Duplicate associations from multiple association tasks

[dvogel]

Each time the association task is run it duplicates previously-found associations. Below is an example of 2 associations from 2 association tasks, but it seems to go on without limit.

$ curl --data-urlencode "title=Lorem ipsum" --data-urlencode "text@/tmp/loremipsum.txt" http://localhost:8080/document/1/1/
{"id":"513117167da2803b40000001","command":"Add Document","source":null,"target":{"doctype":1,"docid":1},"sourceRange":"","targetRange":"","status":"Queued","error":"","success":true}
$ curl http://localhost:8080/document/1/1/ | python -m json.tool
{
    "characters": 57, 
    "id": {
        "docid": 1, 
        "doctype": 1
    }, 
    "text": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.\n", 
    "title": "Lorem ipsum", 
    "valid": true
}
$ curl -XPOST http://localhost:8080/association/1/1/
{"id":"513117217da2803b40000002","command":"Associate Document","source":null,"target":null,"sourceRange":"1","targetRange":"1","status":"Queued","error":"","success":true}
$ curl http://localhost:8080/document/1/1/ | python -m json.tool
{
    "associations": {
        "Documents": [
            {
                "characters": 57, 
                "fragment_count": 1, 
                "fragments": [
                    [
                        0, 
                        0, 
                        55, 
                        239133750739
                    ]
                ], 
                "id": {
                    "docid": 1, 
                    "doctype": 1
                }, 
                "title": "Lorem ipsum", 
                "valid": true
            }
        ], 
        "Meta": {}
    }, 
    "characters": 57, 
    "id": {
        "docid": 1, 
        "doctype": 1
    }, 
    "text": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.\n", 
    "title": "Lorem ipsum", 
    "valid": true
}
$ curl -XPOST http://localhost:8080/association/1/1/
{"id":"513117267da2803b40000003","command":"Associate Document","source":null,"target":null,"sourceRange":"1","targetRange":"1","status":"Queued","error":"","success":true}
$ curl http://localhost:8080/document/1/1/ | python -m json.tool
{
    "associations": {
        "Documents": [
            {
                "characters": 57, 
                "fragment_count": 1, 
                "fragments": [
                    [
                        0, 
                        0, 
                        55, 
                        239133750739
                    ]
                ], 
                "id": {
                    "docid": 1, 
                    "doctype": 1
                }, 
                "title": "Lorem ipsum", 
                "valid": true
            }, 
            {
                "characters": 57, 
                "fragment_count": 1, 
                "fragments": [
                    [
                        0, 
                        0, 
                        55, 
                        239133750739
                    ]
                ], 
                "id": {
                    "docid": 1, 
                    "doctype": 1
                }, 
                "title": "Lorem ipsum", 
                "valid": true
            }
        ], 
        "Meta": {}
    }, 
    "characters": 57, 
    "id": {
        "docid": 1, 
        "doctype": 1
    }, 
    "text": "Lorem ipsum dolor sit amet, consectetur adipiscing elit.\n", 
    "title": "Lorem ipsum", 
    "valid": true
}