CODEWITHSUNDEEP
google-app-enginegodata-modelinggoogle-cloud-datastore
Dustin Oprea
Dustin Oprea

Reputation: 10236

AppEngine/Datastore: Best way to retrieve since ancestor query returns everything recursively

When I do a get() with an ancestor constraint, it seems like I get all entities for that ancestor key and all ancestors that it is parent to.

In this case, I am using ancestral relationships to represent a homogenous tree (all nodes represented by the same kind; every level is immediately consistent). All of the IDs I am using are globally unique and I have the parent-ID written on each entity (in addition to it being in the ancestor path).

Since the by-ancestor retrieval returns too much data (all levels at and below rather than just the immediate level; The documentation doesn't mention this and a couple of others eccentricities), I'll need to add a filter to make sure I just get back the current level.

So, the question is whether there's a difference in efficiency to do a ancestor().filter() versus just filter() since these both produce the same results for me.

Thanks.

Upvotes: 4

Views: 215

Answers (1)

Dan McGrath
Dan McGrath

Reputation: 42018

Just filter() is eventually consistent, whereas ancestor().filter() is strongly consistent.

As you mentioned, you'll need to filter by an indexed a property to just get a particular level of the tree back.

Upvotes: 4

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