filterTwoArguments not working

[neonstalwart]

it looks like filterTwoArguments doesn't work.

db.search([
    {
        subject: user,
        predicate: 'like',
        object: db.v('liked')
    },
    {
        subject: db.v('someone'),
        predicate: 'like',
        object: db.v('liked'),
        filter: function (triple, cb) {
            cb(null, triple);
        }
    }
])

what i'm trying to do is to filter out all the things already liked by user. i realize that i can do this with a filter on the results but i was thinking that maybe it's better for performance to filter on the query rather than the results but i'm open to hearing that it's not.

[neonstalwart]

i think this is broken for filtering results too. i'll try to confirm tomorrow and hopefully produce a test case and fix.

[mcollina]

Thanks, I have no bandwidth for LG at the moment :/.

[neonstalwart]

i seem to have found more issues while trying to write tests for this one. maybe my mental model is wrong so i'm not going to try to fix anything until i hear from you about #105 and in particular #105 (comment)

[jbuck167]

Update: I looked at filterTwoArguments and it was not the cause of the problem I found. I was able to repeat the issue with filterOneArgument. I have found a problem with the joinstream that is due to control flow of the various streams involved in a search. Please see #186

---

Hello! I am here because I replicated the problem originally posted. To summarize the problem, there is an issue when doing searches with an array of triples where there is a filter function in one or more of the triples in the array other than the first triple.

Example problematic search:
db.search([triple1, triple2, ..., tripleN])

where at least one of the triples other than triple1 has a filter like the following:

triple2 = {
   subject: db.v(var1)
   filter: function(triple) {
      return true;      
   }
}

I tried several combinations of using filters inside of search triples. I found that putting a filter in a search triple other than the first triple in the array caused the search to never resolve. The search will work if there is a filter in the first triple of the array only:

This worked for me:

db.search([
    {
        subject: db.v('someone'),
        predicate: 'like',
        object: db.v('liked'),
        filter: function (triple, cb) {
            cb(null, triple);
        }
    },
    {
        subject: user,
        predicate: 'like',
        object: db.v('liked')
    }
])

I was able to replicate this with many examples. As long as there were no filters after the first triple, I got results. If there was a filter in any triple other than the first, the search never resolves. I also tested filtering full solutions and there were no problems there. Also interesting: the filters at the triple scope are always executed, and the full solution filter is also executed. Despite this, the search still does not resolve if there was a filter in any but the first triple in the search.

Working Example:

db.search([
    {
        subject: db.v('someone'),
        predicate: 'like',
        object: db.v('liked'),
        filter: function (triple, cb) {
            cb(null, triple);
        }
    },
    {
        subject: user,
        predicate: 'like',
        object: db.v('liked')
    }
], { 
   filter: function(solution, callback) {
      callback(null, solution);
   }
})

Broken Example:

db.search([
    {
        subject: user,
        predicate: 'like',
        object: db.v('liked')
    },
    {
        subject: db.v('someone'),
        predicate: 'like',
        object: db.v('liked'),
        filter: function (triple, cb) {
            cb(null, triple);
        }
    }
], { 
   filter: function(solution, callback) {
      callback(null, solution);
   }
})