On Thu, Apr 19, 2018 at 9:52 AM, Антонио Антуан <a.ch....@gmail.com> wrote:
> So, anyway, I must implement BitAnd class? Or I can check if 'element.op ==
> &' inside compile function?
uh sure you can do that, it would be sqlalchemy.sql.operators.and_op
or something like that
>
> чт, 19 апр. 2018 г., 16:31 Mike Bayer <mike...@zzzcomputing.com>:
>>
>> On Thu, Apr 19, 2018 at 5:21 AM, Антонио Антуан <a.ch....@gmail.com>
>> wrote:
>> > Hi guys.
>> >
>> > Is there any mechanism in SQLAlchemy which allows to redefine operator
>> > compilation? I want to the same thing as already exists for functions.
>> > An example for functions:
>> >
>> >
>> > class IntDiv(GenericFunction):
>> > type = Integer
>> > package = 'adc_custom'
>> > name = 'div'
>> > identifier = 'div'
>> >
>> >
>> > @compiles(IntDiv)
>> > def visit_div_default(element, compiler, **kwargs):
>> > params = [compiler.process(c.self_group()) for c in
>> > element.clause_expr.element.get_children()]
>> > return '%s / %s' % (params[0], params[1])
>> >
>> >
>> > @compiles(IntDiv, 'clickhouse')
>> > def visit_div_ch(element, compiler, **kwargs):
>> > return 'intDiv(%s)' % compiler.process(element.clause_expr.element)
>> >
>> > What I want to do:
>> >
>> > class BitAdd(CustomOp):
>> > pass
>> >
>> > @compiles(BitAdd)
>> > def visit_bit_add_default(element, compiler, **kwargs):
>> > return '%s & %s' % (element.left, element.right)
>> >
>> >
>> > @compiles(IntDiv, 'clickhouse')
>> > def visit_bit_add_ch(element, compiler, **kwargs):
>> > return 'bitAnd(%s, %s)' % (element.left, element.right)
>> >
>> > Statement looks like that:
>> > some_col.op('&')(some_int_flag)
>> >
>> >
>> > I understand that I can define generic function and use it instead of
>> > `.op('&')`, but at first I want to find another way.
>>
>> So in this case you are looking to override the compilation for
>> BinaryElement in any case since you want to run a function around them
>> in one case, that is the whole left/operator/right object.
>>
>> from sqlalchemy.sql.expression import BinaryExpression
>> @compiles(BinaryExpression, "clickhouse")
>> def visit_binary(element, compiler, **kw):
>> if isinstance(element.operator, BitAdd):
>> return "bitAnd(%s, %s)" % (compiler.process(element.left,
>> **kw), compiler.process(element.right, **kw))
>> else:
>> return compiler.visit_binary(element, **kw)
>>
>> For the part where you want op('&') to be magic, it can't work that
>> way, though you can get at the '&' operator directly but you normally
>> need to use a subclass of Integer:
>>
>>
>> http://docs.sqlalchemy.org/en/latest/core/custom_types.html#redefining-and-creating-new-operators
>>
>> so here you'd be saying:
>>
>> from sqlalchemy import Integer
>>
>> class MyInt(Integer):
>> class comparator_factory(Integer.Comparator):
>> def __and__(self, other):
>> return BitAnd()(self.expr, other)
>>
>> then you'd use the MyInt datatype in your mappings where you want your
>> special operator to take place.
>>
>> If you want the base Integer to do this, you'd need to monkeypatch the
>> comparator, this is less recommended as it can cause surprises:
>>
>>
>> class comparator_factory_mixin(object):
>> def __and__(self, other):
>> return BitAnd()(self.expr, other)
>>
>> Integer.Comparator.__bases__ = (comparator_factory_mixin, ) +
>> Integer.Comparator.__bases__
>>
>>
>>
>>
>>
>> > --
>> > 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
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>
> --
>
> Антон
>
> --
> 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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--
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
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