Event $whatever is under room !wrong instead of !right

[turt2live]

Description

During an initial sync of my massive account, I saw this appearing as synapse was marking /sync requests as processed (25 minutes later).

2018-05-24 20:04:04,376 - synapse.rest.client.v2_alpha.sync - 348 - WARNING - GET-80775- Event '$15038575302050923rSTmh:matrix.org' is under room u'!cURbafjkfsMDVwdRDQ:matrix.org' instead of '!liSMaPmhIAVOyCHhdT:matrix.org'
2018-05-24 20:04:04,379 - synapse.rest.client.v2_alpha.sync - 348 - WARNING - GET-80775- Event '$15038575562051193NuSGj:matrix.org' is under room u'!cURbafjkfsMDVwdRDQ:matrix.org' instead of '!DgvjtOljKujDBrxyHk:matrix.org'
2018-05-24 20:04:04,382 - synapse.rest.client.v2_alpha.sync - 348 - WARNING - GET-80775- Event '$15018848482433138yGYPS:matrix.org' is under room u'!cURbafjkfsMDVwdRDQ:matrix.org' instead of '!ZjJkQNQAlmRlGyyPSZ:matrix.org'
2018-05-24 20:04:04,389 - synapse.rest.client.v2_alpha.sync - 348 - WARNING - GET-80775- Event '$15038574582050065gMgtB:matrix.org' is under room u'!cURbafjkfsMDVwdRDQ:matrix.org' instead of '!PJuJrAtZEvdTHLxoWr:matrix.org'

The interesting thing is it seems to be related to whatever the sync pulls up. For instance, an hour or two later I stopped getting the first 3 warnings and was only seeing the last one.

Steps to reproduce (maybe)

• Have a big account
• Try and do a fresh /sync over and over
• Wait for warnings

Version information

• Homeserver: t2l.io
• Version: 0.29.1
• Install method: pip
• Platform: Ubuntu 16.04 lxc container on an Ubuntu 16.04 host

[richvdh]

this was basically fixed by #6472 and #6524, although that doesn't necessarily prevent existing rooms from being messed up in the database.