invalid argument type in call to function 'ATTRIBUTES()' in ArangoDB

Question

I have stored my Data in the give formate in AreangoDB, My collection name in DSP:

 "data": {
"1":   [ {"db_name": "DSP"}, {"rel": "2"} ], 
"2":   [ {"rel_name": "DataSource"}, {"tuple": "201"}, {"tuple": "202"}, {"tuple": "203"} ],
"201": [ {"src_id": "Pos201510070"}, {"src_name": "Postgres"}, {"password": "root"}, {"host": "localhost"}, {"created_date": "20151007"}, {"user_name": "postgres"}, {"src_type": "Structured"}, {"db_name": "postgres"}, {"port": "None"} ],
"202": [ {"src_id": "pos201510060"}, {"src_name": "Postgres"},{"password": "root"}, {"host": "localhost"}, {"created_date": "20151006"}, {"user_name": "postgres"}, {"src_type": "Structured"}, {"db_name": "DSP"}, {"port": "5432"} ],
"203": [ {"src_id": "pos201510060"}, {"src_name": "Postgres"}, {"password": "root"}, {"host": "localhost"}, {"created_date": "20151006"}, {"user_name": "postgres"},{"src_type": "Structured"},{"db_name": "maindb"},{"port": "5432"} ]
}

I am executing a query with the above data in the following format:

  FOR p IN NestedDSP
  LET attributes = ATTRIBUTES(p) 
  FOR attribute IN attributes 
      LET key = ATTRIBUTES(attribute)[0] 
      LET value = attribute[key] 
      RETURN { subject: attribute, predicate: key, object: value }

When I submit my query to ArangoDB, it returns the response as:

    Warnings:

[1542], 'invalid argument type in call to function 'ATTRIBUTES()''
[1542], 'invalid argument type in call to function 'ATTRIBUTES()''
[1542], 'invalid argument type in call to function 'ATTRIBUTES()''
[1542], 'invalid argument type in call to function 'ATTRIBUTES()''

Result:

[
  {
    "subject": "data",
    "predicate": null,
    "object": null
  },
  {
    "subject": "_id",
    "predicate": null,
    "object": null
  },
  {
    "subject": "_rev",
    "predicate": null,
    "object": null
  },
  {
    "subject": "_key",
    "predicate": null,
    "object": null
  }
]

Please tell me what is the problem with this query, and why the answer is like the above..I am working in ArangoDB-2.7.3-win64.

Thanks

Answer 1

Let me demonstrate how to construct such a complex query digging deep into nested data structures. I start out taking the outer parts of the query, to have an inner result:

FOR p IN NestedDSP
  LET attributes = ATTRIBUTES(p) 
  FOR attribute IN attributes 
      RETURN attribute

which gives me:

[ 
  "data", 
  "_rev", 
  "_key", 
  "_id" 
]

So lets dive deeper into the next layer. I guess you're only interested in the values present underneath data key right? so we pick p.data:

FOR p IN NestedDSP
  LET attributes = ATTRIBUTES(p.data) 
  FOR attribute IN attributes 
      RETURN attribute

which then gives me the keys for your next inner array:

[ 
  "203", 
  "202", 
  "201", 
  "2", 
  "1" 
]

We now explore what we find attached to these nodes:

FOR p IN NestedDSP
  LET attributes = ATTRIBUTES(p.data) 
  FOR oneAttribute IN attributes 
    LET keys = p.data[oneAttribute]
      RETURN keys

Its Again an array, which we need to iterate into using a FOR loop over keys:

[
  [ 
    { 
      "src_id" : "pos201510060" 
    }, 
    { 
      "src_name" : "Postgres" 
    }, ...

We add this additional FOR-loop:

FOR p IN NestedDSP
  LET attributes = ATTRIBUTES(p.data) 
  FOR oneAttribute IN attributes 
    LET keys = p.data[oneAttribute]
    FOR key IN keys
      RETURN key

we get the inner most objects:

[ 
  { 
    "src_id" : "pos201510060" 
  }, 
  { 
    "src_name" : "Postgres" 
  }, 
  { 
    "password" : "root" 
  }, 
...

You wanted to use the ATTRIBUTES function, but the objects only have one member, so we can access [0]:

FOR p IN NestedDSP
  LET attributes = ATTRIBUTES(p.data) 
  FOR oneAttribute IN attributes 
    LET keys = p.data[oneAttribute]
    FOR key IN keys
      LET keyAttributes=ATTRIBUTES(key)
        RETURN keyAttributes

Which gives us the object keys, one per inner most object:

[ 
  [ 
    "src_id" 
  ], 
  [ 
    "src_name" 
  ], 

We inspect whether we now get only the object keys of the inner most structure; we pick the variable names a little more clever than above:

  FOR p IN NestedDSP
    LET attributes = ATTRIBUTES(p.data) 
    FOR oneAttribute IN attributes 
      LET pairs = p.data[oneAttribute]
      FOR onePair IN pairs
        LET pairKey=ATTRIBUTES(onePair)[0]
          RETURN pairKey

YES:

[ 
  "src_id", 
  "src_name", 
  "password", 
  "host", 
    ...

So now its time to construct the results object as you wanted them:

  FOR p IN NestedDSP
    LET attributes = ATTRIBUTES(p.data) 
    FOR oneAttribute IN attributes 
      LET pairs = p.data[oneAttribute]
      FOR onePair IN pairs
        LET pairKey=ATTRIBUTES(onePair)[0]
          RETURN { subject: oneAttribute, predicate: pairKey, object: onePair[pairKey] }

The subject is the number identifying the outermost item, the predicate is the object key, and the object is the value in it:

[ 
  { 
    "subject" : "203", 
    "predicate" : "src_id", 
    "object" : "pos201510060" 
  }, 
  { 
    "subject" : "203", 
    "predicate" : "src_name", 
    "object" : "Postgres" 
  }

Which is hopefully what you wanted?