Split an index

Auth

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 number of primary shards in the target index must be a divisor of the source index's index.number_of_routing_shards.
  • 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 · default: 30s

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 · default: 30s

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 union oneOf · default: 1

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: all index-setting

Request body

aliases map string to object

Aliases for the resulting index.

<string> object
filter {} Query

Query used to limit documents the alias can access.

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 · default: false

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

is_write_index boolean · default: false

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

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 map string to object

Configuration options for the target index.

Response

application/json
acknowledged boolean required
shards_acknowledged boolean required
index string required