[#MDL-15947] Moodle locks the mysql database after some student/guest insertion on courses which belong to a meta-course

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Key:	MDL-15947
Type:	Bug
Status:	Open
Priority:	Major
Assignee:	Eloy Lafuente (stronk7)
Reporter:	Nivaldo A. P. de Vasconcelos
Votes:	0
Watchers:	1

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Moodle

Moodle locks the mysql database after some student/guest insertion on courses which belong to a meta-course

Created: 05/Aug/08 07:06 PM Updated: 23/Oct/08 05:04 AM

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Component/s:

Database SQL/XMLDB, Performance

Affects Version/s:

1.9.2

Fix Version/s:

None

File Attachments:

None

Image Attachments:

1. htop.screen.jpg
(226 kB)

Environment:

2 server Linux ubuntu (kernel image 2.6.20-16-server) : application with 4 Xeon E5345 processors, RAM 5.8GB; database with 4 Xeon E5345 processors, RAM 4.0 GB.

Database:	MySQL
Participants:	D P, Dan Poltawski, Eloy Lafuente (stronk7) and Nivaldo A. P. de Vasconcelos
Security Level:	None
Affected Branches:	MOODLE_19_STABLE

Description

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The moodle locks after a few insertions of students / visitors in a course which is linked to a meta-course. One of the database server processor is fully occupied and no other request for database is treated. It is as if there was a LOCK command in the database without answer.

From mytop application, it's possible to see the following query:
SELECT COUNT(DISTINCT prs.userid) FROM (SELECT ra.userid, ra.roleid AS primary_roleid, ....

It's attached the screen from htop.

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Nivaldo A. P. de Vasconcelos made changes - 05/Aug/08 07:12 PM

Field	Original Value	New Value
Attachment		htop.screen.jpg [ 14764 ]
Description	The moodle locks after a few insertions of students / visitors in a course which is linked to a meta-course. One of the database server processor is fully occupied and no other request for database is treated. It is as if there was a LOCK command in the database without answer.	The moodle locks after a few insertions of students / visitors in a course which is linked to a meta-course. One of the database server processor is fully occupied and no other request for database is treated. It is as if there was a LOCK command in the database without answer. From mytop application, it's possible to see the following query: SELECT COUNT(DISTINCT prs.userid) FROM (SELECT ra.userid, ra.roleid AS primary_roleid, .... It's attached the screen from htop.

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Dan Poltawski added a comment - 06/Oct/08 10:57 PM

Hi Nivaldo, could you give any more details about the query in question?

Entry in slow query log or full details for the query?

I can't find the query you reffer to when searching the moodle codebase.

Dan Poltawski made changes - 06/Oct/08 10:57 PM

Component/s		Database SQL/XMLDB [ 10131 ]
Security	Serious security issue [ 10000 ]
Component/s		Performance [ 10221 ]
Component/s	Database Activity [ 10092 ]
Priority	Blocker [ 1 ]	Major [ 3 ]
Component/s	Administration [ 10050 ]

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D P added a comment - 22/Oct/08 09:48 PM

Maybe I can second that:

MDL-16955

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Nivaldo A. P. de Vasconcelos added a comment - 23/Oct/08 05:04 AM

Hi Dan,

I have no idea about that query. After turn off the statistics module the did not happens more.
That query seems built on processing. I will check where I found the code closest on moodle codebase and post here.

Best regards,
Nivaldo

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