Query two relationships at a time in elgg_get_entity_from_relationships (Trac #2850)

[elgg-gitbot]

Original ticket http://trac.elgg.org/ticket/2850 on 41094667-04-17 by trac user dannyl, assigned to unknown.

Elgg version: 1.7

Right now elgg_get_entity_from_relationships can only handle querying based on one relationship at a time. It seems like it would make sense to be able to query based on two - for example: get all members of a group who are also a logged in user's friends.

D

[elgg-gitbot]

Milestone changed to Elgg 1.7.8 by brettp on 41095698-04-14

[elgg-gitbot]

Milestone changed to Elgg 1.7.9 by cash on 41207497-01-27

[elgg-gitbot]

Milestone changed to Needs Review by cash on 41347210-01-22

[elgg-gitbot]

cash wrote on 41418388-09-02

1. Where does it stop? Just two relationships at a time or do we allow any arbitrary n relationships?
2. Do we support multiple one hop constraints or do we allow multiple hop queries?

Examples:

One hop: * isFriendOf use[svn:1] AND * memberOf group1
[[BR]]Give me all the people who are friends of use[svn:1] who are also members of group1

Two hop: * isFriendOf ? AND ? memberOf group1
[[BR]]Give me all the people who are friends of a person who are members of group1

Right now we allow people to query based on multiple metadata (and it is possible for people to create really slow queries). It seems reasonable to provide similar support for relationships.

We have only had a single case that I can recall where we needed this and we did it through a custom where clause.

[elgg-gitbot]

trac user dannyl wrote on 41418835-04-17

I agree. The one case we had - we also handled with custom where clause

I think we can close the ticket

[elgg-gitbot]

Milestone changed to Elgg 1.9 by brettp on 41609863-01-21

[ewinslow]

I can envision some more handy use-cases (e.g. sharing with extended friends/friends-of-friends), but even that could be handled by computing the result and storing it explicitly in the DB so the query is only a one-hop.

And at the end of the day, I imagine if someone did need something this advanced and wanted to do so in a performant way, we're probably talking about using a real graph DB like Neo4J, rather than Elgg's relational structure.