MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
      The INNODB_FT_DELETED table stores
      rows that are deleted from the FULLTEXT index
      for an InnoDB table. To avoid expensive index
      reorganization during DML operations for an
      InnoDB FULLTEXT index, the
      information about newly deleted words is stored separately,
      filtered out of search results when you do a text search, and
      removed from the main search index only when you issue an
      OPTIMIZE TABLE statement for the
      InnoDB table. For more information, see
      Optimizing InnoDB Full-Text Indexes.
    
      This table is empty initially. Before querying it, set the value
      of the innodb_ft_aux_table system
      variable to the name (including the database name) of the table
      that contains the FULLTEXT index; for example
      test/articles.
    
For related usage information and examples, see Section 14.16.4, “InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables”.
      The INNODB_FT_DELETED table has these
      columns:
    
          DOC_ID
        
          The document ID of the newly deleted row. This value might
          reflect the value of an ID column that you defined for the
          underlying table, or it can be a sequence value generated by
          InnoDB when the table contains no suitable
          column. This value is used when you do text searches, to skip
          rows in the INNODB_FT_INDEX_TABLE
          table before data for deleted rows is physically removed from
          the FULLTEXT index by an
          OPTIMIZE TABLE statement. For
          more information, see Optimizing InnoDB Full-Text Indexes.
        
mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_FT_DELETED;
+--------+
| DOC_ID |
+--------+
|      6 |
|      7 |
|      8 |
+--------+
          You must have the PROCESS
          privilege to query this table.
        
          Use the INFORMATION_SCHEMA
          COLUMNS table or the
          SHOW COLUMNS statement to view
          additional information about the columns of this table,
          including data types and default values.
        
          For more information about InnoDB
          FULLTEXT search, see
          Section 14.6.2.4, “InnoDB Full-Text Indexes”, and
          Section 12.9, “Full-Text Search Functions”.