Force reindexing of one or all search indexes, without deleting existing index data.
drush search-api-reset-tracker
index_id : The machine name of an index
Schedule all search indexes for reindexing.
drush search-api-reindex
Alias to schedule all search indexes for reindexing .
drush sapi-r
Schedule the search index with the ID node_index for reindexing.
drush sapi-r node_index