Name
WPSOLR_Events::WPSOLR_FILTER_INDEX_SANITIZE_FIELD
Short description
Sanitize a field value.
Long description
Control that a field value matches it’s expected Solr type definition. Often, your custom fields contain some historical irrelevant values, like a string when a number is expected, which can lead to Solr errors while indexing. With this filter, you can stop the indexing, or simply ignore the field value.

Examples
Search in the plugin's code (we eat our own dog food).