Optimize type filters

Requires !1304 (merged) and !1305 (merged), closes #699 (closed)

Note that while using type_id did give a performance boost when filtering by a single type, using type__in for folder=True or False did not bring any significant change, because Postgres just deduces that the subquery can be turned back into an inner join; it changes nothing to the query plan.

changed the description

added 11 commits

• 3957dc81...8ce7ccde - 5 commits from branch master
• fb18bf98 - Use the serializer context to get an element's corpus
• 3c728bd0 - Update for assertExactQueries
• 6e8e1d75 - Fetch the ElementType before filtering
• 08a32940 - Prefetch type
• 49ae13b8 - Cleaner filter handling
• f054e330 - type__in is not really performant

Compare with previous version

added 10 commits

• f054e330...6f932ee3 - 4 commits from branch master
• 09fb5992 - Use the serializer context to get an element's corpus
• 78fb256a - Update for assertExactQueries
• 729fe1e6 - Fetch the ElementType before filtering
• 7dc65365 - Prefetch type
• 71270abd - Cleaner filter handling
• 54946467 - type__in is not really performant

Compare with previous version

changed the description

added 2 commits

• d96eb5f6 - Fix all assertNumQueries
• e1fcb870 - First attempt at prefetch testing stuff

Compare with previous version

added 29 commits

• e1fcb870...85f21724 - 20 commits from branch master
• 90bf0e72 - Use the serializer context to get an element's corpus
• 4b47847a - Update for assertExactQueries
• 0dd5afa1 - Fetch the ElementType before filtering
• 9bf39c6e - Prefetch type
• 4740480f - Cleaner filter handling
• 743b8830 - type__in is not really performant
• b0bfc39b - Fix all assertNumQueries
• 2f95e9fa - First attempt at prefetch testing stuff
• 18db638e - Remove the prefetches from list_elements.sql entirely

Compare with previous version

marked this merge request as ready

requested review from @babadie

mentioned in issue #714

added 11 commits

• 18db638e...9392dd5b - 4 commits from branch master
• fc51658e - Fetch the ElementType before filtering
• 32acbdd9 - Prefetch type
• e00e331c - Cleaner filter handling
• bb18cb26 - type__in is not really performant
• 50c4c015 - Fix all assertNumQueries
• c509d8b9 - First attempt at prefetch testing stuff
• 8fb347bb - Remove the prefetches from list_elements.sql entirely

Compare with previous version

added 10 commits

• 8fb347bb...08fbf155 - 3 commits from branch master
• e90bd391 - Fetch the ElementType before filtering
• b83f7e2e - Prefetch type
• a1a69d13 - Cleaner filter handling
• ddb3f1c0 - type__in is not really performant
• 9bcfd430 - Fix all assertNumQueries
• 401b4dc2 - First attempt at prefetch testing stuff
• f9bf5231 - Remove the prefetches from list_elements.sql entirely

Compare with previous version

merged

mentioned in commit 9aa0ab14