Comment 6 for bug 1758160

I have also been testing this patch and it works for me, too. I have seen an 80% drop in the time to age circulations and a 75% drop in the time to purge users on my test database with this index added.

Michele's comment raises a valid concern, but I think adding the index is better than nothing at this point. We can always revisit the performance of this later if something else comes up.

I have signed off and pushed this to master, rel_3_1, and rel_3_0 for posterity.