Does the elasticsearch ID have to be unique to a type or to the index? - elasticsearch

Question

Elasticsearch allows you to store a _type along with the _index. I was wondering if I were to provide my own _id should it be unique across the index?

Answer 1

It should be unique together
PUT so
PUT /so/t1/1
{}
PUT /so/t2/1
{}
GET /so/_search
{
"took": 1,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 2,
"max_score": 1,
"hits": [
{
"_index": "so",
"_type": "t2",
"_id": "1",
"_score": 1,
"_source": {}
},
{
"_index": "so",
"_type": "t1",
"_id": "1",
"_score": 1,
"_source": {}
}
]
}
}
And the reason for that: you'd never get documents by index w/o knowing doctype, and querying ES with index-wide query will return documents including their types and indexes.

Answer 2

Absolutely, there are a few ways of doing it.
The first is using the PUT API, which allows us to specify an ID for a document. So, for the index index and the type type:
curl -XPUT "http://localhost:9200/index/type/1/" -d'
{
"test":"test"
}
Which gives me this document:
{
"_index": "index",
"_type": "type",
"_id": "1",
"_score": 1,
"_source": {
"test": "test"
}
}
Another way is to route the ID to a unique field in your mapping. For example, an md5 hash. So, for an index called index with a type called type, we can specify the following mapping:
curl -XPUT "http://localhost:9200/index/_mapping/type" -d'
{
"type": {
"_id":{
"path" : "md5"
},
"properties": {
"md5": {
"type":"string"
}
}
}
}
This time, I'm going to use the POST API, which automatically generates an ID. If you haven't specified a path in your mapping, it will automatically generate one for you.
curl -XPOST "http://localhost:9200/index/type/" -d'
{
"md5":"00000000000011111111222222223333"
}'
Which gives me the following document in a search:
{
"_index": "index",
"_type": "type",
"_id": "00000000000011111111222222223333",
"_score": 1,
"_source": {
"md5": "00000000000011111111222222223333"
}
}
The second method is generally preferred, because it provides consistency across the index. A perfectly valid id for an index could be 1 like in the example, or dog in another case.