A query result enumerator
Created by c4db_query. Must be freed with c4queryenum_free.
The fields of this struct represent the current matched index row.
They are valid until the next call to c4queryenum_next or c4queryenum_free.
The columns of this result, in the same order as in the query's `WHAT` clause.
NOTE: FLArrayIterator is member variable of C4QueryEnumerator. Not necessary to release.
public long getMissingColumns()
Returns a bitmap in which a 1 bit represents a column whose value is MISSING.
This is how you tell a missing property value from a value that is JSON 'null',
since the value in the `columns` array will be a Fleece `null` either way.