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Index Modules

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Index Modules

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Index Modules are modules created per index and control all aspects related to an index.

Index Settings

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Index level settings can be set per-index. Settings may be:

static: They can only be set at index creation time or on a closed index.
dynamic: They can be changed on a live index using the update-index-settings API.

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.

Static index settings

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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: 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!

Expert only. Checking shards may take a lot of time on large indices.
index.codec: The default value compresses stored data with LZ4 compression, but this can be set to best_compression which uses DEFLATE for a higher compression ratio, at the expense of slower stored fields performance. If you are updating the compression type, the new one will be applied after segments are merged. Segment merging can be forced using force merge.
index.routing_partition_size: The number of shards a custom routing value can go to. Defaults to 1 and can only be set at index creation time. This value must be less than the index.number_of_shards unless the index.number_of_shards value is also 1. See Routing to an index partition for more details about how this setting is used.
index.load_fixed_bitset_filters_eagerly: Indicates whether cached filters are pre-loaded for nested queries. Possible values are true (default) and false.

Dynamic index settings

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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 data nodes in the cluster. 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). Note that the auto-expanded number of replicas does not take any other allocation rules into account, such as shard allocation awareness, filtering or total shards per node, and this can lead to the cluster health becoming YELLOW if the applicable rules prevent all the replicas from being allocated.

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 Scroll or Search After for a more efficient alternative to raising this.

index.max_inner_result_window

The maximum value of from + size for inner hits definition and top hits aggregations to this index. Defaults to 100. Inner hits and top hits aggregation take heap memory and time proportional to from + size and this limits that memory.

index.max_rescore_window

The maximum value of window_size for rescore requests 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.max_docvalue_fields_search

The maximum number of docvalue_fields that are allowed in a query. Defaults to 100. Doc-value fields are costly since they might incur a per-field per-document seek.

index.max_script_fields

The maximum number of script_fields that are allowed in a query. Defaults to 32.

index.max_ngram_diff

The maximum allowed difference between min_gram and max_gram for NGramTokenizer and NGramTokenFilter. Defaults to 1.

index.max_shingle_diff

The maximum allowed difference between max_shingle_size and min_shingle_size for ShingleTokenFilter. Defaults to 3.

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_only_allow_delete

Identical to index.blocks.read_only but allows deleting the index to free up resources.

index.blocks.read

Set to true to disable read operations against the index.

index.blocks.write

Set to true to disable data write operations against the index. Unlike read_only, this setting does not affect metadata. For instance, you can close an index with a write block, but not an index with a read_only block.

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 refresh=wait_for.

index.highlight.max_analyzed_offset

The maximum number of characters that will be analyzed for a highlight request. This setting is only applicable when highlighting is requested on a text that was indexed without offsets or term vectors. By default this settings is unset in 6.x, defaults to -1.

index.max_terms_count

The maximum number of terms that can be used in Terms Query. Defaults to 65536.

index.routing.allocation.enable

Controls shard allocation for this index. It can be set to:

all (default) - Allows shard allocation for all shards.
primaries - Allows shard allocation only for primary shards.
new_primaries - Allows shard allocation only for newly-created primary shards.
none - No shard allocation is allowed.

index.routing.rebalance.enable

Enables shard rebalancing for this index. It can be set to:

all (default) - Allows shard rebalancing for all shards.
primaries - Allows shard rebalancing only for primary shards.
replicas - Allows shard rebalancing only for replica shards.
none - No shard rebalancing is allowed.

index.gc_deletes

The length of time that a deleted document’s version number remains available for further versioned operations. Defaults to 60s.

index.max_regex_length

The maximum length of regex that can be used in Regexp Query. Defaults to 1000.

Settings in other index modules

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Other index settings are available in index modules:

Analysis: Settings to define analyzers, tokenizers, token filters and character filters.
Index shard allocation: Control over where, when, and how shards are allocated to nodes.
Mapping: Enable or disable dynamic mapping for an index.
Merging: Control over how shards are merged by the background merge process.
Similarities: Configure custom similarity settings to customize how search results are scored.
Slowlog: Control over how slow queries and fetch requests are logged.
Store: Configure the type of filesystem used to access shard data.
Translog: Control over the transaction log and background flush operations.

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