enable_eagerloads(False) automatically for .subquery(), .exists()

[sqlalchemy-bot]

Migrated issue, originally created by Michael Bayer (@zzzeek)

calling .exists() on an entity that has a subqueryload set up raises an error in 1.1 due to the internals not handling it correctly. There should be no reason eagerloads are called upon at all for an exists() and probably for .subquery() in general.

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

Disable eager loads for exists()

The :meth:.Query.exists method will now disable eager loaders for when
the query is rendered. Previously, joined-eager load joins would be rendered
unnecessarily as well as subquery eager load queries would be needlessly
generated. The new behavior matches that of the :meth:.Query.subquery
method.

Fixes: #4032
Change-Id: Iacafc76aa9ae0b71928037fa9637e85ad434ee3a

→ 1cbaff6

[sqlalchemy-bot]

Changes by Michael Bayer (@zzzeek):

• changed status to closed