Op donderdag 19 oktober 2017 03:10:21 UTC+2 schreef Mike Bayer:
>
> On Wed, Oct 18, 2017 at 7:38 AM, Gijs Molenaar <[email protected]
> <javascript:>> wrote:
> > hi!
> >
> >
> > Not sure if this a bug or something I should in my SQLAlchemy dialect,
> but
> > currently
> >
> >
> > expr = (table.c.x + table.c.y).label('lx')
> > select([func.count(table.c.id), expr]).group_by(expr).order_by(expr)
> >
> > compiles to:
> >
> > SELECT count(some_table.id) AS count_1, some_table.x + some_table.y AS
> lx
> > \nFROM some_table GROUP BY some_table.x + some_table.y ORDER BY lx;
> >
> >
> > which works fine for for example sqlite, but MonetDB requires the use of
> the
> > lx label in the GROUP BY, which I think makes sense? Should this be
> > addressed on the SQLalchemy side or on the MonetDB dialect side?
>
> so this was overhauled in
>
> http://docs.sqlalchemy.org/en/latest/changelog/migration_09.html#label-constructs-can-now-render-as-their-name-alone-in-an-order-by
>
> where we changed ORDER BY to use the label name when the expression is
> passed.
>
> so the immediate answer would be to not actually order by the label().
>
I think i didn't formulate my e-mail correctly. The ORDER BY is not the
problem, it is the GROUP BY that requires a label. If the GROUP BY doesn't
use a label (just like ORDER BY), MonetDB doesn't want to eat the query.
> At the compiler level, this behavior can be disabled across the board like
> this:
>
> diff --git a/lib/sqlalchemy/dialects/sqlite/base.py
> b/lib/sqlalchemy/dialects/sqlite/base.py
> index d8ce7f394..389d9bb02 100644
> --- a/lib/sqlalchemy/dialects/sqlite/base.py
> +++ b/lib/sqlalchemy/dialects/sqlite/base.py
> @@ -800,6 +800,10 @@ class SQLiteCompiler(compiler.SQLCompiler):
> 'week': '%W',
> })
>
> + def visit_label(self, elem, **kw):
> + kw.pop('render_label_as_label', None)
> + return super(SQLiteCompiler, self).visit_label(elem, **kw)
> +
> def visit_now_func(self, fn, **kw):
> return "CURRENT_TIMESTAMP"
>
>
>
> however no dialect does that right now, you'd need to watch this
> behavior closely across SQLAlchemy releases to make sure it doesn't
> break, unless we make this behavior official.
>
>
>
>
> >
> >
> > related issue:
> >
> >
> > https://github.com/gijzelaerr/sqlalchemy-monetdb/issues/21
> >
> > greetings,
> >
> > - Gijs
> >
> > --
> > 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
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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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