On Thu, Jan 7, 2010 at 2:02 PM, Mario Briggs <mario.bri...@in.ibm.com> wrote:
> Russ,
>
> The indexing that Oracle is supporting is 'index-on-expression'. DB2
> also supports that, but it isnt enabled for character long columns,
> since they hadnt had a request for that. I talked to the DB2 server
> folks about these use-cases and they have agreed to support this via
> index-on-expression shortly. For the immediate needs, Rahul is going
> to look at supporting this via 'hidden' columns - Whenever there is a
> text field with an index specified, the backend will create a hidden
> and generated column (poplated with first X chars of the text field).
> The index will be created on this hidden column. When there is a
> lookup by value, the backend will actually do the lookup on the hidden
> indexed column. - you see any blockers to this ?
I'm not sure what you're asking me. "Blockers" of what?
I know almost nothing about DB2; I know only slightly more about
Oracle. I can only advise you on what Django does. In this case, the
code tells you everything you need to know: Django needs to be able to
issue the following query:
action_list = LogEntry.objects.filter(
object_id = object_id,
content_type__id__exact =
ContentType.objects.get_for_model(model).id
).select_related().order_by('action_time')
As long as you can satisfy that requirement, you've done everything
you need to do.
> BTW, index is not turned ON on LogEntry.object_id. Do you feel this
> use-case usage is low to warrant that ?
I can't say the lack of an index on that field has been a performance
problem on any site I've managed, and I don't recall seeing any
reports on the mailing list or Trac that indicate that it has caused a
problem for anyone else.
Yours,
Russ Magee %-)
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