Non-deterministic inclusion of empty string by exists filter

[takism1]

This happens with 1.3.4. Repeating these steps enough times I sometimes get both documents returned by the filter and sometimes only the one with the non-empty string.

Delete the index

$ curl -XDELETE localhost:9200/test

Insert 2 documents using bulk API (one has empty string and one does not)

$ cat requests
    { "index" : { "_index" : "test", "_type" : "test", "_id" : "1" } }
    { "title": "" }
    { "index" : { "_index" : "test", "_type" : "test", "_id" : "2" } }
    { "title": "Test document" }
$ curl -XPOST localhost:9200/_bulk --data-binary @requests

This filter sometimes returns only document 2 and sometimes both

$ curl -XPOST localhost:9200/test/_search?pretty -d '
{
    "filter": {
        "exists": {
            "field": "title"
        }
    }
}'

I suspect it may have to do with the order in which the documents are indexed by the bulk API. But in http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/_batch_processing.html it is mentioned that "The bulk API executes all the actions sequentially and in order" so I am wondering if this is a bug.

[jpountz]

I think this is due to the fact that elasticsearch does not generate dynamic mappings for the empty string. Additionally, your documents likely go to different shards, so they are processed in parallel, the order is not defined.

The mapping for title is created by the document that has a non empty title. And sometimes it occurs before the document with an empty title is indexed (when you have 2 matches), sometimes after (when you have 1 match).

I believe this would be fixed by creating dynamic mappings for empty strings but I'm unsure about side effects it could have.