Обсуждение: ISQLQuote vs. str subclass

I have a custom subclass of str called LiteralValue, the purpose of
which is to represent a string which should be passed to Postgres
unmodified. Its getquoted() method simply returns itself. This type
worked as intended with psycopg2 up to version 2.2.x. However, versions
of psycopg2 2.3 and newer no longer call getquoted() on objects of type
LiteralValue. Is this an expected change in behavior?
--
Jonathan Ross Rogers

On Fri, Jul 31, 2015 at 3:57 PM, Jonathan Rogers
<jrogers@socialserve.com> wrote:
> I have a custom subclass of str called LiteralValue, the purpose of
> which is to represent a string which should be passed to Postgres
> unmodified. Its getquoted() method simply returns itself. This type
> worked as intended with psycopg2 up to version 2.2.x. However, versions
> of psycopg2 2.3 and newer no longer call getquoted() on objects of type
> LiteralValue. Is this an expected change in behavior?

I don't think so, not intentionally at least. If the class is
self-adapting, does it expose a __conform__() method? If it has an
associated wrapper is it registered?

http://initd.org/psycopg/docs/advanced.html#adapting-new-python-types-to-sql-syntax

If you post the implementation I can try and take a look.

-- Daniele

On 07/31/2015 12:08 PM, Daniele Varrazzo wrote:
> On Fri, Jul 31, 2015 at 3:57 PM, Jonathan Rogers
> <jrogers@socialserve.com> wrote:
>> I have a custom subclass of str called LiteralValue, the purpose of
>> which is to represent a string which should be passed to Postgres
>> unmodified. Its getquoted() method simply returns itself. This type
>> worked as intended with psycopg2 up to version 2.2.x. However, versions
>> of psycopg2 2.3 and newer no longer call getquoted() on objects of type
>> LiteralValue. Is this an expected change in behavior?
>
> I don't think so, not intentionally at least. If the class is
> self-adapting, does it expose a __conform__() method? If it has an
> associated wrapper is it registered?
>
> http://initd.org/psycopg/docs/advanced.html#adapting-new-python-types-to-sql-syntax
>
> If you post the implementation I can try and take a look.

Here's a sample script which demonstrates the difference in behavior.
Using psycopg2 2.2.1, it prints four lines of "select 5". Using psycopg2
2.3, the line using a LiteralValue is "select '5'".

--
Jonathan Ross Rogers