Split an index Generally available; Added in 6.1.0

POST /{index}/_split/{target}
Api key auth Basic auth Bearer auth

All methods and paths for this operation:

PUT /{index}/_split/{target}

POST /{index}/_split/{target}

Split an index into a new index with more primary shards.

  • Before you can split an index:

  • The index must be read-only.

  • The cluster health status must be green.

You can do make an index read-only with the following request using the add index block API:

PUT /my_source_index/_block/write

The current write index on a data stream cannot be split. In order to split the current write index, the data stream must first be rolled over so that a new write index is created and then the previous write index can be split.

The number of times the index can be split (and the number of shards that each original shard can be split into) is determined by the index.number_of_routing_shards setting. The number of routing shards specifies the hashing space that is used internally to distribute documents across shards with consistent hashing. For instance, a 5 shard index with number_of_routing_shards set to 30 (5 x 2 x 3) could be split by a factor of 2 or 3.

A split operation:

  • Creates a new target index with the same definition as the source index, but with a larger number of primary shards.
  • Hard-links segments from the source index into the target index. If the file system doesn't support hard-linking, all segments are copied into the new index, which is a much more time consuming process.
  • Hashes all documents again, after low level files are created, to delete documents that belong to a different shard.
  • Recovers the target index as though it were a closed index which had just been re-opened.

IMPORTANT: Indices can only be split if they satisfy the following requirements:

  • The target index must not exist.
  • The source index must have fewer primary shards than the target index.
  • The number of primary shards in the target index must be a multiple of the number of primary shards in the source index.
  • The node handling the split process must have sufficient free disk space to accommodate a second copy of the existing index.

Required authorization

  • Index privileges: manage

Path parameters

  • index string Required

    Name of the source index to split.

  • target string Required

    Name of the target index to create.

Query parameters

  • master_timeout string

    Period to wait for a connection to the master node. If no response is received before the timeout expires, the request fails and returns an error.

    External documentation
  • timeout string

    Period to wait for a response. If no response is received before the timeout expires, the request fails and returns an error.

    External documentation
  • wait_for_active_shards number | string

    The number of shard copies that must be active before proceeding with the operation. Set to all or any positive integer up to the total number of shards in the index (number_of_replicas+1).

    Values are all or index-setting.

application/json

Body

  • aliases object

    Aliases for the resulting index.

    Hide aliases attribute Show aliases attribute object
    • * object Additional properties
      Hide * attributes Show * attributes object
      • filter object

        Query used to limit documents the alias can access.

        External documentation
      • index_routing string

        Value used to route indexing operations to a specific shard. If specified, this overwrites the routing value for indexing operations.

      • is_hidden boolean

        If true, the alias is hidden. All indices for the alias must have the same is_hidden value.

        Default value is false.

      • is_write_index boolean

        If true, the index is the write index for the alias.

        Default value is false.

      • routing string

        Value used to route indexing and search operations to a specific shard.

      • search_routing string

        Value used to route search operations to a specific shard. If specified, this overwrites the routing value for search operations.

  • settings object

    Configuration options for the target index.

    Hide settings attribute Show settings attribute object
    • * object Additional properties

Responses

  • 200 application/json
    Hide response attributes Show response attributes object
    • acknowledged boolean Required
    • shards_acknowledged boolean Required
    • index string Required
POST /{index}/_split/{target} 
POST /my-index-000001/_split/split-my-index-000001
{
  "settings": {
    "index.number_of_shards": 2
  }
}
resp = client.indices.split(
    index="my-index-000001",
    target="split-my-index-000001",
    settings={
        "index.number_of_shards": 2
    },
)
const response = await client.indices.split({
  index: "my-index-000001",
  target: "split-my-index-000001",
  settings: {
    "index.number_of_shards": 2,
  },
});
response = client.indices.split(
  index: "my-index-000001",
  target: "split-my-index-000001",
  body: {
    "settings": {
      "index.number_of_shards": 2
    }
  }
)
$resp = $client->indices()->split([
    "index" => "my-index-000001",
    "target" => "split-my-index-000001",
    "body" => [
        "settings" => [
            "index.number_of_shards" => 2,
        ],
    ],
]);
curl -X POST -H "Authorization: ApiKey $ELASTIC_API_KEY" -H "Content-Type: application/json" -d '{"settings":{"index.number_of_shards":2}}' "$ELASTICSEARCH_URL/my-index-000001/_split/split-my-index-000001"
Request example
Split an existing index into a new index with more primary shards. 
{
  "settings": {
    "index.number_of_shards": 2
  }
}