Elasticsearch partial update script: Clear array and replace with new values - elasticsearch

Question

I have documents like:
{
MyProp: ["lorem", "ipsum", "dolor"]
... lots of stuff here ...
}
My documents can be quite big (but these MyProp fields are not), and expensive to generate from scratch.
Sometimes I need to update batches of these - it would therefore be beneficial to do a partial update (to save "indexing client" processing power and bandwidth, and thus time) and replace the MyProp values with new values.
Example of original document:
{
MyProp: ["lorem", "ipsum", "dolor"]
... lots of stuff here ...
}
Example of updated document (or rather how it should look):
{
MyProp: ["dolor", "sit"]
... lots of stuff here ...
}
From what I have seen, this includes scripting.
Can anyone enlighten me with the remaining bits of the puzzle?
Bounty added:
I'd like to also have some instructions of how to make these in a batch statement, if possible.

Answer 1

You can use the update by query API in order to do batch updates. This works since ES 2.3 onwards, otherwise you need to install a plugin.
POST index/_update_by_query
{
"script": {
"inline": "ctx._source.myProp += newProp",
"params": {
"newProp": "sit"
}
},
"query": {
"match_all": {}
}
}
You can of course use whatever query you want in order to select the documents on which MyProp needs to be updated. For instance, you could have a query to select documents having some specific MyProp values to be replaced.
The above will only add a new value to the existing array. If you need to completely replace the MyProp array, then you can also change the script to this:
POST index/_update_by_query
{
"script": {
"inline": "ctx._source.myProp = newProps",
"params": {
"newProps": ["dolor", "sit"]
}
},
"query": {
"match_all": {}
}
}
Note that you also need to enable dynamic scripting in order for this to work.
UPDATE
If you simply want to update a single document you can use the partial document update API, like this:
POST test/type1/1/_update
{
"doc" : {
"MyProp" : ["dolor", "sit"]
}
}
This will effectively replace the MyProp array in the specified document.
If you want to go the bulk route, you don't need scripting to achieve what you want:
POST index/type/_bulk
{ "update" : {"_id" : "1"} }
{ "doc" : {"MyProp" : ["dolor", "sit"] } }
{ "update" : {"_id" : "2"} }
{ "doc" : {"MyProp" : ["dolor", "sit"] } }

Answer 2

Would a _bulk update work for you?
POST test/type1/_bulk
{"update":{"_id":1}}
{"script":{"inline":"ctx._source.MyProp += new_param","params":{"new_param":"bla"},"lang":"groovy"}}
{"update":{"_id":2}}
{"script":{"inline":"ctx._source.MyProp += new_param","params":{"new_param":"bla"},"lang":"groovy"}}
{"update":{"_id":3}}
{"script":{"inline":"ctx._source.MyProp += new_param","params":{"new_param":"bla"},"lang":"groovy"}}
....
And you would also need to enable inline scripting for groovy. What the above would do is to add a bla value to the listed documents in MyProp field. Of course, depending on your requirements many other changes can be performed in that script.