OpenSearch/docs/reference/index-modules.asciidoc

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[[index-modules]]
= Index Modules
[partintro]
--
Index Modules are modules created per index and control all aspects related to
an index.
[float]
[[index-modules-settings]]
== Index Settings
Index level settings can be set per-index. Settings may be:
_static_::
They can only be set at index creation time or on a
<<indices-open-close,closed index>>.
_dynamic_::
They can be changed on a live index using the
<<indices-update-settings,update-index-settings>> API.
WARNING: Changing static or dynamic index settings on a closed index could
result in incorrect settings that are impossible to rectify without deleting
and recreating the index.
[float]
=== Static index settings
Below is a list of all _static_ index settings that are not associated with any
specific index module:
`index.number_of_shards`::
The number of primary shards that an index should have. Defaults to 5.
This setting can only be set at index creation time. It cannot be
changed on a closed index. Note: the number of shards are limited to `1024` per
index. This limitation is a safety limit to prevent accidental creation of indices
that can destabilize a cluster due to resource allocation. The limit can be modified
by specifying `export ES_JAVA_OPTS="-Des.index.max_number_of_shards=128"` system property on every node that is
part of the cluster.
`index.shard.check_on_startup`::
+
--
experimental[] Whether or not shards should be checked for corruption before opening. When
corruption is detected, it will prevent the shard from being opened. Accepts:
`false`::
(default) Don't check for corruption when opening a shard.
`checksum`::
Check for physical corruption.
`true`::
Check for both physical and logical corruption. This is much more
expensive in terms of CPU and memory usage.
`fix`::
Check for both physical and logical corruption. Segments that were reported
as corrupted will be automatically removed. This option *may result in data loss*.
Use with extreme caution!
Checking shards may take a lot of time on large indices.
--
[[index-codec]] `index.codec`::
The +default+ value compresses stored data with LZ4
compression, but this can be set to +best_compression+
which uses https://en.wikipedia.org/wiki/DEFLATE[DEFLATE] for a higher
compression ratio, at the expense of slower stored fields performance.
[float]
[[dynamic-index-settings]]
=== Dynamic index settings
Below is a list of all _dynamic_ index settings that are not associated with any
specific index module:
`index.number_of_replicas`::
The number of replicas each primary shard has. Defaults to 1.
`index.auto_expand_replicas`::
Auto-expand the number of replicas based on the number of available nodes.
Set to a dash delimited lower and upper bound (e.g. `0-5`) or use `all`
for the upper bound (e.g. `0-all`). Defaults to `false` (i.e. disabled).
`index.refresh_interval`::
How often to perform a refresh operation, which makes recent changes to the
index visible to search. Defaults to `1s`. Can be set to `-1` to disable
refresh.
`index.max_result_window`::
The maximum value of `from + size` for searches to this index. Defaults to
`10000`. Search requests take heap memory and time proportional to
`from + size` and this limits that memory. See
<<search-request-scroll,Scroll>> or <<search-request-search-after,Search After>> for a more efficient alternative
to raising this.
`index.max_rescore_window`::
The maximum value of `window_size` for `rescore`s in searches of this index.
Defaults to `index.max_result_window` which defaults to `10000`. Search
requests take heap memory and time proportional to
`max(window_size, from + size)` and this limits that memory.
`index.blocks.read_only`::
Set to `true` to make the index and index metadata read only, `false` to
allow writes and metadata changes.
`index.blocks.read`::
Set to `true` to disable read operations against the index.
`index.blocks.write`::
Set to `true` to disable write operations against the index.
`index.blocks.metadata`::
Set to `true` to disable index metadata reads and writes.
`index.max_refresh_listeners`::
Maximum number of refresh listeners available on each shard of the index.
These listeners are used to implement <<docs-refresh,`refresh=wait_for`>>.
[float]
=== Settings in other index modules
Other index settings are available in index modules:
<<analysis,Analysis>>::
Settings to define analyzers, tokenizers, token filters and character
filters.
<<index-modules-allocation,Index shard allocation>>::
Control over where, when, and how shards are allocated to nodes.
<<index-modules-mapper,Mapping>>::
Enable or disable dynamic mapping for an index.
<<index-modules-merge,Merging>>::
Control over how shards are merged by the background merge process.
<<index-modules-similarity,Similarities>>::
Configure custom similarity settings to customize how search results are
scored.
<<index-modules-slowlog,Slowlog>>::
Control over how slow queries and fetch requests are logged.
<<index-modules-store,Store>>::
Configure the type of filesystem used to access shard data.
<<index-modules-translog,Translog>>::
Control over the transaction log and background flush operations.
--
include::index-modules/analysis.asciidoc[]
include::index-modules/allocation.asciidoc[]
include::index-modules/mapper.asciidoc[]
include::index-modules/merge.asciidoc[]
include::index-modules/similarity.asciidoc[]
include::index-modules/slowlog.asciidoc[]
include::index-modules/store.asciidoc[]
include::index-modules/translog.asciidoc[]