Index API
editIndex API
editThe 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 _doc
with an id of 1:
PUT twitter/_doc/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" : "_doc", "_id" : "1", "_version" : 1, "_seq_no" : 0, "_primary_term" : 1, "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.
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
editThe index operation automatically creates an index if it does not already exist, and applies any index templates that are configured. The index operation also creates a dynamic type mapping for the specified type if one does not already exist. By default, new fields and objects will automatically be added to the mapping definition for the specified type if needed. Check out the mapping section for more information on mapping definitions, and the the put mapping API for information about updating type mappings manually.
Automatic index creation is controlled by the action.auto_create_index
setting. This setting defaults to true
, meaning that indices are always
automatically created. Automatic index creation can be permitted only for
indices matching certain patterns by changing the value of this setting to a
comma-separated list of these patterns. It can also be explicitly permitted and
forbidden by prefixing patterns in the list with a +
or -
. Finally it can
be completely disabled by changing this setting to false
.
PUT _cluster/settings { "persistent": { "action.auto_create_index": "twitter,index10,-index1*,+ind*" } } PUT _cluster/settings { "persistent": { "action.auto_create_index": "false" } } PUT _cluster/settings { "persistent": { "action.auto_create_index": "true" } }
Permit only the auto-creation of indices called |
|
Completely disable the auto-creation of indices. |
|
Permit the auto-creation of indices with any name. This is the default. |
Versioning
editEach 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/_doc/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.
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
editNext 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
orexternal_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
editThe 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/_doc/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/_doc/1/_create { "user" : "kimchy", "post_date" : "2009-11-15T14:12:12", "message" : "trying out Elasticsearch" }
Automatic ID Generation
editThe 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/_doc/ { "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" : "_doc", "_id" : "W0tpsmIBdwcYyG50zbta", "_version" : 1, "_seq_no" : 0, "_primary_term" : 1, "result": "created" }
Routing
editBy 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/_doc?routing=kimchy { "user" : "kimchy", "post_date" : "2009-11-15T14:12:12", "message" : "trying out Elasticsearch" }
In the example above, the "_doc" 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.
Distributed
editThe 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
editTo 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
editControl when the changes made by this request are visible to search. See refresh.
Noop Updates
editWhen 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
editThe 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/_doc/1?timeout=5m { "user" : "kimchy", "post_date" : "2009-11-15T14:12:12", "message" : "trying out Elasticsearch" }