CODEWITHSUNDEEP
google-app-enginegoogle-cloud-datastore
Okku
Okku

Reputation: 1167

App engine datastore inconsistent?

This is so weird...

First of all this query works in the datastore viewer, ie. it returns the correct row.

SELECT * FROM Level where short_id = 'Ec71eN'

But if I run this

Level.all().filter("short_id = ", 'Ec71eN').get()

it returns None, if I run this:

db.GqlQuery("SELECT * FROM Level where short_id = '%s'" % 'Ec71eN').get()

it also returns None. If I run this:

level = Level.get_by_id(189009)

it returns the correct row (189009 is the id for the correct row)

Puzzling? What can be wrong here? I have never seen anything like this before, it has worked correctly for at least a couple of weeks in production... I think I have at least two cases now where it dosent work starting today.

UPDATE: This can not be a eventually consistent problem since the row was 7 hours old when I tried the above. I had two rows with same symptoms, strangely booth generated by the same users. They where booth "fixed" after I did a manual fecth of their ids by uploading special case code like: 

if short_id==CASE_1_SHORT_ID: 
     level = Level.get_by_id(CASE_1_ID)

After that the query worked as usual.

Upvotes: 1

Views: 349

Answers (2)

flynn
flynn

Reputation: 1584

Given that it was created 7 hours ago, the 'eventual consistency' generally should take seconds to minutes. If eventual consistency IS the problem, run the same query method a bunch of times and see if returns the same result. If it continuously returns the same result with the same method, then it is more than likely not an eventual consistency problem. You should switch to the NDB API for querying data as well - it's 1000 times better and Guido worked on it - so you know it's good. Does NDB show the same inconsistency?

Upvotes: 1

dragonx
dragonx

Reputation: 15143

Are you using the HRD? Nothing's wrong. You know it's supposed to be eventually consistent right?

Query operations are eventually consistent. Get-by-id operations are fully consistent.

What you describe is correct datastore behavior. It's a bit odd that the datastore viewer operation returns the correct result, but it might have hit a separate tablet on the datastore operation.

Upvotes: 4

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