I'm trying to get paginated results in cassandra using springboot, but I'm not getting desired results. Here is my code.
Slice<User> usersByNameSlice =
userRepository.findAll(CassandraPageRequest.first(10));
while (usersByNameSlice .hasNext()) {
//.. process
usersByNameSlice = userRepository.findAll(usersByNameSlice.nextPageable());
}
I have around 35 users. This while loop works 3 times covering 30 users, but it comes out of the while loop after 30. How to solve this problem?
I think that you need to change the condition of the while loop to usersByNameSlice.hasContent() to check if there is content in the slice at all.
(Or maybe to combine it with check isPaged() even - because nextPageable on the last page will return unpaged state).
Related
Paginate not working for specific model. with all Models, paginate is working fine except one specific model. Also tried with query builder.
$doubts = DB::table('users')->paginate(10);
dd($doubts->count());
//output: 10
$doubts = DB::table('doubts')->paginate();
dd($doubts->count());
//output: 0
$doubts = DB::table('doubts')->get();
dd($doubts->count());
//output: 8
Don't know what am I missing here. Please help.
Maybe I think you have to put
How many results you want to show per page
So if you want 8
Then I think it should be something like this
$doubts = DB::table('doubts')->paginate(8);
dd($doubts->count());
And if you are using pages Number under your data then you might need the query builder.
You should pass number argument inside paginate function.
Look at laravel pagination documentation
And make sure that DB::table('doubts')
Is returning collection
I thing you must add parameter in paginate(), to show how much data that show per page. You can read documentation in : https://laravel.com/docs/9.x/pagination#paginating-query-builder-results
https://laravel.com/docs/9.x/pagination#cursor-pagination
because you are not add parameter in paginate, it means not data that show every page.
$doubts = DB::table('doubts')->paginate(10);
I am loading data from excel. In foreach I am checking for each record if it does exist in database:
$recordExists = $this->checkIfExists($record);
function checkIfExists($record) {
$foundRecord = $this->repository->newQuery()
->where(..., $record[...])
->where(..., $record[...])
...
->get();
}
When the excel contains up to 1000 values which is relatively small piece of data - the code runs around 2 minutes. I am guessing this is very inefficient way to do it.
I was thinking of passing the array of loaded data to the method checkIfExists but then I could not query on the data.
What would be a way to proceed?
You can use laravel queue if you want to do a lot of work within a very short time. Your code will run on backend. Client can not recognize the process. just show a message to client that this process is under queue. Thats it
You can check the Official Documentation From Below Url
https://laravel.com/docs/5.8/queues
If you passes all the data from the database to the function (so no more queries to the database), you can use laravel collections functions to filter.
On of them is where => https://laravel.com/docs/5.8/collections#method-where
function checkIfExists($record, Collection $fetchedDataFromDatabase) {
// laravel collectons 'where' function
$foundRecord = $fetchedDataFromDatabase
->where(..., $record[...])
->where(..., $record[...]);
}
other helpful functions.
filter
contains
Is it acceptable to perform multiple increment operations on different fields of the same object on Parse Server ?
e.g., in Cloud Code :
node.increment('totalExpense', cost);
node.increment('totalLabourCost', cost);
node.increment('totalHours', hours);
return node.save(null,{useMasterKey: true});
seems like mongodb supports it, based on this answer, but does Parse ?
Yes. One thing you can't do is both add and remove something from the same array within the same save. You can only do one of those operations. But, incrementing separate keys shouldn't be a problem. Incrementing a single key multiple times might do something weird but I haven't tried it.
FYI you can also use the .increment method on a key for a shell object. I.e., this works:
var node = new Parse.Object.("Node");
node.id = request.params.nodeId;
node.increment("myKey", value);
return node.save(null, {useMasterKey:true});
Even though we didn't fetch the data, we don't need to know the previous value in order to increment it on the database. Note that you don't have the data so can't access any other necessary data here.
I'm using Grails with an Oracle database. Most of the data in my application is part of a hierarchy that goes something like this (each item containing the following one):
Direction
Group
Building site
Contract
Inspection
Non-conformity
Data visible to a user is filtered according to his accesses which can be at the Direction, Group or Building Site level depending on user role.
We easily accomplished this by creating a listWithSecurity method for the BuildingSite domain class which we use instead of list across most of the system. We created another listWithSecurity method for Contract. It basically does a Contract.findAllByContractIn(BuildingSite.listWithSecurity). And so on with the other classes. This has the advantage of keeping all the actual access logic in BuildingSite.listWithsecurity.
