form of a some expressions when referring to the ``.c`` collection on a ``select()`` construct, but the ``str()`` form isn't available since the element relies on dialect-specific compilation constructs, notably the ``__getitem__()`` operator as used with a Postgresql ``ARRAY`` element. The fix also adds a new exception class :class:`.UnsupportedCompilationError` which is raised in those cases where a compiler is asked to compile something it doesn't know how to. [ticket:2780]
- add support for correlations to propagate all the way in; because correlations require context now, need to make sure a select enclosure of any level takes effect any number of levels deep. - fix what we said correlate_except() was supposed to do when we first released #2668 - "the FROM clause is left intact if the correlated SELECT is not used in the context of an enclosing SELECT..." - it was not considering the "existing_froms" collection at all, and prohibited additional FROMs from being placed in an any() or has(). - add test for multilevel any() - lots of docs, including glossary entries as we really need to define "WHERE clause", "columns clause" etc. so that we can explain correlation better - based on the insight that a SELECT can correlate anything that ultimately came from an enclosing SELECT that links to this one via WHERE/columns/HAVING/ORDER BY, have the compiler keep track of the FROM lists that correspond in this way, link it to the asfrom flag, so that we send to _get_display_froms() the exact list of candidate FROMs to correlate. no longer need any asfrom logic in the Select() itself - preserve 0.8.1's behavior for correlation when no correlate options are given, not to mention 0.7 and prior's behavior of not propagating implicit correlation more than one level.. this is to reduce surprises/hard-to-debug situations when a user isn't trying to correlate anything. Conflicts: doc/build/changelog/changelog_08.rst doc/build/changelog/changelog_09.rst lib/sqlalchemy/sql/compiler.py
foreign key paths to a table "B", to that table "B", would fail to produce the "ambiguous join condition" error that would be reported if you join table "A" directly to "B"; it would instead produce a join condition with multiple criteria. [ticket:2738] Conflicts: doc/build/changelog/changelog_09.rst
labeled columns when apply_labels() is used; this mode produces a SELECT where each column is labeled as in <tablename>_<columnname>, to remove column name collisions for a multiple table select. The fix is that if two labels collide when combined with the table name, i.e. "foo.bar_id" and "foo_bar.id", anonymous aliasing will be applied to one of the dupes. This allows the ORM to handle both columns independently; previously, 0.7 would in some cases silently emit a second SELECT for the column that was "duped", and in 0.8 an ambiguous column error would be emitted. The "keys" applied to the .c. collection of the select() will also be deduped, so that the "column being replaced" warning will no longer emit for any select() that specifies use_labels, though the dupe key will be given an anonymous label which isn't generally user-friendly. [ticket:2702]
could impact some usages of the new :func:`.orm.remote` and :func:`.orm.local` annotation functions, where annotations could be lost when the column were used in a subsequent expression. [ticket:2660]
so that they can be compared in ``__nonzero__`` prior to their self_group() step. [ticket:2621]
could be lost if the statement were used as a subquery inside of another statement, as well as other similar situations. Among other things, would cause typing information to be lost when the Oracle/mssql dialects would apply limit/offset wrappings. [ticket:2603]
used when producing a "proxy" of the column against a selectable. This probably didn't occur in 0.7 since 0.7 doesn't respect the ".key" in a wider range of scenarios. [ticket:2597]