72 lines
2.7 KiB
Plaintext
72 lines
2.7 KiB
Plaintext
[[indices-forcemerge]]
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== Force Merge
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The force merge API allows to force merging of one or more indices through an
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API. The merge relates to the number of segments a Lucene index holds within
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each shard. The force merge operation allows to reduce the number of segments by
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merging them.
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This call will block until the merge is complete. If the http connection is
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lost, the request will continue in the background, and any new requests will
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block until the previous force merge is complete.
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WARNING: Force merge should only be called against *read-only indices*. Running
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force merge against a read-write index can cause very large segments to be produced
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(>5Gb per segment), and the merge policy will never consider it for merging again until
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it mostly consists of deleted docs. This can cause very large segments to remain in the shards.
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[source,js]
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--------------------------------------------------
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POST /twitter/_forcemerge
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--------------------------------------------------
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// CONSOLE
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// TEST[setup:twitter]
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[float]
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[[forcemerge-parameters]]
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=== Request Parameters
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The force merge API accepts the following request parameters:
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[horizontal]
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`max_num_segments`:: The number of segments to merge to. To fully
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merge the index, set it to `1`. Defaults to simply checking if a
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merge needs to execute, and if so, executes it.
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`only_expunge_deletes`:: Should the merge process only expunge segments with
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deletes in it. In Lucene, a document is not deleted from a segment, just marked
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as deleted. During a merge process of segments, a new segment is created that
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does not have those deletes. This flag allows to only merge segments that have
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deletes. Defaults to `false`. Note that this won't override the
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`index.merge.policy.expunge_deletes_allowed` threshold.
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`flush`:: Should a flush be performed after the forced merge. Defaults to
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`true`.
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[source,js]
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--------------------------------------------------
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POST /kimchy/_forcemerge?only_expunge_deletes=false&max_num_segments=100&flush=true
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--------------------------------------------------
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// CONSOLE
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// TEST[s/^/PUT kimchy\n/]
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[float]
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[[forcemerge-multi-index]]
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=== Multi Index
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The force merge API can be applied to more than one index with a single call, or
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even on `_all` the indices. Multi index operations are executed one shard at a
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time per node. Force merge makes the storage for the shard being merged
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temporarily increase, up to double its size in case `max_num_segments` is set
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to `1`, as all segments need to be rewritten into a new one.
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[source,js]
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--------------------------------------------------
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POST /kimchy,elasticsearch/_forcemerge
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POST /_forcemerge
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--------------------------------------------------
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// CONSOLE
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// TEST[s/^/PUT kimchy\nPUT elasticsearch\n/]
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