Listing images which have tens of tags is too slow

[jaeswith]

Our client application retrieves all the images we have. The images have tens of tags with it. When asking these images with "limit=1000", it took 10+ seconds in my environment that uses 'mariadb'.

The API query we currently use:
`GET /v2/images?limit=1001&visibility=public`

We have about 200+ public images and half of them have more then 30 tags.

AFAIK, the main reason for this seems to be SQLalchemy and its generated queries, which use several 'left outer join'; images, image_properties, image_locations, and image_tags tables are joined. With 'limit=1000', this produces tremendous numbers of rows to be scanned.