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Message #15320
[Bug 1081947] Re: Use of CAST() causes extreme slowdown in large MySQL sites
>From what I've found during initial investigations is that in Mahara
v1.0 the artefact_access_role and artefact_access_usr tables did not
exist - they were added in version 1.1.
If one does a fresh install of Mahara using v1.1 or later they get those
two tables with the correct constraints/keys/foreign keys
However if they upgrade from version 1.0 they get those two tables
missing all of the constraints/keys/foreign keys.
I've upgraded all the way form 1.0 to 1.8 in mysql and the keys are
missing.
What is needed to start with is a patch to add the missing keys onto
sites that have been upgraded from Mahara v1.0
** Changed in: mahara
Assignee: (unassigned) => Robert Lyon (robertl-9)
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https://bugs.launchpad.net/bugs/1081947
Title:
Use of CAST() causes extreme slowdown in large MySQL sites
Status in Mahara ePortfolio:
Confirmed
Bug description:
Mahara version 1.5.2
Linux CentOS release 5.8
PHP Version 5.3.15
MySQL 5.0.77
When editing a page and trying to add a normal text box by dragging it
into the page, this loads for approx 2 minutes or more and then
eventually appears.
It happens with a journal too but all others are fine and are instant
as they should be.
I'm not getting any apache log errors for this nor general server
errors. The only thing I am able to see is the query that it hangs on
for this length of time.... it is the below...
I hope someone can help as obviously this is causing quite a lot of
issues for the users!! Anyone able to diagnose what is the issue here?
The thing is, there is another exact version of the Mahara site
alongside this one but just a blank version which runs perfectly fine
so this must be an issue within the database somewhere or the
maharadata.
Query below: this hangs for about 1 minute 45..
SELECT a.*, CAST(a.owner IS NOT NULL AND a.owner = '1739' AS UNSIGNED) AS editable FROM "artefact" a
LEFT OUTER JOIN "artefact_parent_cache" apc ON (a.id = apc.artefact AND a.institution = 'mahara' AND apc.parent = 371) WHERE (
a.owner = '1739'
OR a.id IN (
SELECT aar.artefact
FROM "group_member" m
JOIN "artefact" aa ON m.group = aa.group
JOIN "artefact_access_role" aar ON aar.role = m.role AND aar.artefact = aa.id
WHERE m.member = '1739' AND aar.can_republish = 1
)
OR a.id IN (SELECT artefact FROM "artefact_access_usr" WHERE usr = '1739' AND can_republish = 1)
OR a.institution IN ('test','mahara')
) AND artefacttype IN('blog')ORDER BY title ASC LIMIT 10 |
Then this one for the rest of the time until eventually the text box
or journal appears on the page:
SELECT COUNT(*) FROM "artefact" a
LEFT OUTER JOIN "artefact_parent_cache" apc ON (a.id = apc.artefact AND a.institution = 'mahara' AND apc.parent = 371) WHERE (
a.owner = '1739'
OR a.id IN (
SELECT aar.artefact
FROM "group_member" m
JOIN "artefact" aa ON m.group = aa.group
JOIN "artefact_access_role" aar ON aar.role = m.role AND aar.artefact = aa.id
WHERE m.member = '1739' AND aar.can_republish = 1
)
OR a.id IN (SELECT artefact FROM "artefact_access_usr" WHERE usr = '1739' AND can_republish = 1)
OR a.institution IN ('test','mahara')
) AND artefacttype IN('blogpost') |
Thank you for your help
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References