Is it possible to inject parameters values into already compiled statement without recompiling?

[Andrei Pashkin]

Let's suppose I have a compiled SA expression statement which I want to cache to avoid repetitive compilation. Let's also suppose that I can't use "literal_binds" because I want to provide parameter values late, after getting the compiled query from the cache. 

Is it somehow possible to inject values into compiled query without executing it?

Here is a full example:

https://gist.github.com/AndreiPashkin/9b497233e2a7668d0da67dc74d169812

[Mike Bayer]

When you execute a compiled statement using Core there is always a dictionary of parameters you pass along.    Whatever parameters you put here take precedence.    in your example you're using bindparam() directly, so this is the easiest case, just pass "id":

def my_cached_thing():

    cache = {}

    stmt = sa.select([User.__table__]).where(User.__table__.c.id == sa.bindparam('id'))

    def go(engine, id):

        with engine.connect() as conn:

            return conn.execution_options(compiled_cache=cache).execute(stmt, id=id)

    return go

# in your code

cached_lookup = my_cached_thing()

for id in [1, 10, 15, 27, 19, 38]:

    result = cached_lookup(engine, id)   # will only compile the statement once

    # ... etc

The above thing I did with the nested function etc. is arbitrary, just the main point is, same statement object and same cache dictionary.     as stated before, 1.4 will hopefully have an improvement to make all of this transparent.

 

Also note you can use Core select() constructs etc with the ORM classes directly:

select([User]).where(User.id == bindparam('id'))

--

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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[Andrei Pashkin]

Yes, you are right, thank you, Mike.

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