Hi all, feel free to suggest moving this topic, I posted this once before in Assignment forum ( https://moodle.org/mod/forum/discuss.php?d=359553 )but did not get any answers.
We are having performance issues with group assignments grading, view all submissions - view. With normal assignments
the loading times for the view all submissions is few seconds, with group assignments this pumps up to 20 to seconds. We
looked into this and it seems that the view uses a query that takes 682ms to plan and 0.351ms to execute in PostgreSql, but it
runs the query 30 times to create the view -> 30 X 0.6seconds = 18seconds. This seems little excessive.
We do realize that part of the problem is the amount of groups & group members in our system (we generate them automatically for all
courses that have groupings in SMS) :
avle=# select count(*) from mdl_groups;
count
-------
30662
(1 row)
avle=# select count(*) from mdl_groups_members;
count
--------
302825
(1 row)
but this behavior is making the view all - view unusable.
I am attaching the Explain Analyze Query into this message.
Our environment is load-balanced 6 nodes (VM) with hardware DB (PostgreSql 9.4), yes it's a large installation... Any ideas how to proceed?
As you have put such a lot of effort into analyzing the problem I think you have answered your own question in many ways.
The next step is to raise this as a bug in tracker.moodle.org with all your information.