21 březen 2013
Google App Engine is full of hidden traps. One of them is the need to restart long running queries when
the query expired causing following exception to be thrown:
The requested query has expired. Please restart it with the last cursor to read more results
In Gaelyk 2.0
you can now tell your query
to restart automatically if this happen. Restarting happen under the hood so you can use for loops flawlessly.
To enable automatic restarting of queries add restart automatically statement to your query dsl.
Currenty, you can only use this option on iterate method, because it doesn't make much sense with execute
method.
Simple restarting query
def comments = datastore.iterate {
from Comment
limit 50000
restart automatically
}
for(comment in comments){
// would throw exception randomly for long running queries
process comment
}
You can use restart automatically with select all and select keys query types. It also works with
coerced queries using as Type keyword e.g. form 'Comment' as Comment.