ExcludeConstraint breaks autogenerate

[sqlalchemy-bot]

Migrated issue, originally created by dataradiant (@dataradiant)

Using ExcludeConstraint() seems to break alembic's autogenerate.

I'm specifying the constraint in my __table_args__ as:
ExcludeConstraint(("destination_id", "="), ("route_id", "="), ("timerange","&&"), name="uq_msgtime", using="gist")

The error is ValueError: no dispatch function for object: ExcludeConstraint(). https://bitbucket.org/zzzeek/alembic/src/377198f274edad3220a9485c30827251f848fdac/alembic/util/langhelpers.py?at=master&fileviewer=file-view-default#langhelpers.py-300

It seems that the _registry attribute of the Dispatcher object doesn't contain the required tuple, specifically one that has any of the classes in the ExcludeConstraint mro.

[sqlalchemy-bot]

Changes by dataradiant (@dataradiant):

• edited description

[sqlalchemy-bot]

Changes by dataradiant (@dataradiant):

• edited description

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

so yes that should at the very least degrade gracefully as it does for other things that are non-detectable, then the PG impl can also deliver an implementation for this. that this blocks autogenerate makes it more urgent but I don't have time to get to it until next week, hope this is not blocking you.

[sqlalchemy-bot]

Changes by Michael Bayer (@zzzeek):

• set milestone to "fasttrack"

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

this is on render, not compare.

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

Add ExcludeConstraint support for Postgresql

Add full support for Postgresql add_exclude_constraint().
This opens up more of the operations API and serves as a
model for other dialect-specific constraints.

Additionally, gracefully degrade if a given constraint
class is not supported with a warning.

Fixes: #412
Change-Id: I0fb89c840518aaeae97929919356f944479bc756

→ 01db038

[sqlalchemy-bot]

Changes by Michael Bayer (@zzzeek):

• changed status to closed

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

Issue #386 was marked as a duplicate of this issue.