Enable multiple node types for single relationship type table about kuzu HOT 4 CLOSED

Hi @d33bs , this is a good topic. I've got one input here: One work around we have right now is REL TABLE GROUP, which can life some limitation of "each REL table in Kuzu may only contain one node type for the FROM and TO specification".

Edit: Oh wasn't aware that @andyfengHKU has a more detailed answer. Pleaser refer to his one for more details. 😄

from kuzu.

Hi @d33bs, thanks for trying us out!

Indeed for some graph databases, a relationship (REL table) can be defined over multiple node tables, e.g. the following is doable in Neo4j

CREATE (:A)-[e:R]->(:B);
CREATE (:C)-[e:R]->(:D);
MATCH ()-[e:R]->() RETURN e;

Here we define a relationship R over FROM A TO B and FROM C TO D. The above statements can also be rewritten as with multi-label query which is exactly the same as your second workaround suggestion.

CREATE (:A)-[e:R_AB]->(:B);
CREATE (:C)-[e:R_CD]->(:D);
MATCH ()-[e:R_AB|:R_CD]->() RETURN e;

Back in the day, we thought since there was a workaround, we could just go for a simpler modelling which also benefits bulk-loading performance, data compression and other system level optimizations. So we chose to constraint REL table to be defined over one pair of FROM TO node tables.

Though slowly we indeed receive feedbacks about the limitation of this constraint in practice. So we introduced REL GROUP as an experimental feature where you can define a rel group and use it as a union of multiple relationship tables during querying.

CREATE REL TABLE GROUP R (FROM A TO B, FROM C TO D);
MATCH ()-[e:R]->() RETURN e;

This feature is quite experimental so it comes with many limitations, e.g. you can not bulk-load into a rel group. Any feedback over this feature is highly appreciated.

As for the workarounds

Generalize all NODE types to a single table of type

I don't recommend this one because it will definitely hurt performance because a node table scan will be a lot more costly.

Create specific REL tables for each kind of relationship by distinct FROM, TO node pairs

This idea aligns with our initial thoughts and I believe it will work fine.

from kuzu.

Thank you so much @ray6080 and @andyfengHKU ! I'll give REL GROUP's a try and follow up with any feedback.

from kuzu.

I'm closing this issue for now assuming RelGroup will do for now. Please re-open if your feedback has a request for a feature we should consider.

from kuzu.