When I tried to use an Artefact (Files, Images and Video) within a special Group - in my case it case I tried to use Image - I get that error message in debugger:
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Failed to get a recordset: mysql error: [1104: The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET SQL_MAX_JOIN_SIZE=# if the SELECT is okay] in EXECUTE(" SELECT a.id, a.artefacttype, a.mtime, f.size, a.title, a.description, a.locked, a.allowcomments, u.profileicon AS defaultprofileicon, COUNT(DISTINCT c.id) AS childcount, COUNT (DISTINCT aa.artefact) AS attachcount, COUNT(DISTINCT va.view) AS viewcount, COUNT(DISTINCT api.id) AS profileiconcount, r.can_edit, r.can_view, r.can_republish, a.author FROM "ep_artefact" a LEFT OUTER JOIN "ep_artefact_file_files" f ON f.artefact = a.id LEFT OUTER JOIN "ep_artefact" c ON c.parent = a.id LEFT OUTER JOIN "ep_artefact" api ON api.parent = a.id AND api.artefacttype = 'profileicon' LEFT OUTER JOIN "ep_view_artefact" va ON va.artefact = a.id LEFT OUTER JOIN "ep_artefact_attachment" aa ON aa.attachment = a.id LEFT OUTER JOIN "ep_usr" u ON a.id = u.profileicon AND a.owner = u.id LEFT OUTER JOIN ( SELECT ar.artefact, ar.can_edit, ar.can_view, ar.can_republish FROM "ep_artefact_access_role" ar INNER JOIN "ep_group_member" gm ON ar.role = gm.role WHERE gm.group = '1' AND gm.member = '2' ) r ON r.artefact = a.id WHERE a.artefacttype IN ('image','profileicon','folder') AND a.group = '1' AND a.owner IS NULL AND (r.can_view = 1 OR a.author = '2') AND a.parent IS NULL GROUP BY a.id, a.artefacttype, a.mtime, f.size, a.title, a.description, a.locked, a.allowcomments, u.profileicon, r.can_edit, r.can_view, r.can_republish, a.author") Command was: SELECT a.id, a.artefacttype, a.mtime, f.size, a.title, a.description, a.locked, a.allowcomments, u.profileicon AS defaultprofileicon, COUNT(DISTINCT c.id) AS childcount, COUNT (DISTINCT aa.artefact) AS attachcount, COUNT(DISTINCT va.view) AS viewcount, COUNT(DISTINCT api.id) AS profileiconcount, r.can_edit, r.can_view, r.can_republish, a.author FROM "ep_artefact" a LEFT OUTER JOIN "ep_artefact_file_files" f ON f.artefact = a.id LEFT OUTER JOIN "ep_artefact" c ON c.parent = a.id LEFT OUTER JOIN "ep_artefact" api ON api.parent = a.id AND api.artefacttype = 'profileicon' LEFT OUTER JOIN "ep_view_artefact" va ON va.artefact = a.id LEFT OUTER JOIN "ep_artefact_attachment" aa ON aa.attachment = a.id LEFT OUTER JOIN "ep_usr" u ON a.id = u.profileicon AND a.owner = u.id LEFT OUTER JOIN ( SELECT ar.artefact, ar.can_edit, ar.can_view, ar.can_republish FROM "ep_artefact_access_role" ar INNER JOIN "ep_group_member" gm ON ar.role = gm.role WHERE gm.group = ? AND gm.member = ? ) r ON r.artefact = a.id WHERE a.artefacttype IN ('image','profileicon','folder') AND a.group = ? AND a.owner IS NULL AND (r.can_view = 1 OR a.author = ?) AND a.parent IS NULL GROUP BY a.id, a.artefacttype, a.mtime, f.size, a.title, a.description, a.locked, a.allowcomments, u.profileicon, r.can_edit, r.can_view, r.can_republish, a.author and values was (1,2,1,2)
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When trying to open the Files Folder at the Group Site the following error message is printed
"A nonrecoverable error occured. This probably means you have encountered a bug in the system"
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I checked other groups. There all artefacts work. So it seems to be a special problem connected to that group. This is the main group where my students get their Inputs and works.
I tried to figure out that error statement. But I am no SQL expert and so I hope someone can give me help.
A more long term solution would be to reduce the number of joins made.
Solution would be to add SET SQL_BIG_SELECTS=1
This can be done in lib/dml.php round line 1478 (master)