--
:api: reindex
:request: ReindexRequest
:response: BulkByScrollResponse
--

[id="{upid}-{api}"]
=== Reindex API

[id="{upid}-{api}-request"]
==== Reindex Request

A +{request}+ can be used to copy documents from one or more indexes into a
destination index.

It requires an existing source index and a target index which may or may not exist pre-request. Reindex does not attempt
to set up the destination index. It does not copy the settings of the source index. You should set up the destination
index prior to running a _reindex action, including setting up mappings, shard counts, replicas, etc.

The simplest form of a +{request}+ looks like this:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request]
--------------------------------------------------
<1> Creates the +{request}+
<2> Adds a list of sources to copy from
<3> Adds the destination index

The `dest` element can be configured like the index API to control optimistic concurrency control. Just leaving out
`versionType` (as above) or setting it to internal will cause Elasticsearch to blindly dump documents into the target.
Setting `versionType` to external will cause Elasticsearch to preserve the version from the source, create any documents
that are missing, and update any documents that have an older version in the destination index than they do in the
source index.

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request-versionType]
--------------------------------------------------
<1> Set the versionType to `EXTERNAL`

Setting `opType` to `create` will cause `_reindex` to only create missing documents in the target index. All existing
documents will cause a version conflict. The default `opType` is `index`.

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request-opType]
--------------------------------------------------
<1> Set the opType to `create`

By default version conflicts abort the `_reindex` process but you can just count
them instead with:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request-conflicts]
--------------------------------------------------
<1> Set `proceed` on version conflict

You can limit the documents by adding a query.

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request-query]
--------------------------------------------------
<1> Only copy documents which have field `user` set to `kimchy`

It’s also possible to limit the number of processed documents by setting `maxDocs`.

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request-maxDocs]
--------------------------------------------------
<1> Only copy 10 documents

By default `_reindex` uses batches of 1000. You can change the batch size with `sourceBatchSize`.

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request-sourceSize]
--------------------------------------------------
<1> Use batches of 100 documents

Reindex can also use the ingest feature by specifying a `pipeline`.

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request-pipeline]
--------------------------------------------------
<1> set pipeline to `my_pipeline`

+{request}+ also supports a `script` that modifies the document. It allows you to
also change the document's metadata. The following example illustrates that.

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request-script]
--------------------------------------------------
<1> `setScript` to increment the `likes` field on all documents with user `kimchy`.

+{request}+ supports reindexing from a remote Elasticsearch cluster. When using a remote cluster the query should be
specified inside the `RemoteInfo` object and not using `setSourceQuery`. If both the remote info and the source query are
set it results in a validation error during the request. The reason for this is that the remote Elasticsearch may not
understand queries built by the modern query builders. The remote cluster support works all the way back to Elasticsearch
0.90 and the query language has changed since then. When reaching older versions, it is safer to write the query by hand
in JSON.

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request-remote]
--------------------------------------------------
<1> set remote elastic cluster

+{request}+ also helps in automatically parallelizing using `sliced-scroll` to
slice on `_id`. Use `setSlices` to specify the number of slices to use.

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request-slices]
--------------------------------------------------
<1> set number of slices to use

+{request}+ uses the `scroll` parameter to control how long it keeps the
"search context" alive.
["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request-scroll]
--------------------------------------------------
<1> set scroll time


==== Optional arguments
In addition to the options above the following arguments can optionally be also provided:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request-timeout]
--------------------------------------------------
<1> Timeout to wait for the reindex request to be performed as a `TimeValue`

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-request-refresh]
--------------------------------------------------
<1> Refresh index after calling reindex

include::../execution.asciidoc[]

[id="{upid}-{api}-task-submission"]
==== Reindex task submission
It is also possible to submit a +{request}+ and not wait for it completion with the use of Task API. This is an equivalent of a REST request
with wait_for_completion flag set to false.

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{hlrc-tests}/ReindexIT.java[submit-reindex-task]
--------------------------------------------------
<1> A +{request}+ is constructed the same way as for the synchronous method
<2> A submit method returns a `TaskSubmissionResponse` which contains a task identifier.
<3> The task identifier can be used to get `response` from a completed task.

[id="{upid}-{api}-response"]
==== Reindex Response

The returned +{response}+ contains information about the executed operations and
allows to iterate over each result as follows:

["source","java",subs="attributes,callouts,macros"]
--------------------------------------------------
include-tagged::{doc-tests-file}[{api}-response]
--------------------------------------------------
<1> Get total time taken
<2> Check if the request timed out
<3> Get total number of docs processed
<4> Number of docs that were updated
<5> Number of docs that were created
<6> Number of docs that were deleted
<7> Number of batches that were executed
<8> Number of skipped docs
<9> Number of version conflicts
<10> Number of times request had to retry bulk index operations
<11> Number of times request had to retry search operations
<12> The total time this request has throttled itself not including the current throttle time if it is currently sleeping
<13> Remaining delay of any current throttle sleep or 0 if not sleeping
<14> Failures during search phase
<15> Failures during bulk index operation
