Split an index Added in 6.1.0

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.

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.

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.

  • timeout string

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

  • 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).

application/json

Body

  • aliases object

    Aliases for the resulting index.

    Hide aliases attribute Show aliases attribute object
  • settings object

    Configuration options for the target index.

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

      Additional properties are allowed.

Responses

POST /{index}/_split/{target} 
curl \
 -X POST http://api.example.com/{index}/_split/{target} \
 -H "Content-Type: application/json" \
 -d '"{\n  \"settings\": {\n    \"index.number_of_shards\": 2\n  }\n}"'
Request example 
{
  "settings": {
    "index.number_of_shards": 2
  }
}
Response examples (200) 
{
  "acknowledged": true,
  "shards_acknowledged": true,
  "index": "string"
}