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Optimise Cassandra Query for faster result


By : David Craddock
Date : September 16 2020, 11:00 AM
it fixes the issue Your DB structure is most likely wrong when you have to use ALLOW FILTERING.
In cassandra it is not possible to use ranges queries on partition keys. What you need to do is modify your table structure to have a partition key which clusters your data (for example by date) and clustering keys start_range , end_range.
code :


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Optimise linq to sql query with subselect to get latest result


By : user2582203
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further var questionIDs assignment may be removed - you already filter QuizID and UserName in a second one.
Second query may be rewritten using groups so that whole function becomes one LINQ:
code :
public List<QuestionResult> GetLatestResult(Guid QuizID, string UserName) {
    return (
           from q in db.QuizResults
           where q.QuizId == QuizID && q.UserName == UserName
           group q by q.QuestionId into grouped
           select new QuestionResult {
               QuestionId = grouped.Key,
               AnswerId = grouped.OrderByDescending(q => q.CompletionDate).First().AnswerId
           };
       ).ToList();
}

how to optimise this MYSQL query to run faster


By : amirul saffuan
Date : March 29 2020, 07:55 AM
this will help I have two tables , I'd suggest using an explicit join instead of a subquery:
code :
SELECT 
 count(*) 
FROM
  responses res
INNER JOIN
  requests req
ON
  req.request_id=res.request_id
WHERE 
  req.user_id='$User_id'
  and res.status='U';

Why does MySQL not optimise this simple query and provide the result from cache?


By : christian james
Date : March 29 2020, 07:55 AM
this one helps. This behavior is documented in the manual.
Quoting the manual:

Optimise MySQL query, which uses sub-query; MariaDB much faster


By : Aalia Singh
Date : March 29 2020, 07:55 AM
To fix this issue You should move the ud.id=uc.users_details_id AND uc.platform_id = 1 AND ud.id=6 from WHERE to INNER JOIN
TO let it work properly add INDEX for uc.users_details_id ud.id is primary key so it's already indexed.

Can I optimise this further so that it runs faster?


By : Maxim Mashkov
Date : March 29 2020, 07:55 AM
wish of those help As you can see in the following pprof output, I have these nested for loops which take most of the time of my program. Source is in golang but code is explained below: ,
Can I optimise this further so that it runs faster?
code :
BenchmarkPeterSO-4   30    44089894 ns/op    5776666 B/op      31 allocs/op
BenchmarkIvan-4      10   152300554 ns/op   26023924 B/op    6022 allocs/op
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