[Sqlalchemy-tickets] Issue #3174: support text() sent to indexes (zzzeek/sqlalchemy)

[Mike B. <iss...@bi...>]

New issue 3174: support text() sent to indexes
https://bitbucket.org/zzzeek/sqlalchemy/issue/3174/support-text-sent-to-indexes

Mike Bayer:

this works in general, but fails on at least the Postgresql dialect because it is linking each expression to a column.  See https://bitbucket.org/zzzeek/alembic/issue/222/support-functional-indexes-with for how alembic works around this.

```
#!python

from sqlalchemy import *
from sqlalchemy.schema import CreateIndex
from sqlalchemy.dialects import postgresql

m = MetaData()
t = Table('x', m)
idx = Index('foo', text("lower(c)"))
idx._set_parent(t)

print CreateIndex(idx).compile(dialect=postgresql.dialect())
```