Elasticsearch 2.x index mapping _id - elasticsearch

Question

I ran ElasticSearch 1.x (happily) for over a year. Now it's time for some upgrading - to 2.1.x. The nodes should be turned off and then (one-by-one) on again. Seems easy enough.
But then I ran into troubles. The major problem is the field _uid, which I created myself so that I knew the exact location of a document from a random other one (by hashing a value). This way I knew that only that the exact one will be returned. During upgrade I got
MapperParsingException[Field [_uid] is a metadata field and cannot be added inside a document. Use the index API request parameters.]
But when I try to map my former _uid to _id (which should also be good enough) I get something similar.
The reason why I used the _uid param is because the lookup time is a lot lower than a termsQuery (or the like).
How can I still use the _uid or _id field in each document for the fast (and exact) lookup of certain exact documents? Note that I have to call thousands exact ones at the time, so I need an ID like query. Also it may occur the _uid or _id of the document does not exist (in that case I want, like now, a 'false-like' result)
Note: The upgrade from 1.x to 2.x is pretty big (Filters gone, no dots in names, no default access to _xxx)
Update (no avail):
Updating the mapping of _uid or _id using:
final XContentBuilder mappingBuilder = XContentFactory.jsonBuilder().startObject().startObject(type).startObject("_id").field("enabled", "true").field("default", "xxxx").endObject()
.endObject().endObject();
CLIENT.admin().indices().prepareCreate(index).addMapping(type, mappingBuilder)
.setSettings(Settings.settingsBuilder().put("number_of_shards", nShards).put("number_of_replicas", nReplicas)).execute().actionGet();
results in:
MapperParsingException[Failed to parse mapping [XXXX]: _id is not configurable]; nested: MapperParsingException[_id is not configurable];
Update: Changed name into _id instead of _uid since the latter is build out of _type#_id. So then I'd need to be able to write to _id.

Answer 1

Since there appears to be no way around setting the _uid and _id I'll post my solution. I mapped all document which had a _uid to uid (for internal referencing). At some point it came to me, you can set the relevant id
To bulk insert document with id you can:
final BulkRequestBuilder builder = client.prepareBulk();
for (final Doc doc : docs) {
builder.add(client.prepareIndex(index, type, doc.getId()).setSource(doc.toJson()));
}
final BulkResponse bulkResponse = builder.execute().actionGet();
Notice the third argument, this one may be null (or be a two valued argument, then the id will be generated by ES).
To then get some documents by id you can:
final List<String> uids = getUidsFromSomeMethod(); // ids for documents to get
final MultiGetRequestBuilder builder = CLIENT.prepareMultiGet();
builder.add(index_name, type, uids);
final MultiGetResponse multiResponse = builder.execute().actionGet();
// in this case I simply want to know whether the doc exists
if (only_want_to_know_whether_it_exists){
for (final MultiGetItemResponse response : multiResponse.getResponses()) {
final boolean exists = response.getResponse().isExists();
exist.add(exists);
}
} else {
// retrieve the doc as json
final String string = builder.getSourceAsString();
// handle JSON
}
If you only want 1:
client.prepareGet().setIndex(index).setType(type).setId(id);
Doing - the single update - using curl is mapping-id-field (note: exact copy):
# Example documents
PUT my_index/my_type/1
{
"text": "Document with ID 1"
}
PUT my_index/my_type/2
{
"text": "Document with ID 2"
}
GET my_index/_search
{
"query": {
"terms": {
"_id": [ "1", "2" ]
}
},
"script_fields": {
"UID": {
"script": "doc['_id']"
}
}
}