问题
I understand that with parse there is a PFQuery limit where you can only retrieve 1000 objects at a time. I presume it doesn't, but does this also limit the number of whereKey comparisons that can be carried out. E.g.
var query = PFQuery(classname: "Photos")
query.whereKey("Name", equalTo: someString)
query.findObjectsInBackgroundWithBlock()
If there are more than 1000 objects in the class, will the whereKey comparison stop after it has compared 1000 objects, or is the issue with only actually retrieving more than 1000 objects?
The reason I presume there is not a limit on this, is that If you have more than 1000 users, there would be no straight forward way to do a standard user query.
回答1:
Using the whereKey parameters does not effect your fetch limits, in fact, it reduces them simply due to the fact of its purpose. The point of including keys is to narrow it down correct? You can even include multiple keys or whereKey statements in the same query. So by narrowing it down further your reduce the probable objects to be fetched. So in short, your presumption is correct.
Lets be clear firstly, whereKey isn't actually doing anything, its setting a filter [parameter] and applying it to your asynchronous calls for the given blocks to do something with those keys. The findObjects is what returns your limit that you now know is 1000. You can skip queries See Here which effectively means you can query for the first 1000 and skip those you've already queried once your ready to display further results [pagination]. So to answer your second question, whereKey parameter won't stop doing anything, because it kind of isn't anyways, nor will you stop retrieving objects, you just have to learn how to navigate around your first 1000 returned objects.
- There are numerous ways of querying users, it all depends on your apps direction and current set up. You have to think about Parse as a business and not a service, they make money off of API requests, so the more you do the better it is for them. I would suggest coming back to SO once you get to where you have an issue with this so someone can help you out, if you need it.
来源：https://stackoverflow.com/questions/27867638/parse-com-query-limit-effects-wherekey-limit