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Elastic Docs ›Elasticsearch Guide [7.10] ›ILM: Manage the index lifecycle ›Index lifecycle actions

Force merge

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Force merge

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Phases allowed: hot, warm.

Force merges the index into the specified maximum number of segments.

This action makes the index read-only.

To use the forcemerge action in the hot phase, the rollover action must be present. If no rollover action is configured, ILM will reject the policy.

The forcemerge action is best effort. It might happen that some of the shards are relocating, in which case they will not be merged.

Options

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max_num_segments
(Required, integer) Number of segments to merge to. To fully merge the index, set to 1.
index_codec

(Optional, string) Codec used to compress the document store. The only accepted value is best_compression, which uses DEFLATE for a higher compression ratio but slower stored fields performance. To use the default LZ4 codec, omit this argument.

If using best_compression, ILM will close and then re-open the index prior to the force merge. While closed, the index will be unavailable for read or write operations.

Example

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PUT _ilm/policy/my_policy
{
  "policy": {
    "phases": {
      "warm": {
        "actions": {
          "forcemerge" : {
            "max_num_segments": 1
          }
        }
      }
    }
  }
}
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