Hey all. Long time lurker, first time poster.
I'm using sqlalchemy ORM. We have a fairly decent sized data set, and one
table has a pretty large number of columns, some of them with foreignkeys.
I found that limiting a query to specific columns speeds up the time it
takes to come back with a result by quite a bit (like 100x faster for this
one table, talking like over a second to just a few milliseconds
difference).
So I have a query that goes something like this:
q = dbsession.query(
Host.hostname,
Host.platform,
Host.ostype,
Host.buildstatus,
Host.created_on,
Host.created_by,
Host.modified_by,
Host.jobrunid).filter(Host.buildstatus != None).all()
I then pass that result through a few functions to validate/update some of
the fields. Problem is, I could do this on a regular Query result (q =
dbsession.query(Host).filter(Host.buildstatus != None).all()) but the
results I get back from this optimized query as posted above, I can't
modify those values, I get "AttributeError: can't set attribute".
I've been Googling this and searching through these posts, but I guess I
don't know the right terms to search on. I can't find anything in the
documentation talking about how to modify the results of a KeyedTuple query.
Normally I would do something like:
for x in q:
if pingresult(x.hostname) is False:
x.buildstatus = 'removed'
dbsession.commit()
dbsession.close()
But if q is a set of KeyedTuples, this won't work.
What's the speediest way to accomplish this task? Should I just stick to
querying all the columns (....query(Host)...) and just take the performance
hit?
--
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http://www.sqlalchemy.org/
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