suggestion: Not to throw when no edges created.

Currently, CREATE EDGE throws an exception when FROM statement or TO statement were not found.

https://github.com/orientechnologies/orientdb/blob/ad7cbed6c7c5b3f920713d93bc8c98b219c200c8/graphdb/src/main/java/com/orientechnologies/orient/graph/sql/OCommandExecutorSQLCreateEdge.java#L213-L219

        if (edges.isEmpty()) {
          if (fromIds.isEmpty())
            throw new OCommandExecutionException("No edge has been created because no source vertices");
          else if (toIds.isEmpty())
            throw new OCommandExecutionException("No edge has been created because no target vertices");
          throw new OCommandExecutionException("No edge has been created between " + fromIds + " and " + toIds);
        }

Imagine you want to create possibly multiple edges from a RID to a sub-query. The result of sub-query could be empty, it’s not deterministic. If you want to make sure that the edges will be created, than you should select-and-create in a transaction. Why don’t you let it go and just return a number of edges that actually created. I think it’s not only easier to handle it, but also give better performance.

[ahlbejes]

+1 It is really the behavior I expected. It is a hassle to have to be sure both source and destination sets are not empty before executing the create edge command, or to have to handle the exception messages.

[luigidellaquila]

Hi guys,

The general case is that you can create a set of edges from a set of vertices to another set of vertices.

By definition, sets can be empty, so it makes sense to just create no edges.

-1 to the idea of adding another keyword, the language is already too cluttered by keywords to manage corner cases, the statement will just return the number of edges that were created.