The update API allows to update a document based on a script provided. The operation gets the document (collocated with the shard) from the index, runs the script (with optional script language and parameters), and index back the result (also allows to delete, or ignore the operation). It uses versioning to make sure no updates have happened during the "get" and "reindex".

Note, this operation still means full reindex of the document, it just removes some network roundtrips and reduces chances of version conflicts between the get and the index. The _source field need to be enabled for this feature to work.

For example, lets index a simple doc:

curl -XPUT localhost:9200/test/type1/1-d '{
     "counter":1,"tags":["red"]}'

Scripted updates

Now, we can execute a script that would increment the counter:

curl -XPOST 'localhost:9200/test/type1/1/_update'-d '{
     "script":{
     "inline":"ctx._source.counter += count","params":{
     "count":4}}}'

We can add a tag to the list of tags (note, if the tag exists, it will still add it, since its a list):

curl -XPOST 'localhost:9200/test/type1/1/_update'-d '{
     "script":{
     "inline":"ctx._source.tags += tag","params":{
     "tag":"blue"}}}'

In addition to _source, the following variables are available through the ctx map: _index, _type, _id, _version, _routing, _parent, _timestamp, _ttl.

We can also add a new field to the document:

curl -XPOST 'localhost:9200/test/type1/1/_update'-d '{
     "script":"ctx._source.name_of_new_field = \"value_of_new_field\""}'

Or remove a field from the document:

curl -XPOST 'localhost:9200/test/type1/1/_update'-d '{
     "script":"ctx._source.remove(\"name_of_field\")"}'

And, we can even change the operation that is executed. This example deletes the doc if the tags field contain blue, otherwise it does nothing (noop):

curl -XPOST 'localhost:9200/test/type1/1/_update'-d '{
     "script":{
     "inline":"ctx._source.tags.contains(tag) ? ctx.op = \"delete\" : ctx.op = \"none\"","params":{
     "tag":"blue"}}}'

Updates with a partial document

The update API also support passing a partial document, which will be merged into the existing document (simple recursive merge, inner merging of objects, replacing core "keys/values" and arrays). For example:

curl -XPOST 'localhost:9200/test/type1/1/_update'-d '{
     "doc":{
     "name":"new_name"}}'

If both doc and script is specified, then doc is ignored. Best is to put your field pairs of the partial document in the script itself.

Detecting noop updates

If doc is specified its value is merged with the existing _source. By default the document is only reindexed if the new _source field differs from the old. Setting detect_noop to false will cause Elasticsearch to always update the document even if it hasn’t changed. For example:

curl -XPOST 'localhost:9200/test/type1/1/_update'-d '{
     "doc":{
     "name":"new_name"},"detect_noop":false}'

If name was new_name before the request was sent then document is still reindexed.

Upserts

If the document does not already exist, the contents of the upsert element will be inserted as a new document. If the document does exist, then the script will be executed instead:

curl -XPOST 'localhost:9200/test/type1/1/_update'-d '{
     "script":{
     "inline":"ctx._source.counter += count","params":{
     "count":4}},"upsert":{
     "counter":1}}'

scripted_upsert

If you would like your script to run regardless of whether the document exists or not — i.e. the script handles initializing the document instead of the upsert element — then set scripted_upsert to true:

curl -XPOST 'localhost:9200/sessions/session/dh3sgudg8gsrgl/_update'-d '{
     "scripted_upsert":true,"script":{
     "id":"my_web_session_summariser","params":{
     "pageViewEvent":{
     "url":"foo.com/bar","response":404,"time":"2014-01-01 12:32"}}},"upsert":{}}'

doc_as_upsert

Instead of sending a partial doc plus an upsert doc, setting doc_as_upsert to true will use the contents of doc as the upsert value:

curl -XPOST 'localhost:9200/test/type1/1/_update'-d '{
     "doc":{
     "name":"new_name"},"doc_as_upsert":true}'https://www.elastic.co/guide/en/elasticsearch/reference/2.1/docs-update.html#docs-update