Todays note about performance is a note about some storm/sqlobject glue.
Code like this:
...
if bugtask.distribution is None:
...
is probably wrong: it should be
...
if bugtask.distributionID is None:
...
I say this because the former code will trigger late evaluation of the
related distribution object *which we then don't use*. The second form
won't trigger late evaluation, and thus is faster / can run with
narrower DB permissions.
The underlying cause for this is the difference between
ReferenceColumn and IntColumn in storm.
In 'raw' storm, we create *two* attributes on a model table - something like:
distribution_id = IntColumn('distribution', ...)
distribution = Reference(table='distribution', foreign_key=distributribution_id)
But in storm.sqlobject we use some magic, and instead do:
distribution = ForeignKey(dbname=distribution, foreignkey='Distribution')
which creates a ReferenceColumn distribution *and* an IntColumn distributionID.
Accessing .distribution will *always* trigger a DB query against the
Distribution table. Accessing .distributionID will *never* trigger
such a query.
The rule of thumb is : unless you *want* the distribution object
itself, never access the attribute.
I mention this because just last night another case of this confusion
caused a bug (which I think JTV has a fix for landing already). I've
seen several cases of unnecessary late evaluation caused by this
distinction not being honoured.
-Rob
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