a query that would otherwise use a
new index is trivial :)
Actually generating a new index requires sorting every item of the
model in question and building an index out of that. As Dan points
out, that can be a very expensive operation, and moreover ongoing
costs for inserts/updates should be a concern.
Since you've not given any details about /why/ you're using Expando
objects, all I can say is that you'll have to get clever with one or
two special properties to manufacture whatever queries you want.
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