Index Question

[Joshua Smith]

I just wrote a new app and it has an entity that I use to show a leader board:

class CountModel(db.Model):
count = db.IntegerProperty(default=0)
trend = db.FloatProperty(default=0.0)

I get the list of these using a simple query:

if self.request.get("mode") == "trend":
counts = CountModel.gql("ORDER BY trend DESC").fetch(20)
else:
counts = CountModel.gql("ORDER BY count DESC").fetch(20)

I ran this in my dev environment and then checked index.yaml to make sure it made the indexes. It didn’t.

So I pushed it to production, fully expecting to see an error when I ran the query because I didn’t have this index defined. No error.

It works perfectly.

I also have this query in a cron job, and it works fine without the index, too:

for c in CountModel.gql("WHERE trend > 1"):

Has something changed? It used to be that to do an ordered query, or an inequality query, you had to have an index.

-Joshua

[Alex Martelli]

You still do, but single-property indices are generated automatically. That's documented at https://cloud.google.com/appengine/docs/python/datastore/indexes : "App Engine predefines a simple index on each property of an entity. An App Engine application can define further custom indexes".

and later in the same page, to clarify:

The Datastore builds automatic indexes for queries of the following forms:

Kindless queries using only ancestor and key filters

Queries using only ancestor and equality filters

Queries using only inequality filters (which are limited to a single property) 

etc. Your use case falls within the third one of these.

Alex

-Joshua

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[Joshua Smith]

Sweet! Thank you. I’ve been on GAE since the beginning, and I guess you added that at some point after I stopped reading the documentation ;)

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