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The Full-text Search Service applies to Optimizely Content Management System (CMS 11) and is not supported on Optimizely Digital Experience Platform (DXP) and other cloud service deployments. It is a legacy feature that will be removed in future versions. **This section is not supported for ASP.NET Core-based applications.**

The Optimizely Full-Text Search Service (FTS Service) is a stand-alone WCF REST Service on top of an unmodified version of the open source search engine [Lucene .NET](🔗) and uses Atom with extensions described in Atom and Extensions as data protocol. The service is deployed through the _EPiServer.Search_ Nuget package. Services are hosted by the IIS and are invoked by the _IndexingService.svc_ file, which means that multiple services can exists within the same environment. One service also can host multiple indexes as described in Named Indexes and Multi-Search. The following image shows a typical setup:

## Assemblies and namespaces

The `EPiServer.Search.IndexingService` assembly contains the following namespaces:

  • `EPiServer.Search.IndexingService` contains core classes for the Optimizely FTS Service, most notably are the `NamedIndex`, `IndexingService`, and `IndexingServiceHandler` classes.

  • `EPiServer.Search.IndexingService.Configuration` contains configuration classes for the Optimizely FTS Service.

  • `EPiServer.Search.IndexingService.Security` contains core classes for client authentication

  • `EPiServer.Search.IndexingService.IndexFieldSerializers` contains core classes for serializing and de-serializing Atom feed items and Lucene Document Fields.

## Service REST API

The Optimizely FTS Service defines the following REST endpoints:

[baseUri]/update/ <br>?accessKey={accessKey}POSTAccepts an Atom feed with feed items to add to the index where:<ul><li><strong>accessKey</strong> is the connecting client access key</li></ul>
[baseUri]/search/ <br>?q={q} <br>&namedindexes={namedindexes} <br>&format=xml <br>&offset={offset} <br>&limit={limit} <br>&accesskey={accesskey}GETReturns an Atom feed with feed items corresponding to hits in the index where: - **q** is the query expression to parse - **namedIndexes** is a pipe separated list of indexes to search -** offset** is the offset from first result item -** limit** is the number of items to return from offset - **accessKey** is the connecting client access key
[baseUri]/reset/ <br>?namedindex={namedindex} <br>&accessKey={accessKey}POSTWipes all content for the passed named index
[baseUri]/namedindexes/ <br>?accesskey={accesskey}GETReturns an Atom feed with items corresponding to the configured named indexes for the service

## Feature highlights

### ReferenceId

When the `ReferenceId` extension contains a value, the Optimizely FTS Service determines that it is not a standalone item, but an item that belongs to another item already in the index, such as comments in Optimizely Community. When a comment is added to the index, the ReferenceId is set to the commented entity and when a query expression matched the contents of the comment, the commented entity returns as the IndexResponseItem and not the comment itself.

Any `IndexRequestItem` with `IndexAction.Add` and with a `ReferenceId` set, is added to the reference index automatically created for all configured indexes with the suffix “\_ref”. The search engine internally finds the parent item corresponding to the `ReferenceId` (by ID) and updates it so that all contents of any items in the “\_ref” index for the parent item is added to the parent item searchable metadata. In this way, there is no need to send all data over and over when updating the entity client side. You cannot search specific fields in reference data because all default searchable fields chunked together and added to the main items metadata.

You cannot update the reference id property for an item after it is added. All items with the `IndexActionUpdate` or `Remove` automatically updates its parent in the index if it was originally added with the reference ID set.

Content in files are indexed, the installed Ifilters decide which files are included.

### DataUri

When the `DataUri` extension contains a value, the Optimizely FTS Service immediately enqueues the whole request (in memory queue). Dequeueing of a `DataUri` request results in a call to the URI where the contents is concatenated to the `IndexRequestItem.DisplayText` and `IndexRequestItem.MetaData`, according to the configured value of `maxDisplayTextLength`.

The Optimizely FTS Service currently only supports File Uri’s and where the file needs to be accessible locally from the service perspective. You can override the behavior by overriding the `GetFileUriContent(Uri)` method and/or `GetNonFileUriContent(Uri)` in the `IndexingServiceHandler`.

### Named indexes and multi-search

The Optimizely FTS Service lets you configure multiple indexes, which you can use where there is an obvious separation of indexed content, or where the there is an existing (Lucene-compatible) index that is updated from a different source. Multiple named indexes need to be configured so that the fields for the index documents maps to the pre-defined field names in the service. See [Configure Optimizely full-text search service (Legacy)](🔗).

When you update the index, the target index (by name) is specified in the NamedIndex attribute extension of the Atom-formatted request. When you search the index, multiple indexes may be specified in the request and the Optimizely FTS Service searches each one of the specified indexes and returns a merged result set. If you do not specify any named index, the default index is used.

### VirtualPath

The `VirtualPath` feature enables structuring of indexed content in a tree structure where you can make searches under a certain tree node. This is accomplished by storing the literal path together with the index document and searching the index with a path with a trailing wildcard. The path always (when updating or searching) includes the full path from the root and up. For example: A document stored with the `VirtualPath` field set to _node1/node2_ would be a valid search result when you search for documents with the path _node1_ or _node1/node2_. However, it is not considered if the path only specified _node2_. If the IndexRequestItem.AutoUpdateVirtualPath attribute is set when you update or remove an item, search uses the VirtualPath to update or remove all items under the provided node.

### Paging

You can page search results at the service or at the client. Default configuration (`useIndexingServicePaging=true`) is service paging, and therefore returns only max numbers of items equal to the passed `pageSize`. Client paging returns max numbers of items equal to the configured `maxHitsFromIndexingService(default 500)`. Consider the client paging option when filter providers are configured, and paging needs to be intact.

## Limitations

The Optimizely FTS Service handles plain text only and does not understand a markup language, such as HTML, and cannot calculate relevance based on markup (such as <h1> <b> and so on).

The Optimizely FTS Service does not crawl the web or update automatically. Indexed content is pushed into the service and thus hands over the responsibility of keeping the index updated to the client.

## Third-party search engines

The loose couplings between the FTS Client and Service allows for third-party search engines to implement solutions compatible with the FTS Client independent of platform. The only requirement is to comply with the REST service endpoint specifications. For .NET environments, override the `UpdateIndex`, `GetSearchResults`, `GetNamedIndexes` and `ResetNamedIndex` methods in the `IndexingServiceHandler`, thus using the existing WCF REST service implementation.