ExcludeConstraint fails to quote column names when necessary.

[Chris Withers]

Given this model:

class MyModel(Base):
    __tablename__ = 'my_model'
    id = Column(Integer, primary_key=True)
    period = Column(TSRANGE())
    group = Column(String)
    __table_args__ = [ExcludeConstraint(('period', '&&'), ('group', '='))]

create_all will barf with a syntax error at or near "group"

[Mike Bayer]

why string name? why not (also fixed the args format):

class MyModel(Base):
    __tablename__ = 'my_model'
    id = Column(Integer, primary_key=True)
    period = Column(TSRANGE())
    group = Column(String)

#    __table_args__ = (ExcludeConstraint(('period', '&&'), ('group', '=')), )

    __table_args__ = (ExcludeConstraint((period, '&&'), (group, '=')), )

if you put a string here I don't know that this is giving SQLAlchemy enough context to know this is a single column name that is quotable.

[Mike Bayer]

OK, it says in the docstring for elements, "column name", fine, let me confirm that

[Mike Bayer]

derp, nope, our docstring is wrong, that string can be any SQL expression:

"The EXCLUDE clause defines an exclusion constraint, which guarantees that if any two rows are compared on the specified column(s) or expression(s) using the specified operator(s),"

and this is accepted:

class MyModel(Base):
    __tablename__ = 'my_model'
    id = Column(Integer, primary_key=True)
    period = Column(TSRANGE())
    group = Column(String)

    __table_args__ = (ExcludeConstraint((period, '&&'), (func.lower(group), '=')), )

[Mike Bayer]

e.g.

CREATE TABLE my_model (
    id SERIAL NOT NULL, 
    period TSRANGE, 
    "group" VARCHAR, 
    PRIMARY KEY (id), 
    EXCLUDE USING gist (period WITH &&, lower("group") WITH =)
)

fails for me for "gist" reasons but not syntactically.

[Mike Bayer]

• document that "column" and "where" are arbitrary SQL expressions for ExcludeConstraint, if string is used then quoting must be applied manually. fixes #3899

Change-Id: I5885c90179e4056b84fc4776464bba7c8c70a80a

→ <<cset a24801ae8de4>>

[Mike Bayer]

• document that "column" and "where" are arbitrary SQL expressions for ExcludeConstraint, if string is used then quoting must be applied manually. fixes #3899

Change-Id: I5885c90179e4056b84fc4776464bba7c8c70a80a (cherry picked from commit a24801ae8de469f1e78bdb0c02b28de263c2310e)

→ <<cset 00f2e31f210e>>

[Mike Bayer]

see #3454 where we actually allowed non-col expressions to be supported.