Hi Nick,
Thanks for replying, that made the things a bit more clear. But I
still don't understand the reasoning behind it.
You said the following example
Foo.all().filter('tags =', foo).filter('tags =', bar).order('bar')
will result in an exploding index.
But why so?
I believe above statement is equivalent to:
select * from Foo where tags='foo' AND tags = 'bar' order by 'bar1'
I changed 'bar' to 'bar1' just to avoid confusion.
Now since the order by is applied to 'bar1' and not to 'tags'(can that
be even done??) why will two separate indexes be required. I
understand they can be required if order by is applied on tags
somehow, but for this case an index with default ordering for
listproperty class could have been used.
The non exploding index that can be used here is:
- kind: Foo
property:
- tags
- bar1
direction:desc
Or will this not work for the query in question?
Thanks for bearing with me.
On Jul 27, 12:56 pm, "Nick Johnson (Google)" <nick.john...@google.com>
wrote:
> Hi Jai,
>
> Both your example and my original example are cases of exploding indexes. In
> my example, indexing on the same listproperty twice is required for certain
> queries (for example, the Foo.all().filter('tags =', foo).filter('tags =',
> bar).order('bar') example), but likewise results in an exploding index.
>
> -Nick Johnson
>
>
>
> On Mon, Jul 27, 2009 at 4:30 PM, Jai <sharma...@gmail.com> wrote:
>
> > Hi Kyle,
>
> > I think what Nick meant was this:
>
> > - kind: Foo
> > property: tags1
> > property: tags2
>
> > that is having two different properties of type ListProperty because
> > then the index will have rows for each combination of values for each
> > of the property and number of rows will be multiplication of number of
> > distinct values in the indexes.
>
> > For your case it is ok because, there will be a single index 'tags'
> > with an entity being referenced by the DIFFERENT tag values in the
> > SAME index. So the references might be multiple, number of rows will
> > still be linear.
>
> > Hope it helps.
>
> > Regards,
> > Jai
> > On Jul 27, 11:16 am, Kyle Jensen <kljen...@gmail.com> wrote:
> > > Hi Nick,
>
> > > I noticed that the dev server will automatically add indexes that
> > > appear to be exploding indexes when I run queries like the example
> > > above. Ie, if I do Foo.get_by_tags(['tag1', 'tag2']) the dev server
> > > will create an index in index.yaml that is identical to the one you
> > > posted above:
>
> > > - kind: Foo
> > > property: tags
> > > property: tags
>
> > > ** Is that index not required for the snippet Foo.get_by_tags(['tag1',
> > > 'tag2'])?
> > > ** What about Foo.get_by_tags(['tag1', 'tag2']).order('bar') where bar
> > > is an IntegerProperty
>
> > > Thanks for your help and sorry for my ignorance!!
> > > Kyle
>
> > > On Jul 27, 8:07 am, "Nick Johnson (Google)" <nick.john...@google.com>
> > > wrote:
>
> > > > Hi Kyle,
>
> > > > Exploding indexes only come into play when you're _defining_ indexes -
> > for
> > > > example, an index like this would be an exploding one:
>
> > > > - kind: Foo
> > > > property: tags
> > > > property: tags
>
> > > > As long as you can satisfy your queries using the built in merge join
> > > > support (which is the case in your example, where you don't specify
> > > > inequality filters or sort orders), you'll be fine.
>
> > > > -Nick Johnson
>
> > > > On Mon, Jul 27, 2009 at 3:50 PM, Kyle Jensen <kljen...@gmail.com>
> > wrote:
>
> > > > > Hi, I'd like to know if multiple equality filters on a ListProperty
> > > > > leads to exploding indexes.
>
> > > > > I have a model something like the following (python):
>
> > > > > class Foo(db.model):
> > > > > tags = db.ListProperty(db.Category)
>
> > > > > �...@classmethod
> > > > > def get_by_tags(cls, tags):
> > > > > query = cls.all()
> > > > > for tag in tags:
> > > > > query.filter('tags =', tag)
> > > > > return query
>
> > > > > I'd like to know if I can filter by an arbitrary number of tags
> > > > > without encountering the exploding index problem (its not clear to me
> > > > > from the docs).
>
> > > > > E.g., can I do
> > > > > query = Foo.get_by_tags(['tag0', 'tag1', 'tag2', 'tag3' .... 'tagN'])
>
> > > > > etc etc.
>
> > > > > Thanks! Kyle
>
> > > > --
> > > > Nick Johnson, Developer Programs Engineer, App Engine
>
> --
> Nick Johnson, Developer Programs Engineer, App Engine
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