* automatically does with_exclusive_scope
* if the scope has an order or group by, use an alternate
implementation so it's not broken
* alternate methods are cursors (postresql only) or temporary
tables. if a transaction is already open, or we're on a slave,
prefer a cursor (even over the normal method, since the query
might be slow even without an order or group by)
test plan:
* migrations should still work (especially data fixups)
* lots of account reports use find_each; make sure they still run
Change-Id: If876b7b3401e6cda1d41f1c94b93af4810b78cf4
Reviewed-on: https://gerrit.instructure.com/22364
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jon Jensen <jon@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
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