Index API

The index API adds or updates a typed JSON document in a specific index, making it searchable. The following example inserts the JSON document into the "twitter" index, under a type called "tweet" with an id of 1:

PUT twitter/tweet/1
{
    "user" : "kimchy",
    "post_date" : "2009-11-15T14:12:12",
    "message" : "trying out Elasticsearch"
}

The result of the above index operation is:

{
    "_shards" : {
        "total" : 2,
        "failed" : 0,
        "successful" : 2
    },
    "_index" : "twitter",
    "_type" : "tweet",
    "_id" : "1",
    "_version" : 1,
    "created" : true,
    "result" : created
}

The _shards header provides information about the replication process of the index operation.

  • total - Indicates to how many shard copies (primary and replica shards) the index operation should be executed on.
  • successful- Indicates the number of shard copies the index operation succeeded on.
  • failed - An array that contains replication related errors in the case an index operation failed on a replica shard.

The index operation is successful in the case successful is at least 1.

Note

Replica shards may not all be started when an indexing operation successfully returns (by default, only the primary is required, but this behavior can be changed). In that case, total will be equal to the total shards based on the number_of_replicas setting and successful will be equal to the number of shards started (primary plus replicas). If there were no failures, the failed will be 0.

Automatic Index Creation

The index operation automatically creates an index if it has not been created before (check out the create index API for manually creating an index), and also automatically creates a dynamic type mapping for the specific type if one has not yet been created (check out the put mapping API for manually creating a type mapping).

The mapping itself is very flexible and is schema-free. New fields and objects will automatically be added to the mapping definition of the type specified. Check out the mapping section for more information on mapping definitions.

Automatic index creation can be disabled by setting action.auto_create_index to false in the config file of all nodes. Automatic mapping creation can be disabled by setting index.mapper.dynamic to false per-index as an index setting.

Automatic index creation can include a pattern based white/black list, for example, set action.auto_create_index to +aaa*,-bbb*,+ccc*,-* (+ meaning allowed, and - meaning disallowed).

Versioning

Each indexed document is given a version number. The associated version number is returned as part of the response to the index API request. The index API optionally allows for optimistic concurrency control when the version parameter is specified. This will control the version of the document the operation is intended to be executed against. A good example of a use case for versioning is performing a transactional read-then-update. Specifying a version from the document initially read ensures no changes have happened in the meantime (when reading in order to update, it is recommended to set preference to _primary). For example:

PUT twitter/tweet/1?version=2
{
    "message" : "elasticsearch now has versioning support, double cool!"
}

NOTE: versioning is completely real time, and is not affected by the near real time aspects of search operations. If no version is provided, then the operation is executed without any version checks.

By default, internal versioning is used that starts at 1 and increments with each update, deletes included. Optionally, the version number can be supplemented with an external value (for example, if maintained in a database). To enable this functionality, version_type should be set to external. The value provided must be a numeric, long value greater or equal to 0, and less than around 9.2e+18. When using the external version type, instead of checking for a matching version number, the system checks to see if the version number passed to the index request is greater than the version of the currently stored document. If true, the document will be indexed and the new version number used. If the value provided is less than or equal to the stored document’s version number, a version conflict will occur and the index operation will fail.

Warning

External versioning supports the value 0 as a valid version number. This allows the version to be in sync with an external versioning system where version numbers start from zero instead of one. It has the side effect that documents with version number equal to zero cannot neither be updated using the Update-By-Query API nor be deleted using the Delete By Query API as long as their version number is equal to zero.

A nice side effect is that there is no need to maintain strict ordering of async indexing operations executed as a result of changes to a source database, as long as version numbers from the source database are used. Even the simple case of updating the elasticsearch index using data from a database is simplified if external versioning is used, as only the latest version will be used if the index operations are out of order for whatever reason.

Version types

Next to the internal & external version types explained above, Elasticsearch also supports other types for specific use cases. Here is an overview of the different version types and their semantics.

internal
only index the document if the given version is identical to the version of the stored document.
external or external_gt
only index the document if the given version is strictly higher than the version of the stored document or if there is no existing document. The given version will be used as the new version and will be stored with the new document. The supplied version must be a non-negative long number.
external_gte
only index the document if the given version is equal or higher than the version of the stored document. If there is no existing document the operation will succeed as well. The given version will be used as the new version and will be stored with the new document. The supplied version must be a non-negative long number.

NOTE: The external_gte version type is meant for special use cases and should be used with care. If used incorrectly, it can result in loss of data. There is another option, force, which is deprecated because it can cause primary and replica shards to diverge.

Operation Type

The index operation also accepts an op_type that can be used to force a create operation, allowing for "put-if-absent" behavior. When create is used, the index operation will fail if a document by that id already exists in the index.

