DROP-INDEX — Drop a database index.Function
nameThe name of the index as a string, symbol or SQL expression.
onThe name of a table as a string, symbol or SQL expression.
databaseA database object which defaults to *default-database*.
if-does-not-existA symbol. Meaningful values are :ignore or :error (the default).
Drops the index called name in
      database which defaults to
      *default-database*. If the index does not exist
      and if-does-not-exist is
      :ignore then drop-index
      returns NIL whereas an error is signalled if
      if-does-not-exist is
      :error. 
      
 
        The argument on allows the optional
        specification of a table to drop the index from. This is
        required for compatability with MySQL.
      
(index-exists-p [foo])
=> T
(drop-index [foo] :if-does-not-exist :ignore)
=> 
(index-exists-p [foo])
=> NIL