The scorm_scoes_track table has an index on the "element" field that doesn't appear to be used at all - and is quite large in some of our larger sites.

For example - the query here:
https://wiki.postgresql.org/wiki/Index_Maintenance#Index_size.2Fusage_statistics

Returns results like:
Table size: 4604MB
Index size: 1705MB
number_of_scans: 0

We do have a couple of sites that have less than 10 scans on the index. But the impact of having to maintain this index, the lack of use (and the disk usage) suggests we should be deleting this index.

The longer-term plan is to address: MDL-46279 but in the short-term I think we should drop this index.