OpenSearch/docs/reference/migration/migrate_7_0/indices.asciidoc

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[[breaking_70_indices_changes]]
=== Indices changes

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==== Index creation no longer defaults to five shards
Previous versions of Elasticsearch defaulted to creating five shards per index.
Starting with 7.0.0, the default is now one shard per index.

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==== `:` is no longer allowed in index name

Due to cross-cluster search using `:` to separate a cluster and index name,
index names may no longer contain `:`.

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==== `index.unassigned.node_left.delayed_timeout` may no longer be negative

Negative values were interpreted as zero in earlier versions but are no
longer accepted.

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==== `_flush` and `_force_merge` will no longer refresh

In previous versions issuing a `_flush` or `_force_merge` (with `flush=true`)
had the undocumented side-effect of refreshing the index which made new documents
visible to searches and non-realtime GET operations. From now on these operations
don't have this side-effect anymore. To make documents visible an explicit `_refresh`
call is needed unless the index is refreshed by the internal scheduler.

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==== Limit to the difference between max_size and min_size in NGramTokenFilter and NGramTokenizer

To safeguard against creating too many index terms, the difference between `max_ngram` and
`min_ngram` in `NGramTokenFilter` and `NGramTokenizer` has been limited to 1. This default
limit can be changed with the index setting `index.max_ngram_diff`. Note that if the limit is
exceeded a error is thrown only for new indices. For existing pre-7.0 indices, a deprecation
warning is logged.

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==== Limit to the difference between max_size and min_size in ShingleTokenFilter

To safeguard against creating too many tokens, the difference between `max_shingle_size` and
`min_shingle_size` in `ShingleTokenFilter` has been limited to 3. This default
limit can be changed with the index setting `index.max_shingle_diff`. Note that if the limit is
exceeded a error is thrown only for new indices. For existing pre-7.0 indices, a deprecation
warning is logged.

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==== Document distribution changes

Indices created with version `7.0.0` onwards will have an automatic `index.number_of_routing_shards`
value set. This might change how documents are distributed across shards depending on how many
shards the index has. In order to maintain the exact same distribution as a pre `7.0.0` index, the
`index.number_of_routing_shards` must be set to the `index.number_of_shards` at index creation time.
Note: if the number of routing shards equals the number of shards `_split` operations are not supported.

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==== Skipped background refresh on search idle shards

Shards belonging to an index that does not have an explicit
`index.refresh_interval` configured will  no longer refresh in the background
once the shard becomes "search idle", ie the shard hasn't seen any search
traffic for `index.search.idle.after` seconds (defaults to `30s`). Searches
that access a search idle shard will be "parked" until the next refresh
happens.  Indexing requests with `wait_for_refresh` will also trigger
a background refresh.

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==== Remove deprecated url parameters for Clear Indices Cache API

The following previously deprecated url parameter have been removed:

* `filter` - use `query` instead
* `filter_cache` - use `query` instead
* `request_cache` - use `request` instead
* `field_data` - use `fielddata` instead

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==== `network.breaker.inflight_requests.overhead` increased to 2

Previously the in flight requests circuit breaker considered only the raw byte representation.
By bumping the value of `network.breaker.inflight_requests.overhead` from 1 to 2, this circuit
breaker considers now also the memory overhead of representing the request as a structured object.

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==== Parent circuit breaker changes

The parent circuit breaker defines a new setting `indices.breaker.total.use_real_memory` which is
`true` by default. This means that the parent circuit breaker will trip based on currently used
heap memory instead of only considering the reserved memory by child circuit breakers. When this
setting is `true`, the default parent breaker limit also changes from 70% to 95% of the JVM heap size.
The previous behavior can be restored by setting `indices.breaker.total.use_real_memory` to `false`.

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==== `fix` value for `index.shard.check_on_startup` is removed

Deprecated option value `fix` for setting `index.shard.check_on_startup` is not supported.

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==== `elasticsearch-translog` is removed

Use the `elasticsearch-shard` tool to remove corrupted translog data.