I think if you give your func.xpath a datatype of pg.ARRAY(of whatever) you’ll get it:
func.xpath(…, type_=postgresql.ARRAY)[1]
>>> from sqlalchemy import func, String
>>> from sqlalchemy.dialects import postgresql
>>> print func.xpath('something', 'somethingelse',
>>> type_=postgresql.ARRAY(String()))[1].compile(dialect=postgresql.dialect())
xpath(%(xpath_1)s, %(xpath_2)s)[%(xpath_3)s]
>>>
On Dec 5, 2013, at 3:33 PM, Christian Lang <christian.a.l...@gmail.com> wrote:
> Hi,
>
> I'm trying to create the following index (on PostgreSQL) with SQLAlchemy 0.8:
>
> CREATE INDEX doc_idx ON xmltab (CAST((xpath('//@bla', doc))[1] AS TEXT));
>
> (where doc is a column of type XML)
>
> I got this far:
>
> Index("doc_idx", cast((func.xpath('//@bla', xmlTable.c.doc))[1], TEXT))
>
> but get the error:
> Traceback (most recent call last):
> File "xmltests.py", line 146, in <module>
> idx = Index("doc_idx", cast((func.xpath('//@bla', xmlTable.c.doc))[1],
> TEXT))
> File "build/bdist.linux-x86_64/egg/sqlalchemy/sql/operators.py", line 320,
> in __getitem__
> File "build/bdist.linux-x86_64/egg/sqlalchemy/sql/expression.py", line
> 2311, in operate
> File "build/bdist.linux-x86_64/egg/sqlalchemy/sql/operators.py", line 320,
> in __getitem__
> File "build/bdist.linux-x86_64/egg/sqlalchemy/sql/expression.py", line
> 1994, in operate
> File "build/bdist.linux-x86_64/egg/sqlalchemy/sql/expression.py", line
> 2148, in _unsupported_impl
> NotImplementedError: Operator 'getitem' is not supported on this expression
>
> It seems getitem should be allowed since the xpath expression returns an
> array of nodes (and it is fine in PostgreSQL).
> Any idea what I am doing wrong and how to fix it?
>
> Thanks,
> Christian
>
>
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