opensearch-docs-cn/_im-plugin/index-settings.md

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Index settings

You can specify index settings at index creation. There are two types of index settings:

• Static index settings are settings that you cannot update while the index is open. To update a static setting, you must close the index, update the setting, and then reopen the index.
• Dynamic index settings are settings that you can update at any time.

Specifying a setting when creating an index

When creating an index, you can specify its static or dynamic settings as follows:

PUT /testindex
{
  "settings": {
    "index.number_of_shards": 1,
    "index.number_of_replicas": 2
  }
}

{% include copy-curl.html %}

Static index settings

The following table lists all available static index settings.

Setting	Description
index.number_of_shards	The number of primary shards in the index. Default is 1.
index.number_of_routing_shards	The number of routing shards used to split an index.
index.shard.check_on_startup	Whether the index's shards should be checked for corruption. Available options are false (do not check for corruption), checksum (check for physical corruption), and true (check for both physical and logical corruption). Default is false.
index.codec	Determines how the index’s stored fields are compressed and stored on disk. This setting impacts the size of the index shards and the performance of the index operations. Valid values are: - default - best_compression - zstd (OpenSearch 2.9 and later) - zstd_no_dict(OpenSearch 2.9 and later). For zstd and zstd_no_dict, you can specify the compression level in the index.codec.compression_level setting. For more information, see Index codec settings. Optional. Default is default.
index.codec.compression_level	The compression level setting provides a tradeoff between compression ratio and speed. A higher compression level results in a higher compression ratio (smaller storage size) with a tradeoff in speed (slower compression and decompression speeds lead to greater indexing and search latencies). Can only be specified if index.codec is set to zstd and zstd_no_dict compression levels in OpenSearch 2.9 and later. Valid values are integers in the [1, 6] range. For more information, see Index codec settings. Optional. Default is 3.
index.routing_partition_size	The number of shards a custom routing value can go to. Routing helps an imbalanced cluster by relocating values to a subset of shards rather than a single shard. To enable routing, set this value to greater than 1 but less than index.number_of_shards. Default is 1.
index.soft_deletes.retention_lease.period	The maximum amount of time to retain a shard's history of operations. Default is 12h.
index.load_fixed_bitset_filters_eagerly	Whether OpenSearch should preload cached filters. Available options are true and false. Default is true.
index.hidden	Whether the index should be hidden. Hidden indexes are not returned as part of queries that have wildcards. Available options are true and false. Default is false.
index.merge.policy	This setting controls the merge policy for the Lucene segments. The available options are tiered and log_byte_size. The default is tiered, but for time-series data, such as log events, we recommend that you use the log_byte_size merge policy, which can improve query performance when conducting range queries on the @timestamp field. We recommend that you not change the merge policy of an existing index. Instead, configure this setting when creating a new index.

Updating a static index setting

You can update a static index setting only on a closed index. The following example demonstrates updating the index codec setting.

First, close an index:

POST /testindex/_close

{% include copy-curl.html %}

Then update the settings by sending a request to the _settings endpoint:

PUT /testindex/_settings
{
  "index": {
    "codec": "zstd_no_dict",
    "codec.compression_level": 3
  }
}

{% include copy-curl.html %}

Last, reopen the index to enable read and write operations:

POST /testindex/_open

{% include copy-curl.html %}

For more information about updating settings, including supported query parameters, see Update settings.

Dynamic index settings

The following table lists all available dynamic index settings.

Setting	Description
index.number_of_replicas	The number of replica shards each primary shard should have. For example, if you have 4 primary shards and set index.number_of_replicas to 3, the index has 12 replica shards. Default is 1.
index.auto_expand_replicas	Whether the cluster should automatically add replica shards based on the number of data nodes. Specify a lower bound and upper limit (for example, 0--9) or all for the upper limit. For example, if you have 5 data nodes and set index.auto_expand_replicas to 0--3, then the cluster does not automatically add another replica shard. However, if you set this value to 0-all and add 2 more nodes for a total of 7, the cluster will expand to now have 6 replica shards. Default is disabled.
index.search.idle.after	The amount of time a shard should wait for a search or get request until it goes idle. Default is 30s.
index.refresh_interval	How often the index should refresh, which publishes its most recent changes and makes them available for searching. Can be set to -1 to disable refreshing. Default is 1s.
index.max_result_window	The maximum value of from + size for searches of the index. from is the starting index to search from, and size is the number of results to return. Default is 10000.
index.max_inner_result_window	The maximum value of from + size that specifies the number of returned nested search hits and most relevant document aggregated during the query. from is the starting index to search from, and size is the number of top hits to return. Default is 100.
index.max_rescore_window	The maximum value of window_size for rescore requests to the index. Rescore requests reorder the index's documents and return a new score, which can be more precise. Default is the same as index.max_inner_result_window or 10000 by default.
index.max_docvalue_fields_search	The maximum number of docvalue_fields allowed in a query. Default is 100.
index.max_script_fields	The maximum number of script_fields allowed in a query. Default is 32.
index.max_ngram_diff	The maximum difference between min_gram and max_gram values for the NGramTokenizer and NGramTokenFilter. Default is 1.
index.max_shingle_diff	The maximum difference between max_shingle_size and min_shingle_size to feed into the shingle token filter. Default is 3.
index.max_refresh_listeners	The maximum number of refresh listeners each shard is allowed to have.
index.analyze.max_token_count	The maximum number of tokens that can be returned from the _analyze API operation. Default is 10000.
index.highlight.max_analyzed_offset	The number of characters a highlight request can analyze. Default is 1000000.
index.max_terms_count	The maximum number of terms a terms query can accept. Default is 65536.
index.max_regex_length	The maximum character length of regex that can be in a regexp query. Default is 1000.
index.query.default_field	A field or list of fields that OpenSearch uses in queries in case a field isn't specified in the parameters.
index.routing.allocation.enable	Specifies options for the index’s shard allocation. Available options are all (allow allocation for all shards), primaries (allow allocation only for primary shards), new_primaries (allow allocation only for new primary shards), and none (do not allow allocation). Default is all.
index.routing.rebalance.enable	Enables shard rebalancing for the index. Available options are all (allow rebalancing for all shards), primaries (allow rebalancing only for primary shards), replicas (allow rebalancing only for replicas), and none (do not allow rebalancing). Default is all.
index.gc_deletes	The amount of time to retain a deleted document's version number. Default is 60s.
index.default_pipeline	The default ingest node pipeline for the index. If the default pipeline is set and the pipeline does not exist, then index requests fail. The pipeline name _none specifies that the index does not have an ingest pipeline.
index.final_pipeline	The final ingest node pipeline for the index. If the final pipeline is set and the pipeline does not exist, then index requests fail. The pipeline name _none specifies that the index does not have an ingest pipeline.

Updating a dynamic index setting

You can update a dynamic index setting at any time through the API. For example, to update the refresh interval, use the following request:

PUT /testindex/_settings
{
  "index": {
    "refresh_interval": "2s"
  }
}

{% include copy-curl.html %}

For more information about updating settings, including supported query parameters, see Update settings.