text: # Changes in Elastic 5.0
  
  ## Enforce context.Context in PerformRequest and Do
  
  We enforce the usage of `context.Context` everywhere you execute a request.
  You need to change all your `Do()` calls to pass a context: `Do(ctx)`.
  This enables automatic request cancelation and many other patterns.
  
  If you don't need this, simply pass `context.TODO()` or `context.Background()`.
  
  ## Warmers removed
  
  Warmers are no longer necessary and have been [removed in ES 5.0](https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking_50_index_apis.html#_warmers).
  
  ## Optimize removed
  
  Optimize was deprecated in ES 2.0 and has been [removed in ES 5.0](https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking_50_rest_api_changes.html#_literal__optimize_literal_endpoint_removed).
  Use [Force Merge](https://www.elastic.co/guide/en/elasticsearch/reference/master/indices-forcemerge.html) instead.
  
  ## Missing Query removed
  
  The `missing` query has been [removed](https://www.elastic.co/guide/en/elasticsearch/reference/master/query-dsl-exists-query.html#_literal_missing_literal_query).
  Use `exists` query with `must_not` in `bool` query instead.
  
  ## And Query removed
  
  The `and` query has been [removed](https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking_50_search_changes.html#_deprecated_queries_removed).
  Use `must` clauses in a `bool` query instead.
  
  ## Not Query removed
  
  TODO Is it removed?
  
  ## Or Query removed
  
  The `or` query has been [removed](https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking_50_search_changes.html#_deprecated_queries_removed).
  Use `should` clauses in a `bool` query instead.
  
  ## Filtered Query removed
  
  The `filtered` query has been [removed](https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking_50_search_changes.html#_deprecated_queries_removed).
  Use `bool` query instead, which supports `filter` clauses too.
  
  ## Limit Query removed
  
  The `limit` query has been [removed](https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking_50_search_changes.html#_deprecated_queries_removed).
  Use the `terminate_after` parameter instead.
  
  # Template Query removed
  
  The `template` query has been [deprecated](https://www.elastic.co/guide/en/elasticsearch/reference/5.x/query-dsl-template-query.html). You should use
  Search Templates instead.
  
  We remove it from Elastic 5.0 as the 5.0 update is already a good opportunity
  to get rid of old stuff.
  
  ## `_timestamp` and `_ttl` removed
  
  Both of these fields were deprecated and are now [removed](https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking_50_mapping_changes.html#_literal__timestamp_literal_and_literal__ttl_literal).
  
  ## Search template Put/Delete API returns `acknowledged` only
  
  The response type for Put/Delete search templates has changed.
  It only returns a single `acknowledged` flag now.
  
  ## Fields has been renamed to Stored Fields
  
  The `fields` parameter has been renamed to `stored_fields`.
  See [here](https://www.elastic.co/guide/en/elasticsearch/reference/5.x/breaking_50_search_changes.html#_literal_fields_literal_parameter).
  
  ## Fielddatafields has been renamed to Docvaluefields
  
  The `fielddata_fields` parameter [has been renamed](https://www.elastic.co/guide/en/elasticsearch/reference/5.x/breaking_50_search_changes.html#_literal_fielddata_fields_literal_parameter)
  to `docvalue_fields`.
  
  ## Type exists endpoint changed
  
  The endpoint for checking whether a type exists has been changed from
  `HEAD {index}/{type}` to `HEAD {index}/_mapping/{type}`.
  See [here](https://www.elastic.co/guide/en/elasticsearch/reference/5.0/breaking_50_rest_api_changes.html#_literal_head_index_type_literal_replaced_with_literal_head_index__mapping_type_literal).
  
  ## Refresh parameter changed
  
  The `?refresh` parameter previously could be a boolean value. It indicated
  whether changes made by a request (e.g. by the Bulk API) should be immediately
  visible in search, or not. Using `refresh=true` had the positive effect of
  immediately seeing the changes when searching; the negative effect is that
  it is a rather big performance hit.
  
  With 5.0, you now have the choice between these 3 values.
  
  * `"true"` - Refresh immediately
  * `"false"` - Do not refresh (the default value)
  * `"wait_for"` - Wait until ES made the document visible in search
  
  See [?refresh](https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-refresh.html) in the documentation.
  
  Notice that `true` and `false` (the boolean values) are no longer available
  now in Elastic. You must use a string instead, with one of the above values.
  
  ## ReindexerService removed
  
  The `ReindexerService` was a custom solution that was started in the ES 1.x era
  to automate reindexing data, from one index to another or even between clusters.
  
  ES 2.3 introduced its own [Reindex API](https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-reindex.html)
  so we're going to remove our custom solution and ask you to use the native reindexer.
  
  The `ReindexService` is available via `client.Reindex()` (which used to point
  to the custom reindexer).
  
  ## Delete By Query back in core
  
  The [Delete By Query API](https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-delete-by-query.html)
  was moved into a plugin in 2.0. Now its back in core with a complete rewrite based on the Bulk API.
  
  It has it's own endpoint at `/_delete_by_query`.
  
  Delete By Query, Reindex, and Update By Query are very similar under the hood.
  
  ## Reindex, Delete By Query, and Update By Query response changed
  
  The response from the above APIs changed a bit. E.g. the `retries` value
  used to be an `int64` and returns separate values for `bulk` and `search` now:
  
  ```
  // Old
  {
      ...
      "retries": 123,
      ...
  }
  ```
  
  ```
  // New
  {
      ...
      "retries": {
          "bulk": 123,
          "search": 0
      },
      ...
  }
  ```
  
  ## ScanService removed
  
  The `ScanService` is removed. Use the (new) `ScrollService` instead.
  
  ## New ScrollService
  
  There was confusion around `ScanService` and `ScrollService` doing basically
  the same. One was returning slices and didn't support all query details, the
  other returned one document after another and wasn't safe for concurrent use.
  So we merged the two and merged it into a new `ScrollService` that
  removes all the problems with the older services.
  
  In other words:
  If you used `ScanService`, switch to `ScrollService`.
  If you used the old `ScrollService`, you might need to fix some things but
  overall it should just work.
  
  Changes:
  - We replaced `elastic.EOS` with `io.EOF` to indicate the "end of scroll".
  
  TODO Not implemented yet
  
  ## Suggesters
  
  They have been [completely rewritten in ES 5.0](https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking_50_suggester.html).
  
  Some changes:
  - Suggesters no longer have an [output](https://www.elastic.co/guide/en/elasticsearch/reference/master/breaking_50_suggester.html#_simpler_completion_indexing).
  
  TODO Fix all structural changes in suggesters
  
  ## Percolator
  
  Percolator has [changed considerably](https://www.elastic.co/guide/en/elasticsearch/reference/5.x/breaking_50_percolator.html).
  
  Elastic 5.0 adds the new
  [Percolator Query](https://www.elastic.co/guide/en/elasticsearch/reference/5.x/query-dsl-percolate-query.html)
  which can be used in combination with the new
  [Percolator type](https://www.elastic.co/guide/en/elasticsearch/reference/5.x/percolator.html).
  
  The Percolate service is removed from Elastic 5.0.
  
  ## Remove Consistency, add WaitForActiveShards
  
  The `consistency` parameter has been removed in a lot of places, e.g. the Bulk,
  Index, Delete, Delete-by-Query, Reindex, Update, and Update-by-Query API.
  
  It has been replaced by a somewhat similar `wait_for_active_shards` parameter.
  See https://github.com/elastic/elasticsearch/pull/19454.
  