Just a conclusion to this thread, I've been using the given snippet
with a minor modification with great success. The modification was
that single quotation marks had to be added around datetime.
class PGDateTime(TypeDecorator):
impl = DateTime
def literal_processor(self, dialect):
return lambda value: "'" + str(value) + "'"
If this could be implemented to be recognised automatically it'd very
valuable for a lot of users! But for me personally, I'm very happy
with the snippet.
On Wed, 30 Jan 2019 at 22:09, Mike Bayer <mike...@zzzcomputing.com> wrote:
>
> note someone was wroking on adding literal date rendering for Postgresql at:
>
> https://gerrit.sqlalchemy.org/#/c/sqlalchemy/sqlalchemy/+/18/
>
> but this review has fallen out of work. If you'd like to submit a
> complete feature request we can try to revive the work here.
>
> On Fri, Jan 25, 2019 at 7:58 PM Mike Bayer <mike...@zzzcomputing.com> wrote:
> >
> > On Fri, Jan 25, 2019 at 6:37 PM Zsolt Ero <zsolt....@gmail.com> wrote:
> > >
> > > I understand. I define my tables like
> > >
> > > Table('tablename', metadata, Column('time', DateTime(timezone=True),
> > > nullable=False))
> > >
> > > Can I simply replace DateTime with SDateTime and use timezone=True, or
> > > I'd need to add some initializer args for timezone?
> >
> > you should be able to do that, sure. TypeDecorator sends the
> > constructor arguments through to impl.
> >
> >
> > >
> > > Zsolt
> > >
> > > On Fri, 25 Jan 2019 at 03:58, Mike Bayer <mike...@zzzcomputing.com> wrote:
> > > >
> > > > On Thu, Jan 24, 2019 at 9:07 PM Zsolt Ero <zsolt....@gmail.com> wrote:
> > > > >
> > > > > Do I understand it right that there is no approach which could print a
> > > > > query without the need to modify it, if it contains datetimes?
> > > > >
> > > > > If so, how can I turn a where statement into something which is
> > > > > printable using SDateTime?
> > > > >
> > > > > .where(trips.c.end_time >= datetime.datetime.now())
> > > >
> > > > where you define your Table and its column called end_time, don't use
> > > > DateTime, use your custom version of that type.
> > > >
> > > > if you are relying upon reflection, use a column_reflect event
> > > > (https://docs.sqlalchemy.org/en/latest/core/events.html?highlight=column_reflect#sqlalchemy.events.DDLEvents.column_reflect)
> > > > to replace occurrences of DateTime with the custom DateTime object.
> > > >
> > > >
> > > > SQLAlchemy can of course eventually support rendering datetimes as
> > > > literal strings but this becomes a slippery slope where it has to
> > > > support literal rendering for every possible type, and we're then in a
> > > > place where we are reimplementing what the DBAPI already does and I
> > > > don't like to be doing that. We likely could benefit from a hook
> > > > that works like @compiles here but that's not available at this
> > > > moment.
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > >
> > > > > Zsolt
> > > > >
> > > > > On Mon, 21 Jan 2019 at 19:22, Mike Bayer <mike...@zzzcomputing.com>
> > > > > wrote:
> > > > > >
> > > > > > On Mon, Jan 21, 2019 at 12:23 PM Zsolt Ero <zsolt....@gmail.com>
> > > > > > wrote:
> > > > > > >
> > > > > > > Thanks it works perfectly, even with datetimes!
> > > > > > >
> > > > > > > Can I do something similar to make
> > > > > > >
> > > > > > > stmt.compile(dialect=postgresql.dialect(),
> > > > > > > compile_kwargs={"literal_binds": True})
> > > > > > >
> > > > > > > compatible with datetime? Or maybe not this, but I'm looking for
> > > > > > > a way
> > > > > > > to print a statement which I could copy and paste into psql
> > > > > > > console.
> > > > > >
> > > > > > that's what literal_binds is for but it doesn't support formatting
> > > > > > every kind of type directly, so I assume you're getting an error
> > > > > > message, at the moment the literal_processor can't be injected so
> > > > > > you
> > > > > > have to use a new type:
> > > > > >
> > > > > > from sqlalchemy import *
> > > > > > from sqlalchemy.dialects import postgresql
> > > > > > from sqlalchemy.ext.compiler import compiles
> > > > > > import datetime
> > > > > >
> > > > > >
> > > > > > class SDateTime(TypeDecorator):
> > > > > > impl = DateTime
> > > > > >
> > > > > > def literal_processor(self, dialect):
> > > > > > return lambda value: str(value)
> > > > > >
> > > > > >
> > > > > > print(
> > > > > > select([column("q", SDateTime) ==
> > > > > > datetime.datetime.now()]).compile(
> > > > > > dialect=postgresql.dialect(),
> > > > > > compile_kwargs=dict(literal_binds=True)
> > > > > > )
> > > > > > )
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > >
> > > > > > > Zsolt
> > > > > > >
> > > > > > > --
> > > > > > > SQLAlchemy -
> > > > > > > The Python SQL Toolkit and Object Relational Mapper
> > > > > > >
> > > > > > > http://www.sqlalchemy.org/
> > > > > > >
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> > > > > The Python SQL Toolkit and Object Relational Mapper
> > > > >
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> > > > The Python SQL Toolkit and Object Relational Mapper
> > > >
> > > > http://www.sqlalchemy.org/
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> > > --
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> > > The Python SQL Toolkit and Object Relational Mapper
> > >
> > > http://www.sqlalchemy.org/
> > >
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> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> description.
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