Thanks Baptiste for the suggestion.

This limits large variables and avoids non-utf-8 in the TECHNICAL_500 output.

Thanks jonash for the initial patch; refs #20133.

Thanks giulettamasina for the report and Tim Graham for the review.

Also never create deferred model when no attrs are deferred.

Thanks to Tomin1 for the report.

SQLite doesn't work with more than 1000 parameters in a single query.
The deletion code could generate queries that try to get related
objects for more than 1000 objects thus breaking the limit. Django now
splits the related object fetching into batches with at most 1000
parameters.

The tests and patch include some work done by Trac alias NiGhTTraX in
ticket #21205.

Small modifications done by committer.

A regression caused queries to produce incorrect results for cases where
extra(select) is excluded by values() but included by extra(order_by)

The regression was caused by 2f35c6f1.

This fixes a regression introduced by 9012a9e2.

Thanks Claude Paroz for assistance with debugging the tests.

Thanks bendavis78 for the report.

Forwardport of 29585e9b from stable/1.7.x