mike bayer <mike...@zzzcomputing.com> writes:
> However, we can improve upon the situation by adding a CAST, which seems to
> send psycopg2 a little more information:
>
> row = s.query(
> cast(
> func.array_agg(tuple_(A.x, A.y)), ARRAY(Unicode)
> )
> ).scalar()
> print row
For one new application I'm writing I chose the "new" asyncpg[1] driver.
The major problem I hit was related to this CASTing need ([2] and [3]): due to
the way asyncpg talks to the database, in some cases it cannot guess the right
format because on the PG side things may be ambiguous (e.g. when an operator
is overloaded and works on different types of data, like the @> operator I
used in [3]).
To solve that I wrote a very simple custom PGDialect+PGCompiler duo to handle
a new "paramstyle", basically translating the following SA construct::
oneyearago = date.today() - timedelta(days=365)
q = sa.select([users.c.id]) \
.where(users.c.name == 'test') \
.where(users.c.validity.contains(oneyearago))
into this SQL statement::
SELECT auth.users.id
FROM auth.users
WHERE auth.users.name = $1::VARCHAR(64) AND (auth.users.validity @> $2::DATE)
Since it eventually boils down to overriding a single "private" method
(_apply_numbered_params), I wonder if it would be a welcome addition to
standard SA, maybe allowing to set "paramstyle" to an user's arbitrary
callable.
What do you think?
Thank you,
ciao, lele.
[1] https://github.com/MagicStack/asyncpg
[2] https://github.com/CanopyTax/asyncpgsa/issues/12
[3] https://github.com/MagicStack/asyncpg/issues/32
--
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
l...@metapensiero.it | -- Fortunato Depero, 1929.
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