Ed Singleton wrote:
> To partially clarify and answer my own question here (I was very tired
> by the time I pasted this last night)
>
> In the case of:
>
> sa
> .insert
> (mytable
> ).values(myothertable.select().filter_by(foo=sa.bindparam("bar"))
>
> This doesn't currently work because the bindparam required for the
> select statement gets discarded. Having gone through the way SA
> compiles statements, it appears that parameters are used to fill in an
> insert statements values. The only way I can see of getting around
> this is that at the time of adding the values, they bindparams are
> extracted from the select and added to a new attribute on the insert
> statement, and around the time of creating the ExecutionContext, they
> are processed and added back into the query.
>
> My previous question about getting both the column names and the
> bindparams, I managed to solve by (duh!) getting the column names,
> compiling the select statement and then getting the bindparams. I
> would still be interested to know where the bindparams are stored in
> an uncompiled select though. I couldn't work it out.
>
> Sorry if all this is a little fuzzy. It's my first time at really
> trying to understand what SA does behind the scenes.
if you're using the @compiler extension to generate this, the same
compiler object would generate the string representation of both the
insert() and the select(), gathering bindparam() objects from the
structure as it goes. the params structure embedded on the Compiled at
the end is what gets sent to execute() along with any ad-hoc values.
The example here:
http://www.sqlalchemy.org/docs/reference/ext/compiler.html?highlight=compiler#compiling-sub-elements-of-a-custom-expression-construct
should accomplish all this.
>
> Thanks
>
> Ed
>
>
> On 11 Feb 2010, at 22:23, Ed Singleton wrote:
>
>> I've been having a clumsy hack at enabling myself to pass a select
>> statement as a value to an insert statement. IE:
>> sa.insert(mytable).values(myothertable.select())
>>
>> I've got it working in that most basic case, but I'm struggling when
>> the select statement has bindparams. The insert needs to take them,
>> as well as (for some dialects) the column names of the select. The
>> thing is I can work out how to get the bindparams from a compiled
>> statement, and I can work out how to get the column names from a
>> uncompiled statement, but I can't work out how to get both from one
>> or the other. Any hints on this would be appreciated.
>>
>> Also, I slightly worried that there's an obvious reason why this
>> hasn't been done before. Is there something stupid I'm missing? If
>> anyone's tried patching SA to do this I would greatly appreciate any
>> advice.
>>
>> Thanks
>>
>> Ed
>
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