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

[float]
[[breaking_70_indices_changes]]
=== Indices changes

//NOTE: The notable-breaking-changes tagged regions are re-used in the
//Installation and Upgrade Guide

//tag::notable-breaking-changes[]

// end::notable-breaking-changes[]

[float]
==== 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.

[float]
[[_literal_literal_is_no_longer_allowed_in_index_name]]
==== `:` 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 `:`.

[float]
[[index-unassigned-node-left-delayed-timeout-no-longer-negative]]
==== `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.

[float]
[[flush-force-merge-no-longer-refresh]]
==== `_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.

[float]
==== 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.

[float]
==== Limit to the difference between max_shingle_size and min_shingle_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.

[float]
==== 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.

[float]
==== 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.

[float]
==== 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

[float]
[[network-breaker-inflight-requests-overhead-increased-to-2]]
==== `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.

[float]
==== 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`.

[float]
==== Field data circuit breaker changes
As doc values have been enabled by default in earlier versions of Elasticsearch,
there is less need for fielddata. Therefore, the default value of the setting
`indices.breaker.fielddata.limit` has been lowered from 60% to 40% of the JVM
heap size.

[float]
[[fix-value-for-index-shard-check-on-startup-removed]]
==== `fix` value for `index.shard.check_on_startup` is removed

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

[float]
[[elasticsearch-translog-removed]]
==== `elasticsearch-translog` is removed

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