Certain statements and fields automatically exclude a query from consideration for a firehose or firehose block cursor. For example:

  • FOR FIRST and FOR LAST statements. These statements return at most one row, so they are optimized with the Transact-SQL keyword TOP, which renders them ineligible for a firehose cursor.

When the DataServer is unable to implement Firehose or Firehose block cursors, the server-side Fast Forward-only (FFO) cursors are implemented. For information about FFO cursors, see Fast Forward-Only cursors.