[[docs-update]]
== Update API

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:

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

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

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

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

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

We can also add a new field to the document:

[source,js]
--------------------------------------------------
curl -XPOST 'localhost:9200/test/type1/1/_update' -d '{
    "script" : "ctx._source.text = \"some text\""
}'
--------------------------------------------------

We can also remove a field from the document:

[source,js]
--------------------------------------------------
curl -XPOST 'localhost:9200/test/type1/1/_update' -d '{
    "script" : "ctx._source.remove(\"text\")"
}'
--------------------------------------------------

And, we can delete the doc if the tags contain blue, or ignore (noop):

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

*Note*: Be aware of MVEL and handling of ternary operators and
assignments. Assignment operations have lower precedence than the
ternary operator. Compare the following statements:

[source,js]
--------------------------------------------------
// Will NOT update the tags array
ctx._source.tags.contains(tag) ? ctx.op = \"none\" : ctx._source.tags += tag
// Will update
ctx._source.tags.contains(tag) ? (ctx.op = \"none\") : ctx._source.tags += tag
// Also works
if (ctx._source.tags.contains(tag)) { ctx.op = \"none\" } else { ctx._source.tags += tag }
--------------------------------------------------

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:

[source,js]
--------------------------------------------------
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.

There is also support for `upsert`. If the document does
not already exists, the content of the `upsert` element will be used to
index the fresh doc:

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

Last it also supports `doc_as_upsert`. So that the
provided document will be inserted if the document does not already
exist. This will reduce the amount of data that needs to be sent to
elasticsearch.

[source,js]
--------------------------------------------------
curl -XPOST 'localhost:9200/test/type1/1/_update' -d '{
    "doc" : {
        "name" : "new_name"
    },
    "doc_as_upsert" : true
}'
--------------------------------------------------

The update operation supports similar parameters as the index API,
including:

[horizontal]
`routing`::     Sets the routing that will be used to route the 
                document to the relevant shard.

`parent`::      Simply sets the routing.

`timeout`::     Timeout waiting for a shard to become available.

`replication`:: The replication type for the delete/index operation
                (sync or async).

`consistency`:: The write consistency of the index/delete operation.

`refresh`::     Refresh the index immediately after the operation occurs,
                so that the updated document appears in search results 
                immediately.

`fields`::      return the relevant fields from the updated document.
                Support `_source` to return the full updated 
                source.

                
And also support `retry_on_conflict` which controls how many times to
retry if there is a version conflict between getting the document and
indexing / deleting it. Defaults to `0`.

It also allows to update the `ttl` of a document using `ctx._ttl` and
timestamp using `ctx._timestamp`. Note that if the timestamp is not
updated and not extracted from the `_source` it will be set to the
update date.
