On 03/02/2016 03:29 PM, Brian Cherinka wrote:
Hi,
After a query has been constructed with some filter conditions applied,
but before the query has been run, what's the best way to replace the
attribute in the filter clause?
Let's say I have a query like this
|
q =session.query(Cube).join(Version).filter(Version.version =='v1_5_1')
|
and I can print the filters with and without the values bound
|
printq.whereclause
version.version =:version_1
q.whereclause.compile(compile_kwargs={'literal_binds':True})
version.version ='v1_5_1'
|
What's the best way to replace the attribute with a new parameter, like
version = 'v1_3_3'?
use a bound parameter from the start, use params():
q = s.query(Cube).join(Version).filter(Version.whatever == bindparam('x'))
results = q.params(x='1234').all()
For a single condition, the type of whereclause is a BinaryExpression,
and I figured out that left, operator, and right, get me the left-hand,
right-hand side of the clause and the operator. And I can modify the
value with
|
q.whereclause.right.value='v1_3_3'
|
|
printq.whereclause.compile(compile_kwargs={'literal_binds':True})
version.version ='v1_3_3'
|
Is this the best way?
My bigger problem is I have a list of clauses in my query
|
t =session.query(Cube).join(Version,Sample).filter(Version.version
=='v1_5_1',Sample.x <10)
|
now the t.whereclause is a BooleanClauseList and I can't figure out how
to iterate over this list, such that I can do the above, and modify the
version value in place. What's the best way to do this? I can't find
the proper location in the documentation that describes a
BooleanClauseList. Searching for it returns 0 results.
Thanks.
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