I am using Grakn. I'd like to delete a duplicate entity with the same attribute value (name). This is what I have now:
test> match $p isa person, has name $n; get;
{$p id V4176 isa person; $n "John" isa name;}
{$p id V40968336 isa person; $n "John" isa name;}
I would like to delete the one with id V4176. However if I do the query below, it deletes both entities:
match $p isa person, has name "John"; delete $p;
How do I just delete one of the two?
Grakn assigns an auto-generated id to each instance. Although this id is generated by Grakn solely for internal use, it is indeed possible to find an instance with its Grakn id. To do so, we use the id keyword followed by the id assigned to the instance by Grakn.
match $p id V4176; delete $p;
Now, the reason your query
match $p isa person, has name "John"; delete $p;
deletes both entities is because both of them are person and has name John, so they both match you match clause.
You can find more information here https://dev.grakn.ai/docs/query/match-clause#one-particular-instance