The problem came when we started getting real data in the system. We quickly hit the "ora-01795 maximum number of expressions in a list is 1000" error. Fair enough, passing a list of over 1000 literals is not the most efficient thing to do so I tried other ways even though it meant I would have to deport the security logic to each controller.
The obvious way seemed to use a criteria such as this (I only put the Direction level access here for simplicity):
def c = NonConformity.createCriteria()
def listToReturn = c.list(max:params.max, offset: params.offset?.toInteger() ?: 0)
{
inspection {
contract {
buildingSite {
group {
'in'("direction",listOfOneOrTwoDirections)
}
}
}
}
}
I was expecting Grails to generate a single query with joins that would avoid the ora-01795 error but it seems to be calling a separate query for each level and passing the result back to Oracle as literal in an 'in' to query the other level. In other words, it does exactly what I was doing so I get the same error.
Actually, it might be optimising a bit. It seems to be solving the problem but only for one level. In the previous example, I wouldn't get an error for 1001 inspections but I would get it for 1001 contracts or building sites.
I also tried to do basically the same thing with findAll and a single HQL where statement to which I passed a single direction to get the nonConformities in one query. Same thing. It solves the first levels but I get the same error for other levels.
I did manage to patch it by splitting my 'in' criteria into many 'in' inside an 'or' so no single list of literals is more than 1000 long but that's profoundly ugly code. A single findAllBy[…]In becomes over 10 lines of code. And in the long run, it will probably cause performance problems since we're stuck doing queries with a very large amount of parameters.
Has anyone encountered and solved this problem in a more elegant and efficient way?
This won't win any efficiency awards but I thought I'd post it as an option if you just plainly need to query a list of more than 1000 items none of the more efficient options are available/appropriate. (This stackoverflow question is at the top of Google search results for "grails oracle 1000")
In a grails criteria you can make use of Groovy's collate() method to break up your list...
Instead of this:
def result = MyDomain.createCriteria().list {
'in'('id', idList)
}
...which throws this exception:
could not execute query
org.hibernate.exception.SQLGrammarException: could not execute query
at grails.orm.HibernateCriteriaBuilder.invokeMethod(HibernateCriteriaBuilder.java:1616)
at TempIntegrationSpec.oracle 1000 expression max in a list(TempIntegrationSpec.groovy:21)
Caused by: java.sql.SQLSyntaxErrorException: ORA-01795: maximum number of expressions in a list is 1000
at oracle.jdbc.driver.T4CTTIoer.processError(T4CTTIoer.java:440)
You'll end up with something like this:
def result = MyDomain.createCriteria().list {
or { idList.collate(1000).each { 'in'('id', it) } }
}
It's unfortunate that Hibernate or Grails doesn't do this for you behind the scenes when you try to do an inList of > 1000 items and you're using an Oracle dialect.
I agree with the many discussions on this topic of refactoring your design to not end up with 1000+ item lists but regardless, the above code will do the job.
Along the same lines as Juergen's comment, I've approached a similar problem by creating a DB view that flattens out user/role access rules at their most granular level (Building Site in your case?) At a minimum, this view might contain just two columns: a Building Site ID and a user/group name. So, in the case where a user has Direction-level access, he/she would have many rows in the security view - one row for each child Building Site of the Direction(s) that the user is permitted to access.
Then, it would be a matter of creating a read-only GORM class that maps to your security view, joining this to your other domain classes, and filtering using the view's user/role field. With any luck, you'll be able to do this entirely in GORM (a few tips here: http://grails.1312388.n4.nabble.com/Grails-Domain-Class-and-Database-View-td3681188.html)
You might, however, need to have some fun with Hibernate: http://grails.org/doc/latest/guide/hibernate.html
If I have multiple GeoCoordinateWatchers in a WP7 application, they seem to cause conflict with one another. I would assume that if I have a watcher setup like:
new GeoCoordinateWatcher(GeoPositionAccuracy.High) { MovementThreshold = 0 }
and another setup like:
That the value from the first should be extremely accurate whereas the second one should be used as a point of reference.
new GeoCoordinateWatcher(GeoPositionAccuracy.Default) { MovementThreshold = 1000 };
However, the second one causes the first coordinates to jump all over the place. If I comment out the second, the first works as expected. Any idea why?
Try setting the same accuracy and see if you get the same values.