I'm afraid I won't be able to help with the Cassandra question.
However, I did want to point out that there is no need for these
results and queries to be real-time. For this particular feed,
anonymous users only need to see things that are public, and logged in
users only need to see things that are public or visible to logged in
users. I think that means that the results can be published and
cached, and re-published from time to time.
Not sure if this changes anything, but maybe it can be helpful.
Kind regards,
Nicolaas
On 19 Jul 2012, at 01:02, Chris Tweney wrote:
> I just submitted a pull request for KERN-3036 [1] that seemed way
> harder
> than it should be thanks to our Solr-plus-KV architecture. I'd like to
> challenge those who know a lot about Cassandra to see if that platform
> would make it easier to fix this issue.
>
> Capsule version: To support /var/search/activity/all.json, we need a
> query that returns all the activities that point to nodes to which I
> have read permission. The read permission inheres in the nodes
> themselves, not in the activities (which just inherit their parents'
> permissions).
>
> In a relational model it's an easy problem: Just a three-table join
> from
> Activity to Node to Permission.
>
> In Solr, the fix was less straightforward. Solr joins (documented at
> [2]) are not fully equivalent to SQL joins. In particular, they're
> more
> like inner queries than like true SQL joins. Also, joins between two
> different types of documents must be made on fields that the two
> document types do NOT share. In other words the foreign key has to
> have
> a different name from the key it points to. These constraints made it
> tricky, but I did finally find the right Solr syntax for this search:
>
> q=resourceType[* TO *]&fq={!join from=path
> to=activitysource}(readers:anonymous OR readers:everyone)
>
> Does Cassandra make this case any easier? If so, show me how!
>
> -chris
>
> [1] https://jira.sakaiproject.org/browse/KERN-3036
>
> [2] http://wiki.apache.org/solr/Join
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