Is it possible to use bindparam() for whole where expression?

[Andrei Pashkin]

Hello!

I wonder - is it possible to parametrize where expression as a whole like that: 

select([users_table]).where(bindparam('criteria'))

?

My use case is that I'd like to pre-compile a complex SQLAlchemy expression to avoid redundant computations and achieve the same effect as Bakery has for the ORM but only for a low-level SA expression.

[Mike Bayer]

On Mon, Jan 20, 2020, at 1:46 PM, Andrei Pashkin wrote:

Hello!

I wonder - is it possible to parametrize where expression as a whole like that: 

select([users_table]).where(bindparam('criteria'))

nope, that's not how SQL bound parameters work.

?

My use case is that I'd like to pre-compile a complex SQLAlchemy expression to avoid redundant computations and achieve the same effect as Bakery has for the ORM but only for a low-level SA expression.

Wait for SQLAlchemy 1.4, this will have that feature.

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[Mike Bayer]

On Mon, Jan 20, 2020, at 2:26 PM, Mike Bayer wrote:

On Mon, Jan 20, 2020, at 1:46 PM, Andrei Pashkin wrote:

Hello!

I wonder - is it possible to parametrize where expression as a whole like that: 

select([users_table]).where(bindparam('criteria'))

nope, that's not how SQL bound parameters work.

?

My use case is that I'd like to pre-compile a complex SQLAlchemy expression to avoid redundant computations and achieve the same effect as Bakery has for the ORM but only for a low-level SA expression.

Wait for SQLAlchemy 1.4, this will have that feature.

noting also, there is a cache feature for Core statements right now, you just have to use the same statement object each time, since currently the statement object itself is the cache key.  See https://docs.sqlalchemy.org/en/13/core/connections.html?highlight=compiled_cache#sqlalchemy.engine.Connection.execution_options.params.compiled_cache .  This is what BakedQuery ultimately uses also and the unit of work uses it also.

In 1.4 all statements will be able to generate a separate cache key that is repeatable for multiple instances of the same statement.

[Andrei Pashkin]

Alright, thank you very much! Very informative.

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