Here is an example of using the op_type parameter:

PUT twitter/tweet/1?op_type=create
{
    "user" : "kimchy",
    "post_date" : "2009-11-15T14:12:12",
    "message" : "trying out Elasticsearch"
}

Another option to specify create is to use the following uri:

PUT twitter/tweet/1/_create
{
    "user" : "kimchy",
    "post_date" : "2009-11-15T14:12:12",
    "message" : "trying out Elasticsearch"
}

Automatic ID Generation

The index operation can be executed without specifying the id. In such a case, an id will be generated automatically. In addition, the op_type will automatically be set to create. Here is an example (note the POST used instead of PUT):

POST twitter/tweet/
{
    "user" : "kimchy",
    "post_date" : "2009-11-15T14:12:12",
    "message" : "trying out Elasticsearch"
}

The result of the above index operation is:

{
    "_shards" : {
        "total" : 2,
        "failed" : 0,
        "successful" : 2
    },
    "_index" : "twitter",
    "_type" : "tweet",
    "_id" : "6a8ca01c-7896-48e9-81cc-9f70661fcb32",
    "_version" : 1,
    "created" : true,
    "result": "created"
}

Routing

By default, shard placement — or routing — is controlled by using a hash of the document’s id value. For more explicit control, the value fed into the hash function used by the router can be directly specified on a per-operation basis using the routing parameter. For example:

POST twitter/tweet?routing=kimchy
{
    "user" : "kimchy",
    "post_date" : "2009-11-15T14:12:12",
    "message" : "trying out Elasticsearch"
}

In the example above, the "tweet" document is routed to a shard based on the routing parameter provided: "kimchy".

When setting up explicit mapping, the _routing field can be optionally used to direct the index operation to extract the routing value from the document itself. This does come at the (very minimal) cost of an additional document parsing pass. If the _routing mapping is defined and set to be required, the index operation will fail if no routing value is provided or extracted.

Parents & Children

A child document can be indexed by specifying its parent when indexing. For example:

PUT blogs
{
  "mappings": {
    "tag_parent": {},
    "blog_tag": {
      "_parent": {
        "type": "tag_parent"
      }
    }
  }
}

PUT blogs/blog_tag/1122?parent=1111
{
    "tag" : "something"
}

When indexing a child document, the routing value is automatically set to be the same as its parent, unless the routing value is explicitly specified using the routing parameter.

Distributed

The index operation is directed to the primary shard based on its route (see the Routing section above) and performed on the actual node containing this shard. After the primary shard completes the operation, if needed, the update is distributed to applicable replicas.

Wait For Active Shards

To improve the resiliency of writes to the system, indexing operations can be configured to wait for a certain number of active shard copies before proceeding with the operation. If the requisite number of active shard copies are not available, then the write operation must wait and retry, until either the requisite shard copies have started or a timeout occurs. By default, write operations only wait for the primary shards to be active before proceeding (i.e. wait_for_active_shards=1). This default can be overridden in the index settings dynamically by setting index.write.wait_for_active_shards. To alter this behavior per operation, the wait_for_active_shards request parameter can be used.

Valid values are all or any positive integer up to the total number of configured copies per shard in the index (which is number_of_replicas+1). Specifying a negative value or a number greater than the number of shard copies will throw an error.

For example, suppose we have a cluster of three nodes, A, B, and C and we create an index index with the number of replicas set to 3 (resulting in 4 shard copies, one more copy than there are nodes). If we attempt an indexing operation, by default the operation will only ensure the primary copy of each shard is available before proceeding. This means that even if B and C went down, and A hosted the primary shard copies, the indexing operation would still proceed with only one copy of the data. If wait_for_active_shards is set on the request to 3 (and all 3 nodes are up), then the indexing operation will require 3 active shard copies before proceeding, a requirement which should be met because there are 3 active nodes in the cluster, each one holding a copy of the shard. However, if we set wait_for_active_shards to all (or to 4, which is the same), the indexing operation will not proceed as we do not have all 4 copies of each shard active in the index. The operation will timeout unless a new node is brought up in the cluster to host the fourth copy of the shard.

It is important to note that this setting greatly reduces the chances of the write operation not writing to the requisite number of shard copies, but it does not completely eliminate the possibility, because this check occurs before the write operation commences. Once the write operation is underway, it is still possible for replication to fail on any number of shard copies but still succeed on the primary. The _shards section of the write operation’s response reveals the number of shard copies on which replication succeeded/failed.

{
    "_shards" : {
        "total" : 2,
        "failed" : 0,
        "successful" : 2
    }
}

Refresh

Control when the changes made by this request are visible to search. See refresh.

Noop Updates

When updating a document using the index api a new version of the document is always created even if the document hasn’t changed. If this isn’t acceptable use the _update api with detect_noop set to true. This option isn’t available on the index api because the index api doesn’t fetch the old source and isn’t able to compare it against the new source.

There isn’t a hard and fast rule about when noop updates aren’t acceptable. It’s a combination of lots of factors like how frequently your data source sends updates that are actually noops and how many queries per second elasticsearch runs on the shard with receiving the updates.

Timeout

The primary shard assigned to perform the index operation might not be available when the index operation is executed. Some reasons for this might be that the primary shard is currently recovering from a gateway or undergoing relocation. By default, the index operation will wait on the primary shard to become available for up to 1 minute before failing and responding with an error. The timeout parameter can be used to explicitly specify how long it waits. Here is an example of setting it to 5 minutes:

PUT twitter/tweet/1?timeout=5m
{
    "user" : "kimchy",
    "post_date" : "2009-11-15T14:12:12",
    "message" : "trying out Elasticsearch"
}