OpenSearch/docs/reference/index-modules.asciidoc
Jim Ferenczi aea7660e37 Add search_after parameter in the Search API.
The search_after parameter provides a way to efficiently paginate from one page to the next. This parameter accepts an array of sort values, those values are then used by the searcher to sort the top hits from the first document that is greater to the sort values.
This parameter must be used in conjunction with the sort parameter, it must contain exactly the same number of values than the number of fields to sort on.

NOTE: A field with one unique value per document should be used as the last element of the sort specification. Otherwise the sort order for documents that have the same sort values would be undefined. The recommended way is to use the field `_uuid` which is certain to contain one unique value for each document.

Fixes #8192
2016-01-27 09:42:58 +01:00

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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.
`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`::
experimental[] 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.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.ttl.disable_purge`::
experimental[] Disables the purge of <<mapping-ttl-field,expired docs>> on
the current index.
[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-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/similarity.asciidoc[]
include::index-modules/slowlog.asciidoc[]
include::index-modules/store.asciidoc[]
include::index-modules/translog.asciidoc[]