The Search API module supports a handful of data alterations and processors; additional operations that can be performed on a document before it's indexed or during the display of search results. While Solr actually handles the majority of these for us already, this tutorial will look at the available options, talk about what each one does, and explain which ones are still relevant when using Solr as a backend.
Looking at data alterations in the Search API module also raises an important point about security. By default, Search API doesn't care about your content's access control settings. In order to prevent people from seeing results for their searches that contain data they shouldn't have access to we need to make sure we account for that in our configuration.
Here's a good list of the currently available data alterations and processors, though it's worth noting that not all of them are available for all search backends. Also, as we'll see, not all of them are recommended when using Solr even if they are available. Solr's tokenizer for example is much more full featured than the Search API tokenizer, so when using Solr as a backend it's best to keep the Search API tokenizer turned off and let Solr do its thing.
By the end of this lesson you should be able to use data alterations and processors to filter out specific content types from your Solr index and to highlight keywords found when displaying search results. You'll also be able to explain why some alterations and processors are better left off so that Solr can handle those tasks directly.